teaching of science

TEACHING OF SCIENCE AT UPPERPRIMARY LEVEL

Distance Education Programme -Sarva Shiksha Abhiyan(DEP-SSA)

(An IGNOU-MHRD, Govt. of India Project)IGNOU, Maidan Garhi, New Delhi - 110 068

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February 2010

© Distance Edcation Programme-Sarva Shiksha Abhiyan, IGNOU, 2010

Printed at: Gita Offset Printers, C-90, Okhla Industrial Area, Phase-I, New Delhi-110020

ALL RIGHTS RESERVED� No part of this publication may be reproduced, stored in a retrieval system or

transmitted in any form or by any other means - electronics, mechanical,photocopying, recording or otherwise without the prior permission from thepublishers.

� This book is an unpriced publication and shall not be sold, hired out or otherwisedisposed of without the publisher's consent, in any form of binding or coverother than that in which it is published.

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Guidance

Prof. K.R. Srivathsan Dr. S.S. JenaPro Vice-Chancellor, IGNOU Former Project DirectorDirector, DEP-SSA, IGNOU DEP-SSA, IGNOU

Academic Coordination

Dr. Hema PantProgramme OfficerDEP-SSA, IGNOU

Editors

Prof. S.C. Agarkar, Dr. C.K. Ghosh,Homi Bhabha Centre for Director, Student Services Centre,

Science Education, IGNOU, New DelhiTIFR, Mumbai

Distance Education Programme -Sarva Shiksha Abhiyan(DEP-SSA)

(An IGNOU-MHRD, Govt. of India Project) IGNOU, Maidan Garhi, New Delhi - 110 068

iv

Dr. M.K. Dash,Programme Officer, DEP-SSA, IGNOU, New Delhi

Prof. S.C. Agarkar, Homi BhabhaCentre for Science Education, TataInstitute of Fundamental Research,Mankhurd, Mumbai – 400 088

Mr. Binay Pattnaik,Consultant, TSG,

EdCIL, New Delhi

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CONTENTS

Page No.Acknowledgement vi-viiAbout the Module viii-xi

BLOCK 1 SCIENTIFIC CONCEPTS 1

Unit 1 Acids, Bases and Salts 3-13

Unit 2 Metals and Non-Metals 14-23

Unit 3 Energy (Heat and Light) 24-39

Unit 4 Plant Cell and Animal Cell 40-45

Unit 5 Environment 46-64

BLOCK 2 SCIENTIFIC PRINCIPLES 65

Unit 1 Chemical Reactions 67-76

Unit 2 Modified Root, Stem and Leaf 77-89

Unit 3 Circulatory System 90-99

Unit 4 Biodegradation, Solid waste management, Vermincomposting and Rainwater harvesting 100-116

BLOCK 3 SKILL OF PERFORMING SCIENTIFIC EXPERIMENTS 117

Unit 1 Experiments in Science 118-140

Unit 2 Respiration, Food adulteration, Transpiration and Use of Microscope 141-157

Unit 3 Purification of Water, Artificial Greenhouse and Model of Rainwater Harvesting 158-165

Unit 4 Science Corner 166-184

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ACKNOWLEDGEMENT

Sarva Shiksha Abhiyan (SSA), is a major initiative of the Government of India to universalize elementaryeducation, in all the 35 States and Union Territories of the country. Distance Education Programme(DEP)has been carved out within the SSA by the Ministry of Human Resource Development, GOI, to augmentits efforts in this mission using the open and distance learning mode. The Indira Gandhi National OpenUniversity which is the national apex body for maintaining and coordinating standards of open anddistance education in the country, has been entrusted with the responsibility of providing the necessarytraining to elementary level functionaries working in DIETs, SCERTs, BRCs, CRCs. DEP-SSA, IGNOU,thus works as a national resource centre, to empower elementary level functionaries, in developingappropriate skills and competencies for qualitative enhancement of classroom practices and for effectivecurricular transactions.

As a step in this direction DEP-SSA has developed a training module (self-instructional) for scienceteachers at upper primary school level, based on the constructivist pedagogy. The National CurriculumFramework 2005 has emphasized the constructivist approach which encourages students to usetechniques like experiments, solving real world problems, reflective learning and engaging in debatesand discussion with peers and teachers to arrive at new ideas and theories. Such a classroom culturefacilitates independent thinking and fosters the urge to address and solve problems in multiple ways.The focus of curricular transactions shifts from rote learning and memorization to learning by doing,experiential learning, collaboration, discussions and exploration. An attempt is made in this module tosensitize science teachers towards such learner centric approaches for elementary level learners.

DEP-SSA, IGNOU, acknowledges the contributions of the individuals and organizations involved inthe development of this module.

� Department of School Education and Literacy, MHRD, Government of India, for entrusting DEP-SSA with the responsibility of enhancing the professional competencies of elementary educationfunctionaries of SSA.

� Prof. V.N. Rajasekharan Pillai, Vice Chancellor, IGNOU, for his constant motivation,encouragement and support throughout the year for all DEP-SSA activities.

� Prof. K.R. Srivathsan, Pro Vice Chancellor, IGNOU and Director DEP-SSA, for his invaluableguidance and untiring efforts through useful academic interventions for all DEP-SSA initiatives.

� Dr. S.S. Jena, former Project Director, DEP-SSA, and presently Chairman NIOS, for being theguiding spirit in this enterprise and for providing unflinching support, right from the stage ofprogram designing, unit writing to editing of module.

� All members of the Programme Design Committee for their valuable inputs in giving the desiredshape to the module.

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� All members of the Expert Guidance team for a meticulous review of the module structure.

� Prof. S.C. Agarkar, Homi Bhabha Center for Science Education, TIFR, Mumbai, for contentediting of the module.

� Dr. C.K. Ghosh, Director, Student Services Centre, IGNOU, for painstakingly doing the content,language and format editing of the module.

� All the faculty and staff of DEP-SSA, who were always forthcoming with their help andcooperation in bringing out this document.

I sincerely hope that this training module will provide useful insights to all concerned with teachingscience at the elementary school level. I look forward to your feedback and constructive suggestionsfor further improvement in the module.

February, 2010Project Director

DEP-SSA, IGNOU

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ABOUT THE MODULE

Science education at the Upper Primary level should provide the opportunity of learningby doing to the children. The teacher should engage children in such activities that enablethem to make sense of the world around. Learning experiences provided should be suchthat develop scientific concepts through activities, experiments, using easily availableand inexpensive resources. The pedagogic practice at this stage should focus on meaningfulinvestigations, based on hands-on experience, group discussions guided by the teacherand peer interactions. Acquisition of skills, scientific temper and appreciation for scienceshould be the major concern, so that learning becomes a continuous process, even beyondschool. NCF 2005 has emphasized the need to strengthen science education so that childrenare enabled to examine, analyze and develop the spirit of enquiry. In order to realize thegoal of science education at elementary level, it is necessary to empower the scienceteachers and improve their professional skills. With this in mind, DEP-SSA has developeda teacher training module for science teachers at upper primary level in the self-instructionalstyle. This document will serve as support material for science teachers since it is basedon the NCERT science curriculum at upper primary level. The main objectives of thetraining module are to:

� improve professional competencies of teachers to teach science at upper primarystage.

� enable teachers to engage children in learning scientific concepts and principlesthrough experiential learning.

� enable teachers to organize group activities, discussions, projects, to facilitatelearning of elementary science in the classroom.

� facilitate teachers to develop interest, curiosity in learning science and build scientifictemper in students at the elementary stage.

The document, entitled "Teaching of Science at Upper Primary Level" is written in self-instructional style. The module compiled in one volume, comprises 13 units, arranged inthree blocks - Block 1, 2 and 3. A brief description of each Block is given below:

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BLOCK 1: SCIENTIFIC CONCEPTS

This block consists of five units. Each unit deals with some scientific concepts. Teacherswill undertake some activities and experiments and engage students in the classroom toarrive at these concepts. The five units in this Block are

Unit 1: Acids, Bases and Salts

The concepts of acids, bases and salts are discussed through activities. Understanding ofthese will lead to identification of substances as acids, bases and salts. Their propertiesand the process of neutralization and its applications in daily life are presented.

Unit 2: Metals and Non-Metals

Physical and chemical properties of metals and non-metals are described through variousexperiments and activities. The teacher can differentiate the concepts of metals and non-metals on the basis of their properties. Common uses of metals and non-metals are alsopresented, based on daily life experiences.

Unit 3: Energy (Heat and Light)

The unit deals with the concepts of heat and light as forms of energy. Some strategiesare presented which will enable the teachers to differentiate these concepts throughexamples and illustrations in the classrooms and describe their properties.

Unit 4: Plant Cell and Animal Cell

Structure of the cell and differences between plant and animal cell are presented. Theconcepts provided in the unit will enable teachers to prepare simple slides of plant (onion)cell and animal (cheek) cell and observe them under the microscope in the classroom.The activities will enable them to demonstrate these concepts in the classroom by engagingchildren and develop skill of observations & differentiation.

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Unit 5: Environment

The unit discusses some current environmental issues, their causes, effects and preventivemeasures. Various concepts in the area of environment, like pollution and its types,green house effect, ozone hole and environment conservation are presented throughactivities.

BLOCK 2: SCIENTIFIC PRINCIPLES

Some scientific principles based on concepts discussed in the units of Block -1 arepresented in this module. Some of the principles are explained using activities,experiments and discussions. These units will facilitate science teachers at the elementaryschool level to transact science lessons, using the 'Learning by doing' approach. A briefoverview of each of the four units 1 to 4 of Block is presented below:-

Unit 1: Chemical Reactions

The importance of physical and chemical changes in daily life is explained in this unit.Various types of chemical reactions which describe the chemical changes and balancingthe chemical reactions are discussed through activities. The processes of crystallizationand solubility are described.

Unit 2: Modified Root, Stem and Leaf

Teachers will be able to organize group activities with children in the classroom to explainthe root system, shoot system and their various modifications. The unit also explains thevarious functions performed by the modified roots and stems.

Unit 3: Circulatory System

Principles of blood circulation are discussed in the unit. Several activities to be performedby students are presented through which they can recognize and identify different partsof the circulatory system of the human body. Some of the activities in the unit explainthe process of blood circulation.

Unit 4: Biodegradation, Solid Waste Management, Vermicomposting, Rain WaterHarvesting.

This unit aims to sensitize learners about the harmful effects resulting from the overuseand abuse of nature's resources. Some practices are discussed which help to identify anddifferentiate between healthy and harmful human activities. Experiments and activitiesare presented to explain the principles of biodegradation, vermicomposting, solid wastemanagement and rain water harvesting.

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BLOCK 3: SKILL OF PERFORMING SCIENTIFIC EXPERIMENTS

The primary objective of science education, particularly at the upper primary stage is todevelop curiosity, critical thinking, logical reasoning and an appreciation for science.All the units (1 to 4) in this block deal with scientific experiments, with active involvementof students, in the classroom. A brief summary of each unit is presented below:

Unit 1: Experiments in Science

This unit explains strategies of teaching scientific experiments, through variousexperiments pertaining to separation of substances, reactions of acids, bases and saltsand properties of metals and non-metals. The teacher will be empowered to performscientific experiments in the classroom using multiple ways.

Unit 2: Respiration, Food Adulteration, Transpiration and Use of Microscope

The process of transportation of useful materials and excretion of wastes in plants andanimals is described. Different types of transportation in plants and animals, and causesand types of food adulteration are explained through experiments and activities. Structureand use of microscope is presented.

Unit 3: Purification of Water, Artificial Green House, Model of Rain WaterHarvesting

The experiments and working models described in this unit will further strengthen someconcepts taught to the students in the previous blocks. The experiments relate to theconcepts and principles pertaining to purification of water, rain water harvesting,greenhouse gas emissions and vermicomposting.

Unit 4: Science Corner

The unit discusses the need of a science corner in the elementary classroom. The activitiesdiscussed will enable the teachers to create a science corner in the classroom using lowcost materials, specimens and models. The processes involved in building up the sciencecorner through student involvement are described. Teachers will be equipped to performactivities that involve use of experimental cards, making charts, posters and develop ascience kit for performing simple experiments.

Block

1SCIENTIFIC CONCEPTS

1. Unit 1Acids, Bases and Salts 3-13

2. Unit 2Metals and Non-Metals 14-23

3. Unit 3Energy (Heat and Light) 24-39

4. Unit 4Plant Cell and Animal Cell 40-45

5. Unit 5Environment 46-64

UNIT 1 ACIDS, BASES AND SALTS

Structure

1.1 Introduction1.2 Objectives1.3 Acids

1.3.1 Properties of Acids1.3.2 Basicity of Acids1.3.3 Uses of Acids

1.4 Bases1.4.1 Properties of Bases1.4.2 Acidity of Bases1.4.3 Uses of Bases

1.5 Indicators1.6 Salts1.7 Neutralization1.7.1 Neutralization in daily life.1.8 Let Us Sum Up1.9 Answers to Check Your Progress1.10 Glossary1.11 References

1.1 INTRODUCTION

A common kind of ailment after you have heavy or spicy food is acidity.We say that there has been formation of acid in the stomach. It can beneutralized by the action of some base. Acids on the other hand play acrucial role in our life. A very common use is in cleaning the toilets.

Bases are used profusely in the soap and detergent industry. In other words,we depend on bases for keeping other bodies, clothes clean.

And we are all familiar with the common salt which we use for cooking.The word salt has a different connotation in chemistry. However, thecommon salt, sodium chloride is also a salt.

In this unit, you will be able to identify and categorize substances intoacids, bases and salts and learn their uses. You will also learn to preparenatural indicators from local resources for identification of acids and basesand their acidity and basicity. You will be able to explain the concept ofneutralization and understand its application in daily life.

1.2. OBJECTIVES

After studying this unit, you will be able to� identify acids, bases and salts.� tell the important properties of acids, bases and salts.� differentiate between acids, bases and salts� prepare natural indicators from locally available substances.

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Scientific Concepts � identify substances as acidic and basic based on their reactions withindicators

� identify applications of neutralization in daily life.

1.3 ACIDS

We shall begin our discussions with an activity.

Activity - 1You ask the students to recall the taste of different edible substances in theirdaily life and find out whether their tastes are similar or different. Mentionthe taste of each of these substances if they have never tasted them earlier.You can undertake the activity now.

Caution: You will tell your students to observe these precautions� Never taste a substance unless asked to do so.� Never touch anything unless asked to do so.After undertaking the activity you may present the results in the followingtabular form.

Table 1.1: Classification of substances based on table(sour, salty, sweet, bitter)

S. No. Substanc Taste(Sour/Bitter/Sweet/Salty)

1. Vinegar Sour2. Lemon juice Sour3. Sugar Sweet4. Curd Sour5. Common Salt Salty6. Cocoa Bitter7. Grapes Sour8. Amla Sour9. Baking Soda Bitter10. Tamarind Sour

Acids are substances that give Hydrogen ion (H+) as the only positive ionon dissolving in water. The word acid is derived from the Latin word aciduswhich means sour. So, in chemistry, the group of compounds having sourtaste and which gives H+ ions in solution are known as acids.

HX = H+ + X-(aq) (aq) (aq)

All acids can be classified into the following categories

A. Naturally occurring AcidsThe naturally occurring acids are weak acids. Many of our food itemscontain such weak acids in varying amounts.

Activity 2� Students will sit in a circle.

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Acids, Bases and Salts� Then you ask the students to tell the name of some fruits/vegetables,which taste sour.

� Further ask them - why these taste sour?� With the help of students, you will consolidate: Lemons, oranges,

raw-mangoes, etc. are sour in taste due to the presence of acids inthem

B. Mineral acidsMineral acids are strong acids. Sulphuric acid (H

2SO

4), Hydrochloric

acid (HCl), Nitirc acid (HNO3), etc. are some commonly used mineral

acids. These acids are called mineral acids because these are preparedfrom minerals. Mineral acids are very important from the industrialpoint of view. These are used in the manufacture of fertilizers,explosives, dyes etc.

Activity 3� Students will be divided into groups� To each group, give the juice of half a lemon and blue litmus paper� Ask the students to put blue litmus paper in lemon juice� Ask the students to note down the observation viz. change in color

etc.� With the help of students you will consolidate - acid turns blue litmus

paper into red color.

Today we encounter these directly or indirectly in daily life.

o All fruits contain acids and so do many common foods.o Cold drinks contain some carbonic acid which gives tingling taste.o Apples contain malic acido In lemon, oranges and grapes there is citric acid.o Souring of milk produces lactic acid.o Digestion of food in our body depends on the presence of hydrochloric

acid.

1.3.1 Properties of Acids

� All acids have a sour taste.� All acids turn blue litmus red.� Acids give Hydrogen ion (H+)

on dissociation.e.g. H

2SO

4, HCl, HNO

3

� Concentrated mineral acids suchas sulphuric acid, nitric acidattack human tissues, clothes,paper and metals. The naturallyoccurring acids attack metalsslowly producing toxiccompounds.

Every acid has replaceable hydrogen atom (s), which when replaced bymetals or radicals, produces salts.

The property of an acid withreference to the replaceablehydrogen atom should not beused as the definition of acid.Otherwise, a salt like SodiumHydrogen Sulphate (NaHSO4)may seem like an acid as itcontains a replaceable H-atomwhich is replaced by Na, givesthe salt, Na

2SO

4.

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Scientific Concepts 1.3.2 Basicity of AcidsThe number of replaceable hydrogen atoms in an acid is called thebasicity of the acid. e.g. If an acid has one replacable H, its basicityis one or is monobasic e.g. HCl. Similarly H

2SO

4 is dibasic as it

has two replacable H-atoms. The basicity of H3PO

4 is three or it is

a tri-basic acid and so on.

1.3.3 Uses of AcidsHydrochloric, nitric and sulphuric acids are very important acidsfrom the commercial point of view. Some important uses of theseacids are mentioned below:

� Hydrochloric acid (HCl):i. For the preparation of chlorides and chlorine gas.ii. For cleaning iron sheets before galvanizationiii. For extracting glue from bones.iv. In textile industry for dyeing

� Nitric acid (HNO3) :i. For preparing fertilizers, explosives, dyes and drugsii. In the refining of gold and silver

� Sulphuric acid (H2SO4)i. For preparing fertilizers, detergents, plastics, synthetic fibresii. In petroleum industry for refining.iii. In lead-acid batteries (as electrolyte).

CHECK YOUR PROGRESS 1

Note: a) Write your answers in the space given belowb) Compare your answers with those given at the end of the

unit.

1. Which colour will a litmus paper turn to if it is dipped in anacid?

2. Mention one use of each of HCl, H2SO

4, and HNO

3

Now that you have learnt about acids, let us go over to study bases.

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Acids, Bases and Salts1.4 BASES

Bases are substances that give hydroxyl (OH-) ions on dissolving in water.There are oxides and hydroxides, for example Na2O, NaOH. Bases arebitter in taste and soapy to touch.Metals like Na, K and Ca react with water and H2 gas is liberated in eachcase and NaOH, KOH and Ca (OH)

2 are respectively formed. The bases

which are soluble in water and contain hydroxide ions (OH-) in theirmolecules are called alkalies. Sodium hydroxide (NaOH), Potassiumhydroxide (KOH), Calcium hydroxide (Ca (OH) 2) and Barium Hydroxide(Ba(OH)2) are alkalies.

All alkalies are bases but all bases are not alkalies. For example, Na2O is a

base but it is not an alkali.

When you overeat or take highly spiced fried food your stomach gets upsetand you take an antacid. Antacids are prepared from weak bases likealuminium hydroxide and magnesium hydroxide.

1.4.1 Properties of bases1 Bases are compounds that contain hydroxyl groups2 All bases give hydroxyl ions in solution.3 Bases have bitter taste.4 Bases and alkali solutions are soapy to touch5 Bases turn red litmus blue.6 Bases react with acids to give salt and water

NaOH + HCl = NaCl + H2O

Base acid salt water

Activity 4Ask the students to rub a little solution of caustic soda betweentheir fingers. Ask them what type of feeling do they get? What dothey infer?

1.4.2 Acidity of BasesThe number of replaceable hydroxyl (OH-) ions in a base is calledthe acidity of that base, e.g. KOH and NaOH each have onereplaceable hydroxyl group, hence its acidicity is one and we call itmono-acidic. Similarly, the acidity of Ca (OH)

2 is two, or it is di-

acidic. The acidity of Al (OH) 3 is three or it is tri-acidic and so on.

1.4.3 Uses of Bases

The uses of some typical bases are described below:� Sodium hydroxide (caustic soda) (NaOH) :

i. In soap and detergent industryii. For the manufacture of rayoniii. In paper and pulp industryiv. For manufacturing other chemicals.

� Calcium hydroxide (slaked lime) (Ca(OH)2 )

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Scientific Concepts i. For white washingii. For the manufacture of bleaching powderiii. In leather industryiv. For neutralizing acidity of the soilv. For softening hard water

� Ammonium hydroxide (NH4OH)i. As a cleansing agentii. For preparing ammonium salts

� Aluminium Hydroxide (Al(OH)3 )i) For preparing antacid

CHECK YOUR PROGRESS 2Note: a) Write your answers in the space given below

b) Compare your answers with those given at the end of theunit.

. 1. Give two examples each of acidic and basic substances andname the acid/base found in them.

Now that you have studied acids and bases, we shall take up discussion onIndicators.

1.5 INDICATORS

Let us start our discussion with an activity.

Activity 5

Step 1 Take a blotting paper and rub the petals of China rose floweron it. Now cut the purple coloured blotting papers into thinstrips. This will be the indicator (litmus paper) prepared froma natural substance (China rose)

Step 2 Take three glass beakers. To each add 20 ml water. Labelthem as cup 1, 2 and 3. In cup 2 add some vinegar and in cup3 add baking soda.

Step 3 Place the three cups next to each other so the class can seethem.

Step 4 Ask the class to record their observations when an indicatorstrip is dipped in each of these cups.

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Acids, Bases and SaltsTable 1.2: Reaction of Indicator with different types of substances(Acids, Bases & Salts)

S. Test Solution Effect on indicator InferenceNo. (litmus paper)1 Cup 1 No effect Neutral2 Cup 2 (Vinegar) Turns dark pink Acidic3 Cup 3 (Baking Soda) Turns Green Basic4 Cup 4 (Common Salt) No effect Neutral5 Cup 5 (Sugar Solution) No effect Neutral6 Cup 6 (Lemon Juice) Turns dark pink Acidic

You will ask the students to name those substances, which had no effect onthe indicator paper.

These are neutral solutions, which are neither acidic nor basic.

Another example of natural indicator is turmeric (haldi). Turmeric paste,made by mixing turmeric powder and some water, can be rubbed on ablotting paper and dried. This can be used as an indicator for acids andbases.

Activity 5Prepare a greeting card using turmeric paste. Take a white sheet of paper.Apply turmeric paste and allow it to dry. Draw a design on the dried paperwith soap solution, using a cotton swab. What colour design do you get?Soap solution is basic and hence turmeric changes to red colour.

Now answer this question -



1. Why does a turmeric stain on your white school dress turn red,when washed with soap?

Thereafter you will ask students to give names of indicators used in thelaboratories.

They are(i) Litmus Solutions and Litmus Paper (Blue and Red Litmus)(ii) Phenolphthalein

Let us now learn about salts.

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Scientific Concepts 1.6 SALTS

A substance formed by the neutralization reaction of an acid with base iscalled salt. Acids react with alkalies to form salt and water. This process iscalled neutralization reaction. In this process addition of acid destroys thealkaline property; addition of alkali destroys the acidic property. Theresulting solution is neither acidic nor basic.

NaOH + HCl = NaCl + H2O(Base) (Acid) (Salt) (Water)

Activity 6Take about 5 ml each of dil HCl, and dil. H

2SO

4 in different test tubes and

add a piece of magnesium ribbon to each of the test tubes. What do youobserve?

Test the gas by bringing a burning splinter near the mouth of each test tubeand write down your observations.

Let us now study Neutralization

1.7 NEUTRALIZATION

We shall start with an activity.

Activity 7You will perform the following experiment and students will answer andrecord observation.1 Take a test tube and fill it one fourth with dilute hydrochloric acid.2 What is the colour of the solution? (Colourless)3 Now add 2-3 drops of phenolphthalein indicators.4 What is the change in colour of solution (remaining colourless solution)5 To this acidic solution, add a drop of sodium hydroxide solution and

stir the solution.6 Is there any change in colour of solution?7 Continue adding sodium hydroxide solution drop by drop till the pink

colour just appears.8 Now add one more drop dilute hydrochloric acid. What do you observe?

(solution becomes colourless)9 Add a drop of sodium hydroxide solution. Do you observe change in

colour? (Solution becomes pink)10 What do you conclude? When the solution is basic, phenolphthalein

gives pink colour and when solution is acidic it remains colourless.11 What happens when an acidic solution is mixed with a basic solution?

They neutralize the effect of each other and the resulting solution isneither acidic nor basic.

12 Touch the test tube from outside, soon after neutralization reaction,How does it feel? (Hot)In neutralization reaction, heat is always evolved which raises thetemperature of the reaction mixture.

13 What is the new substance formed in neutralization reaction/(salt)

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Acids, Bases and Salts14 Can you derive the definition of Neutralization? It can be defined as:

The reaction between an acid and a base, to form salt and water, withthe evolution of heat, is called neutralization.

15. Give the general equation for neutralization (Acid + Base = Salt + Water (Heat is evolved))

1.7.1 Neutralization in Daily Life

We shall study neutralization in daily life using examples. Teacher will asksome questions based on students' daily life experiences

Example 1: Indigestion/Acidityi) Does human body contain acids? Yes/Noii) Name two acids present in the body? (Fatty Acids, Hydrochloric Acid)iii) In which part of the human body do we find hydrochloric acid?

(Stomach)iv) When do we experience (burning sensation) acidity? {Due to

indigestion/overeating, too much acid is formed in the stomach}v) What medicine do you take to get relief from indigestion? {Antacid

like Milk of Magnesia or Digene, The base present in the antacid (e.g.Magnesium hydroxide) neutralizes the acid in the stomach)

Example 2: Ant Bitei) What do you apply to the skin, when an ant bites? (calamine lotion,

moist baking soda}ii) Why do you feel the sting when the ant bites {the ant injects acid

(formic acid) in the skin, which causes the sting and pain}.iii) Why does application of calamine or baking soda, bring relief from the

sting. {Calamine which contains zinc carbonate and baking soda havingsodium hydrogen carbonate, neutralizes the effect of formic acid)



1. What will happen when dilute hydrochoric acid is added tosodium hydroxide solution?

2. What will happen to the temperature of the reaction mixture inthe test-tube?

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Scientific Concepts 1.8 LET US SUM UP

In this unit you learnt that� Acids have sour taste and bases have bitter taste.� Naturally-occurring acids are weak acids. These acids are present in

many food items.� Mineral acids are strong acids. These acids are obtained from minerals.� Bases have bitter taste, soapy touch and strong bases are corrosive to

skin.� All bases release OH- ion in aqueous solution� Bases turn red litmus to blue� Indicators are substances which change colour with acidic and basic

solution� Turmeric and china rose are some natural indicators� Substances which are neither acidic or basic are called neutral� An acid and a base when mixed, neutralizes each other to form salt and

water.

1.9 ANSWERS TO CHECK YOUR PROGRESS

Answer 11. Blue litmus paper turns red2. Uses of :

HCl – in textile industry for dyeingH

2SO

4 – preparation of fertilizers

HNO3 – manufacture of explosives

Answer 21.

Acidic Substances Grapes Curd

Acid Tartaric acid Lactic Acid

Basic Substances Lime Water Soap

Acid Calcium Sodiumhydroxide Hydroxide

Answer 31. The soap solution is basic and when turmeric in the stain comes into

contact with the base changes to red color.

Answer 41 It will form Sodium Chloride, i.e. salt and water2. The test tube becomes hot, i.e. the rise of temperature

1.10 GLOSSARY

Acid An acid is a substance that gives H+ (hydrogen) ions inwater. Acids have sour taste.

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Acids, Bases and SaltsBase A base is a substance that gives OH- (hydroxyl) ions inwater. Bases are soapy to touch.

Salt A salt is a substance formed by the neutralizationreaction of an acid and base.

Neutralization It is the reaction between an acid and base to producesalt and water with release of heat.

Indicator It is a substance, which gives different colours whenmixed with acid and base. The colours help one toidentify acids and bases. It is neutral.

1.11 REFERENCES

www.miamisci.org

NCERT, Science Text Book for Class VII (2007), New Delhi

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Scientific Concepts UNIT 2 METALS AND NON-METALS

Structure

2.1 Introduction2.2 Objectives2.3 Metals

2.3.1 Physical Properties2.3.2 Occurrence and Use of Metals2.3.3 Reactivity Series

2.4 Non Metals2.4.1 Physical Properties2.4.2. Occurrence and Use of Non Metals

2.5 Corrosion of Metals2.5.1 Methods of Preventing Corrosion

2.6 Let us Sum Up2.7 Answers to Check Your Progress2.8 Glossary2.9 References

2.1 INTRODUCTION

You must have observed serious concern about security measures at sensitiveplaces like airports, railway stations, and important tourist spots. The publiccongregating at such places are supposed to pass through a device calledMetal Detector. It is because a thing like a sharp weapon gets detected.Such an item can only be created out of a metal. This indicates that metalshave a special place in the study of materials. They are indeed distinctfrom the other variety, called non-metal.

In this unit you will learn about the properties, uses and occurrence ofmetals and non-metals. We will also discuss about the corrosion of metals.

2.2 OBJECTIVES

After going through this unit, you will be able to� identify the metals and non-metals� differentiate metals and non metals in accordance with their physical

properties� spell out the common use of metals and non-metals� explain difference in reactivity of different metals� describe the reason of corrosion of metals and its prevention

2.3 METALS

Activity 1� Students will sit in a circle.� You will ask them

15

Metals and Non-Metals� to write individually the list of things seen inside the classroom. Thenyou will divide students into small groups and ask them to prepare afinal list of things seen inside the classroom.

� Out of this list, you will ask the students to identify the things which aremetals.

� Each group will present the list of metals and you will lead the discussion.

There are more than 114 different elements known to us today. Lavoisierbroadly classified these elements into metals and non-metals by studyingtheir properties. Of these only 22 are non-metals. Properties of metals arequite different from those of non-metals.

A metal is an element which can form +ve ions (cations) by the loss ofelectrons. The number of electrons lost by an atom is known as the valencyof the metal.

Na = Na+ + e–

Mg = Mg+ + 2e–

Thus, sodium and magnesium are metals because they can form +ve ionsby the loss of electrons. Now, let us study the physical properties of metals.

2.3.1 Physical properties of metals

1. Metals have a metallic luster

Activity 2� Collect pieces of some common metals like iron, copper, aluminum

and magnesium. Observe their appearance and how they reflectlight. The reflection is different for each metal.

� The shine of light on a metal is called metallic luster.

2. Metals are generally hard, though some are softMost of them are hard like iron, aluminum etc. though potassium andsodium are soft and can be cut with a knife.

3. Metals are malleableThis means that the metals can be hammered into sheets.

Activity 3 (whole class discussion)� Students will sit in a circle� You will ask the students, "Have you seen a blacksmith working in

his foundry? How is he doing his work?"� Open discussion will be made - Blacksmith beats iron metal into

thin sheets for making various implements.� What are the other metals, which can be hammered into thin sheets?

It will be discussed in the class.� Metals like aluminum, gold, silver etc. are hammered into sheets

and used for making utensils and ornaments.

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Scientific Concepts 4. Metals are ductileThat means they can be drawn into wires. We all have seen electricwires made of copper and aluminium. Iron wires are used for fencing.Goldsmiths make gold thread by drawing gold into fine wires. Thisproperty of metals is called ductility. We say gold, silver, copper,aluminium and iron are ductile.

5. Metals are good conductors of heat.We use vessels made of aluminium and copper for cooking becausethey are good conductors of heat.

Activity 4 (Teacher demonstrated Activity)� Take one iron rod.� Try holding one end of an iron rod with the other end over fire.� After a little time, what you will feel? You can feel the rise in

temperature at your end of the rod also.

Activity 5� Take three rods - copper, iron and aluminium of equal diameter

and equal length.� Insert the rods into an iron container, so that equal lengths of the

rods are outside the container.� Coat the free ends of the rods with wax.� Fill the iron container with boiling water.

Observe that heat is conducted by the iron rod. But, different metals takedifferent time to conduct heat.

Observations

The wax on the rods starts melting. But the wax melts to different lengthson the three rods. It takes different time for the wax to completely melt onthe three rods.

6. Metals are good conductors of electricity

Activity 6� Set up an electric circuit� Hold a piece of copper metal between metallic crocodile clips.� Notice that the bulb glows.� Now repeat the experiment with a piece of iron, zinc, nickel, etc.� Record the observation

7. Metals are sonorous

Activity 7� Take two spoons. One made of steel and other made of iron.� Drop two spoons from a height.� Observe the sounds they make. Which of them produces a ringing

sound?All metals produce a ringing sound, i.e. all metals are sonorous.

17

Metals and Non-Metals8. Metals generally have a high tensile strengthTensile strength means the greatest longitudinal stress a substance canbear without tearing apart.

Activity 8� Take one piece of paper on plastic� Try pulling both ends of the piece of paper on plastic.� What you will observe - It will easily tear and break.� Now try to break iron, copper and aluminum wire. They do not

break. It shows that metals are strong.9. Metals are usually solids

Mercury is the only metal in liquid form at room temperature. Allother metals exist in solid form at room temperature.


b) Compare your answers with those given at the end ofthe unit.

1. Give one example of a metal which(i) is liquid at room temperature.(ii) can be easily cut with a knife.(iii) is the best conductor of heat.

2.3.2 Occurrence and use of MetalsA mineral from which a metal can be extracted conveniently andprofitably is called an ore. Normally ores are found fixed with a lotof impurities such as soil and rocks. The quantities of impuritiesvary and where there are fewer impurities, they are called high-gradeores. The impurities are called gangue.

Uses of Common Metals

a. Uses of Iron: Iron is used for making pipes, sinks, cylinders, stoves,agricultural implements. It is also used for making cores of electromagnet.Iron is converted to different kinds of steels. The steel is used for makingtools, ships, bridges, etc.

b. Uses of Aluminum: It is used for making paints and mirrors, utensils,electrical wires, etc. Since it is a light metal, it is used for making thebody of ships, cars, etc.

c. Uses of copper: It is extensively used for making electric appliances,for making certain alloys like brass, bronze and German silver.

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Scientific Concepts d. Uses of Lead: It is used for making lead pipes and containers for corrosiveliquids. It is used in storage batteries. Underground telephone cablesare protected by lead covering.

Activity 9� Students will be divided into small groups� To each group, 4 chits will be given. In each chit, iron, aluminum,

copper & lead will be written.� Students will discuss in groups and write down the uses of these

metals.� Each group will present it and follow up discussion will be made in

the class.

Now that you have learnt about the different physical properties and usesof metal, let us go over to study the chemical properties.

2.3.3 Reactivity series

All metals are not equally reactive. Some metals are more reactive thanothers. Metals which lose electrons more readily to form +ve ions are morereactive. Less reactive metals do not lose electrons easily. Some metalsreact vigorously with an element or compound, some react slowly, whilesome do not react at all. Based on their reactivity, metals have been arrangedin a series in order of their decreasing reactivities. This order is calledreactivity series. In this series, the most reactive metal is placed at the topand the least reactive metal at the bottom.

Reactivity series of Metals

K Potassium Most ReactiveNa SodiumCa CalciumMg MagnesiumAl AluminumZn ZincFe Iron ReactivityPb Lead decreasesH HydrogenCu CopperHg MercuryAg SilverAu GoldPt Platinum Least Reactive

19

Metals and Non-Metals

Activity 10� Take an iron nail in a beaker containing a solution of CuSO4.� Remove the nail after some time. What do you observe?� There is a coating on the surface of the nail and the blue colour of

CuSO4 has turned green.

Fe + CuSO4 = FeSO

4 + Cu

In this reaction iron replaces Cu because iron is more reactive than Cu.

Activity 11Take a strip of copper in a solution of iron sulphate. Remove the strip of Cuafter some time. What do you observe?

� The blue colour of CuSO4 is not changed. This means that Cu can notreplace iron from iron sulphate solution. This proves Cu is less reactivethan Fe.

2.4 NON-METALS

There are 22 elements which are non-metals out of these 11 exists as gas,10 as solids and only one i.e. bromine occurs as liquid at room temperature.Some of the important non-metals are nitrogen, oxygen, hydrogen, helium,sulphur, bromine, carbon, neon etc.



1 Why sodium is kept immersed in kerosene oil?

2 Which is the most reactive metal?

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Scientific Concepts 2.4.1 Physical properties of non-metals.

1. Physical state: Non-metals exist in all the three states i.e. solid (carbon,phosphorous, sulphur), liquid (bromine) and gaseous (oxygen, hydrogen,nitrogen).

2. Non-lustrous: Most of the non-metals are non-lustrous and dull suchas sulphur, phosphorous. Graphite, diamond and iodine crystals areexceptions as they shine.

3. Soft and brittle: The solid non-metals are soft and brittle such asgraphite, sulphur and iodine. Only diamond, a form of carbon is hard.In fact, diamond is the hardest substance.

4. Low-density, melting point and boiling point: Since most of the non-metals are gases at room-temperature and are soft, their density is lowand therefore, their melting and boiling points are also low. Diamond isan exception as it is hard and its density, melting and boiling points arehigh.

5. Non-metals are not malleable or ductile: Being soft and brittle, nonmetals can not be converted into thin sheets or wires

6. Bad conductors of heat and electricity: Non-metals do not possessfree electrons to carry charge or heat and hence are poor conductors ofheat and electricity.



1. Why are non-metals bad conductors of electricity?

2.4.2 Occurrence and uses of non-metals

In free state, hydrogen is found in the mixed form with coal gas.Free hydrogen is found in the sun and stars. In combined form,hydrogen is found in natural gas, petroleum and in water.

In free state, nitrogen is found in the air. In combined state, nitrogenis found as a constituent of animal and plant protein.

In free state carbon is found as graphite, diamond and coal. Incombined state it is found in many organic compounds.

21

Metals and Non-MetalsHydrogen is used in the oxy-hydrogen torch which is used forwelding purposes. A mixture of hydrogen and helium is used inweather observing balloons.



1. Name a non metallic element which conducts electricity?

Activity 12� Divide the students into groups� Ask the two groups to sit face-to-face� One group will tell the name of one non-metal and other group will tell

its uses. Likewise the activity will go on.� You will provide support whenever required



1. What happens when a strip of copper is immersed in a solutionof iron sulphate?

2.5 CORROSION OF METALS

You must have seen a reddish-brown coating which forms on unprotectediron. This reddish-brown coating is called rust. Rust is caused by slowcombustion reaction which occurs when iron is in contact with both oxygenand moisture.

This surface chemical action in metals exposed to air and water is calledcorrosion. Both air and moisture must be present for corrosion to takeplace. The rusting of iron is an example of corrosion.

22

Scientific Concepts Effects of corrosion

Rust is soft and flaky. Once a layer of rust is formed it flakes off, leaving afresh surface to be attacked. This continuous processes result in thinning,weakening and eventually disintegrating the metal. Corrosion is thus awasteful process. It also weakens the metals.

2.5.1 Methods of preventing corrosionCorrosion can be prevented if the contact between metal and air iscut off. Some of the methods are:a) Coating with oils & grease -

Iron & steel instruments and parts of various machines arekept smeared with oils when not in use as this preventscorrosion as the metal is not in contact with air.

b) Coating with paintsCoating railway coaches, bridges, automobiles, etc with paintprevents corrosion.

c) Coating with other metals -Sometimes metals are coated with non-corrosive metals� Galvanising - A process of giving a thin coating of Zn on

iron sheets to prevent rusting.� Tinning - A process of giving a coating of tin.� Electroplating - In this method metal surfaces are covered

with another metal by using electric current & thuscorrosion is stopped. Many presentation articles, medalsetc are gold plated or silver plated electrolytically.

� Anodising - A process in which metals like Al, Cu, etc.are coated electrically with a thin and strong film of theiroxides which protects them from corrosion.

� Alloying - An alloy is a homogenous mixture of two ormore metals, or a metal and a non-metal. If one of themetals is mercury, then the alloy is known as an amalgum.Some metals when alloyed with other metal become moreresistant to corrosion. Stainless steel is an alloy of ironwhich does not rust.

2.6 LET US SUM UP

In this unit you learnt that� A metal is an element which can form positive ions by the loss of

electron.� Metals are generally hard.� Metals are malleable and ductile� Metals are good conductors of heat and electricity� Non-metals exists in gaseous, solids and also in liquid form� Non-metals are not malleable or ductile.� Non-metals are bad conductor of heat and electricity.� All metals are not equally reactive.

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Metals and Non-Metals2.7 ANSWERS TO CHECK YOUR PROGRESS

Answer 1(i) Mercury(ii) Sodium(iii) Copper

Answer 21. Sodium is very reactive when exposed to air or in water.

Hence it is stored in kerosene oil.2. Potassium

Answer 31. Non-metals are poor conductors of electricity because their

valence shell does not contain free electrons except graphite.

Answer 41. Carbon

Answer 51. No reaction will take place because copper is less reactive

than iron and therefore, cannot replace iron from iron sulphate.

2.8 GLOSSARY

Malleability Property of metals by which they can be beaten intothin sheets.

Ductility Property of metals by which they can be drawn intothin wires.

Sonorous Property of metals by which they produce a ringingsound.

Metals Substances which are hard, shiny and are goodconductors of heat and electricity.

Non-metals Soft and dull substances which are poor conductorsof heat and electricity.

2.9 REFERENCES

NCERT, Science Text Book for Class VIII (2008), New Delhi

24

Scientific Concepts UNIT 3 ENERGY (HEAT & LIGHT)

Structure

3.1 Introduction3.2 Objectives3.3 Concept of Hot and Cold

3.3.1 Hotness and coldness3.3.2 Transfer of Heat

3.4 Light: An Introduction3.4.1 Reflection of light3.4.2 Interaction of light with matter3.4.3 Formation of Images

3.5 Let Us Sum Up3.6 Answers to Check Your Progress3.7 Glossary3.8 References

3.1 INTRODUCTION

Teaching of science at school level must be related to experiences in day-to-day life. There are multiple ways of presenting a concept of science in aclassroom. In this unit an attempt has been taken to explain strategies ofteaching heat, temperature, light and its characteristics. Involving childrenin teaching learning process is quite challenging. Hence, the teacher shouldbe quite resourceful in engaging children in the process of learning. Thisunit focuses on some fundamental concepts of science and its teachinglearning strategies at elementary school level.

3.2 OBJECTIVES

After reading this unit, you will be able to :� explain the concept of heat, temperature and light in the classroom.� differentiate between heat and temperature with simple examples.� prepare children to develop scientific concept on heat, temperature and

light.� describe the properties of light and its significance

3.3 CONCEPT OF HOT AND COLD

Activity -1 (Demonstration by teacherfollowed by group activity)Let us take two beakers as 'A' and 'B'. Asshown in the Fig.3. 1, half of beaker 'A' is filledwith cold water and beaker 'B' with hot water.One child from the class may be asked to dipone hand in beaker 'A' and other hand in beaker'B'. Let the child be allowed to express his

Beaker 'A'(cold water)

Fig.3. 1: Beaker A & B containingcold and hot water respectively

Beaker 'B'(hot water)

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Energy (Heat & Light)feeling/experience in doing this task. Let us hear from the child about hisfeeling in left hand and right hand. The same activity may be repeated withanother child

You are expected to summarize the events in a tabular form on theblackboard with the help of children.

For exampleHot substance Cold substance

Group 1 ________ ________Group 2 ________ ________Group 3 ________ ________Group 4 ________ ________Group 5 ________ ________

Discuss and interact with children about the items recorded in the abovetable. This will help children to list large number of hot and cold substancesfrom their own experiences.

Activity 2 (Demonstrated byTeacher)Let us take three beakers andlabel them as 'A', 'B' and 'C' asshown in Fig.3. 2. We may takecold water in A, normal water inB and hot water in C.i) Call one child from the class

and ask him to dip one handin A and other hand in B.Record the experience/feeling of the child on the blackboard.

ii) Call another child and ask him to dip one hand in A and another handin C, Record the experience/feeling of the child on the blackboard.

iii) Call another child and ask him to dip one hand in B and other hand inC. Record the experience/feeling of the child on the blackboard.

The responses of three children should be noted on the blackboardsystematically in a tabular form. e.g.:

A B C

Child 1

Child 2

Child 3

Beaker 'A'(Cold Water)

Beaker 'B'(Normal Water)

Beaker 'C'(Hot Water)

Fig. 3.2 : Beaker A, B & C with water atthree different temperatures

26

Scientific Concepts Summarize the recorded observations to make the children understand theconcept of hot and cold on discussion and interaction with children. Let usanalyze the table critically to help children to develop clarity in understandingthe concept of hot and cold.

3.3.1 Hotness and coldnessActivity 3 (Demonstrated by teacher)

Let us take some hot water in A,normal water in B and a mixtureof hot and normal water in C, asshown in Fig 3.3

i) Call one child from the classand ask to dip one hand in Aand other hand in B. Recordthe experience/feeling of thechild on the blackboard

ii) Call another child and askto dip one hand in A and other hand in C, record the experience/feelingof child on the blackboard

iii) Call another child and ask to dip one hand in B and other in C, recordthe experience/feeling of the child on the blackboard.

Summarize the recorded observations to make the children understand theconcept of hot and cold and the concept of hotness and coldness as well, ondiscussion and interaction with children. Blackboard must be usedsystematically to present the answers of children. Analysis of the recordedfacts can develop scientific enquiry and power of understanding of childrenon the concept of hotness and coldness.

Beaker Ahold water

Beaker CMixture of hotand cold water

Beaker B

Fig. 3.3 : Beaker A, B & C with water at threedifferent temperatures

On the basis of conclusion, we can say that degree of hotness of A, B, Cdifferent from one another. Hotness of an object is called temperature.For measuring the hotness, we need an instrument called Thermometer.Showing a thermometer teacher is expected to explain its different partand its use.Using the thermometer, demonstrate the measurement of temperature inbeaker A, B, & C. and explain children the measure of hotness in A, B,and C .This exercise can be performed in groups. Teacher can facilitate inanalyzing results of different groups. This will facilitate children inhandling scientific apparatus and conducting experiments.

27

Energy (Heat & Light)3.3.2 Transfer of heat

Activity 4: (To be demonstrated by teacher)

Let us take twotroughs as shown inFig. 3.4 and labelthem as 'A' and 'B'.Fill three-fourth oftrough 'A' with hotboiled water(troughs may beplaced on a tripodstand and a Bunsenburner may beplaced below thetrough A to boilwater. Once thewater starts boilingremove the burner) and fill three-fourth of B with cold water. Insertthermometer in trough 'A' and another in trough 'B'. Thermometer may befixed through clamp stands as shown in the figure.

Time Temp of Beaker 'A' Temp of Beaker 'A'1 Min2 Min3 Min4 Min5 Min6 Min

Temperature of troughs A & B be noted separately with the help of children.Prepare a table and ask children to note the temperature, at an interval ofone minute. Teacher is expected to note the temperature of A and B on theblackboard as per the following table

Summarize the recorded observations on discussion and interaction withchildren. Discussion should include decrease in trend of temperature in Aand increase in temperature of B. Teacher is expected to develop questioningability /enquiry ability of children through discussion and interaction withchildren.

ObservationTemperature of Beaker 'A' : __________Temperature of Beaker 'B' : __________

Beaker Aboiled water

Beaker Bcold water

Fig. 3.4: Beakers A & B with hot and cold water respectively

Discuss and interact with children on the basis of following lines:1. What do you find over a period of 6 mins in beaker A?2. Why temperature of beaker 'A' decreases gradually?3. What do you find over a period of 6 mins in beaker A?

28

Scientific Concepts 4. Why temperature of beaker 'B' increases gradually?5. From this what conclusion can be drawn?

Heat is transferred from beaker A (hotter end) to beaker B (colder end).

The process of transfer of heat from hotter end to colder end is calledconduction

There is an U-shaped iron rod used in this experiment.What is the use of the metallic connector from A to B ?

Substance which helps in conduction of heat from hotter to colder endis called conductors



1. Name some objects from real life, which conduct heat.

Instead of iron rod what else can be used? Let us discuss this question withchildren.

Activity 5Repeat the same experiment (Activity 4) using a U-shaped 'wooden'connector from A and B instead of a metallic rod. Discuss and interact withchildren about their observation and experience and help them to drawconclusion from the experiment, like we have done in Activity 4.

A substance which cannot conduct heat from hotter end to colder end iscalled insulators.

Heat can not be conducted form one body to another body through wood.Is there any other substance like wood through which heat can not beconducted?

29

Energy (Heat & Light)

Activity 6Let us take a beaker containing three-fourth ofit with water as shown in Fig 3.5 .Insert twothermometers as shown in figure. Onethermometer 'A'is dipped up to the lowersurface and other is just dipped at the upperlevel.

The beaker may be heated with Bunsen burner/spirit lamp and note the reading ofthermometer 'A' and 'B' separately, after adefinite time interval in a tabular form.

Time Temp of Beaker 'A' Temp of Beaker 'A'1 Min2 Min3 Min4 Min5 Min6 Min

Summarize the recorded observations with the discussion and interactionwith children. Analyse in detail about the rate of rise in temperature in Aand B. Ask children to find the difference in rate of rise of temperature in Aand B and state their observations. Children may be asked to give theirobservations in group. Teacher is expected to analyse the observations ofeach group and summarise them as follows:

Observation� Temperature noted through two thermometers is different at each time.� Gradually there is increase in temperature of both thermometer A and B.� Always temperature noted through thermometer A is higher than that of

thermometer B.



1. Name some objects from your real life experience, which do not conduct heat.

Fig. 3.5: Water being heated in abeaker with two thermometers toshow difference of temperature attwo different levels

30

Scientific Concepts On the basis of the above observations each group may be asked to answerthe following questions:

Could you compare the temperature of water at lower part of the beakerwith that of water at upper part of beaker?

Could we say heat is transferred from bottom of the beaker to top of thebeaker?From this what conclusion can be drawn?

Similarly transfer of heat from hotter end to colder end and through gas(air) can also be demonstrated by lighting a candle.

Process of transfer of heat from hotter end to colder end through liquid iscalled convection

On the basis of discussion with children ask them to prepare a list ofexamples to explain the phenomenon of convection from their experiences

1.2.

For conduction and convection there is the need of a medium, Solidin case of conduction and liquid in case of convection



1. Windows of the houses in coastal areas are generally made to face the sea. Give reason

Transfer of heat without any mediumIs it possible for the transfer of heat from one end to another end withoutany medium?

Activity 7Let us explain to children the use of a room heater/ fire in a container.We may ask children why we use room heater/fire in a container.What do we generally feel when we on the switch of room heater?Then explain children why do you feel so?

31

Energy (Heat & Light)Answers of each question should be followed by discussion and interactionwith other children

Activity 8Let us take a utensil and heat the same with a Bunsen burner/spirit lampand place it at the centre of a room. We may ask children to take their handsnear the utensil (without touching).

What do they feel?Why do they feel so?After some time (about 15 min.) ask children to touch the utensil.What do you feel?Why does the utensil become cold?Discuss and interact with children about the process and help them tounderstand how conduction of heat takes place without medium.

The process of transfer of heat without any medium is called radiation

Could you give some more example of radiation related to the phenomenonof real life situation?



1. Generally people use umbrella with black color cloth when they go out. Give reasons.

3.4 LIGHT: AN INTRODUCTION

3.4.1 Reflection of light

Activity 9Let us take a beaker and fill three-fourth of it with water. The beaker maybe kept on a table without any disturbance. Ask one or two child to look intothe water from the top (upper face) of the beaker.

What do you see?Teacher is expected to write the answers of children on the blackboard.Discuss and interact with children how they are able to see their face throughthe surface of water. And then ask could you give some more example ofobject through which you can see your own face?

1. Shining stainless utensils

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Scientific Concepts 2. Stem plate

Your face that is visible through surface of water, polished/shining surfaceis called image

Activity 10 (To be demonstrated by teacher)Let us take a mirror and place it on atable as shown inthe Fig 3. 6. In front of the mirror (atcertain distance from the mirror) place an object.Let us ask children one by one to observethe object and the mirror carefully.What do you see through the mirror?Do you find any thing inside the mirror?

Fig. 3.6: Reflection of an object in amirror

Source: NCERT 2009: Science Textbook for class VII

The same object appear inside the mirror is called image of the object.

Could you compare the distance of the object from the mirror with thedistance of the image from the mirror?

Distance of the object from the mirror is equal to the distance of theimage from the mirror.

Activity 11 (To be performed in group)Perform the experiment taking a chessboardas shown in Fig 3.7 and have discussion andinteraction with children about the positionof the object, its size etc.

Children may be asked to see the image ofthe object through the mirror and thendiscuss with them about the size of the imageand its distance from the mirror etc.

Teacher is expected to help children to repeat the experiment with changingthe position of the object on the chess board. Use of chess board will certainlyhelp children to assume object distance and image distance without anymeasurement.

Compare the image of the object with that the object itself, what do youobserve?

Fig. 3.7: Process of reflectionusing chess board and mirror

Source: NCERT 2009: Science Textbook forclass VII

Let us take a pencil and keep it in front of the mirror and observe its image.

� Name the object _______________

Image of the object formed through the polished surface (mirror) is exactlysame as that of the object

33

Energy (Heat & Light)� Name the image _______________

� Compare the size of theObject with that of the image _______________

Let us ask one child to take the object very near to the mirror slowly. 'Observethe movement of image' and its position.

Ask another child to take the object 2 cm nearer to the mirror slowly andobserve the movement of image and its position.

Ask another child to take the object 5 cm away from the mirror slowly andobserve the movement of image.

Summarize the whole activity with discussion and interaction with childrento make the child realize that size of the object = size of the image when theobject is placed in front of a plane mirror. At the same time distance of theobject from the mirror = distance of the image from the mirror.

3.4.2 Interaction of light with matter

Activity 12 (To be demonstrated by teacher)At the center of a darkroom, let us place a table,keep a beaker on it. Three-fourth of the beakermay be filled with water. Let us keep the beakerundisturbed on the table. Cover the beaker withan opaque object (cardboard) with a small holeat the centre. From the upper surface, allow light(from a torch) to fall on the through the hole atan angle as shown in the Fig 3.8. Children areadvised to observe at the ceiling of the room.

Teacher may discuss with children in asking questions like what do they seeon the ceiling? Observations of different child may be noted on theblackboard.

Repeat the activity by allowing the light to fall at different angles on theupper surface of water and ask children to observe the image formed on theceiling of the room.

Activity 13Let us fix a mirror on the wall of dark room. Repeat the above activity byallowing the light through a torch to fall at different places on a mirrorfixed at the wall. Teacher is expected to ask children one by one what dothey observe on the opposite wall of the room?

Explain to the children the process and help them to draw any conclusionfrom their observation. Teacher can repeat the same experiment by focusinglight through a torch on the opaque wall and ask children to draw their

Fig. 3.8: Reflection of lightthrough an opaque object

34

Scientific Concepts observations. Now teacher is expected to discuss children to compare twosets of observations from two different experiments, to make childrenunderstand the concept of interaction of light with matter.

On the basis of the Activity 12 and 13, one can explain how the direction oflight changes when allowed to fall on a polished surface. We can say thatthe change in direction of light by a plane polished surface is called reflection

On the basis of discussion with children ask them to give some otherexamples of reflection of light from their experiences.1.2.

3.4.3 Formation of Images: Plane Mirror

Activity 14 (To be demonstrated by teacher)``Let us take a candle and a plane mirror. Perform the experiment placingthe candle at different position in frontof the mirror as shown in Fig.3.9 andask children to see its image atdifferent distance from the mirror.It is important to note thecharacteristics of the images formedwhen the object is placed at differentpositions in front of the mirror.

On the basis of discussion and interaction with children, write theirobservations on the black board.

When light falls on a polished surface, the surface changes the directionof light. This is due to interaction of light with matter

Fig. 3.9: Process of reflection


1. Size of the candle is equal to its image.2. Flame of the candle is appearing on the top and flame of image also

appears on top.3. Distance of the candle from the mirror is equal to distance of its

image from the mirrorSuch image is said to be erect and virtual.

Observations1. Size of the candle is equal to its image.2. Flame of the candle is appearing on the top and flame in the image

also appears on the top.3. Distance of the candle from the mirror is equal to distance of the image

from the mirror. (Such image is said to be erect)

35

Energy (Heat & Light)Activity 15Let us ask one child from the class to stand in front of a plane mirror byraising his right arm and observe the image formed through the plane mirror

Teacher is expected to discuss with children on the basis of followingquestions:

1. Which hand of Object (object is the child) has been raised (left/right)2. Which hand of the image has been raised (left/ right)

Let us ask the child to hold his left ear and see the image and collectobservations about change in sides on the basis of discussion and interactionwith children.

The same experiment can be repeated with two/three other children.Discuss and interact with children about the object and the images formedat different instances.Let us facilitate the children to summarie the result in groups and note theirresponses on the blackboard and then generalize on the basis of analysis.

In a plane mirror sides of image appears to be interchanged i.e. left appearsright and vice-versa.



1. Give an example of the phenomenon of interchange of side used in our day-today-life.

Formation of image through Spherical mirror

Activity 16Let us take a bright, polished spoon and ask a child to see his face throughthe outer side of steel spoon as shown inthe Fig 3.10 and ask – Could you see yourimage?

Now taking a pen in front of outer surfaceof steel a spoon ask a child Do you get theimage of the pen through the spoon ?

Repeat the activity using the inner surfaceof the steel spoon and ask to observe theimages.

Fig. 3.10 : Reflection throughspherical surface


36

Scientific Concepts

The outer surface of a polished spoon called convex surface i.e. the reflectingsurface is convex. (Teacher is expected to demonstrate the same with aconvex mirror)The inner surface of a polished spoon called concave surface i.e. thereflecting surface is concave. (Teacher is expected to demonstrate the samewith a concave mirror)

The curve of shining/polished surface of a spoon acts as a mirror calledcurved mirror/spherical mirror. Teacher may show some concave andconvex mirrors to children to help them to understand the concept



1. Note the characteristics of image through a convex surface (using outer surface of spoon)(i)(ii)(iii)

Formation of images by lenses

Let us get some lenses and ask childrento touch and feel them. Taking somespectacles we can ask children to touchand feel the glass used in them.

Let us show a convex lens to childrenand ask them to examine it with regardto its shape, size etc.

Lenses that are thickest at the middlethan edges are called convex lens.Teacher can demonstrate the same

Fig. 3.11 : Image formation throughconverging and diverging lenses

Lenses that are thicker at the edge than the middle are called concave lens.Teacher can demonstrate the same using a convex lens

All lenses are transparent and light can pass through it.

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Energy (Heat & Light)Activity 17Let us take a convex lens and a glass and keep it on the table. Cover theglass with a cardboard and make two small holes. Let us allow light to fallon it. A white drawing sheet may be kept on the opposite side of the lensand adjust its portion to get a bright spot on it.

ObservationReflection of light after falling on the convex lens bends inwards. i.e.converges towards each other. (The lens is called converging lens) nowchange the position of torch and accordingly adjust the position of drawingsheet to get the sharp image.



1. Perform the similar activity (Activity 17) taking a concave lens and state your observation on the characteristics of image formed.

LET US SUM UP

In this unit, you learnt:

� Teaching strategies for concepts of heat, temperature, heat transfer.

� Concept of light and its interactivity with matter

� Presenting the above concepts through several examples andclassroom activities that are learner-centric.

ANSWERS TO CHECK YOUR PROGRESS

Answer 11. i) steel and silver spoon,

ii) key of a lock,iii) a piece of iron rod,iv) water etc.

Answer 21. i) Plastic scale, ii) plastic comb, iii) wood piece, etc

Answer 31. Air present above the sea level is generally cold. Land mass air is getting

heated up quick and goes up. To fill the gap cold air from above thelevel of sea blows towards the land (by the process of convection).Therefore to get the cold air the windows are generally made to facetowards sea.

38

Scientific Concepts Answer 41. Good absorbers are good radiators. Black color cloth used in a umbrella

absorb heat from the sun and radiate the same back to the atmosphere(by the process of radiation) at the same rate. So we feel little comfortin using umbrella having a black cloth.

Answer 51. The word AMBULANCE is generally written in the laterally inverted

form in front of a vehicle. It is because the driver of a vehicle ahead ofan ambulance looks through the mirror and can read it as'AMBULANCE' (It is because of the phenomenon of lateral inversion.)and can allow the ambulance to pass.

Answer 61. i) Image always formed at a point,

ii) image may be real or virtual,iii) image is not magnified

Answer 71. Readers are expected to give their own comment. however the common

observations are; i) point image is formed, ii) Image is virtual, etc

GLOSSARY

Conduction Transfer of heat from the hotter end to the colderend of a body

Conductors Substances which help in heat transfer from hotterto colder end of the body, e.g. metals

Insulators Substances which cannot conduct heat from hotterto colder end of a body, e.g. wood, rubber

Convection The process of heat transfer from a hotter to colderend in a liquid

Radiation The process of heat transfer in the absence of anyMedium

REFERENCES

Agrawal, O. P. (1999) IIT Chemistry, Jai Prakash Nath Publication, Meerut,Uttar Pradesh

Kumar, N. (1998) Comprehensive Physics, Laxmi Publication, New Delhi

Nanda, R. N., et.al; (1997) Textbook of Modern Chemistry, KalyaniPublication, Ludhiana, Punjab

39

Energy (Heat & Light)NCERT (2008) Science Textbook for Class VIII; National Council ofEducation Research and Training, New Delhi

NCERT (2009) Science Textbook for Class VII; National Council ofEducation Research and Training, New Delhi

Sharma, K. N. (1999) ISC Physics, Kalyani Publication, Ludhiana, Punjab

40

Scientific Concepts UNIT4 PLANT CELL AND ANIMALCELL

Structure

4.1 Introduction4.2 Objectives4.3 Cell Structure

4.3.1 Comparison of Plant Cell and Animal Cell4.4 Size of Cell4.5 Let Us Sum Up4.6 Answers to Check Your Progress4.7 Glossary4.8 References

4.1 INTRODUCTION

It is important to understand about the basic functional unit of an organ in aliving organism called the cell. Robert Hooke in 1665 observed the smallstructures from cork sections under simple microscope which looked likebee hive (honey comb). He called them cell (Greek Kytore = cell, latin cella- hollow space). Cell was discovered in this way. Living beings are classifiedas plants and animals. Developed animals have definite size and shape whileplants have both different size and shape. In this unit you will learn the conceptof cell, its structure and differences between plant and animal cell.

4.2 OBJECTIVES

After reading this unit you will be able to:-� Define a cell� Explain the structure of a cell� Prepare simple slide of onion peel� Observe the structure of onion cells under a microscope.� Differentiate between plant and animal cell.� Illustrate with examples the differences in shapes and size of cells

4.3 CELL STRUCTURE

Activity 1With the help of a microscope, observe the onion peel or cauliflower leafpeel. You will see the cells and basiccomponents very clearly. You have tojust place a small piece of a thin onionpeel in a drop of water on a glass slideand observe under the microscope.You can add a drop of methylene bluealso. Fig 4.1 : Structure of Onion Peel

41

Plant Cell and Animal CellActivity 2Collect a honey comb from a tree or abuilding when the honey bee's box is orcompartments as they were seen in the corkslice.

Cells in the living organisms are complexliving structures unlike non-living bricks.There are millions of living organisms. Theyare of different shapes and sizes. Theirorgans also vary in shape, size and number of cells. Even a single celledorganism like amoeba, performs all the necessary functions that multicellularorganism performs.

The microscopic structural, fundamental and functional unit of living beingsis called cell. Structural and functional unit means its proper functioning ofbody so that the organism can lead its life successfully. Cells of livingorganism could be observed only after the discovery of a improvedmicroscope. Have you seen a building? Both, bricks in a building and cellsin the living organism are basic structural units. The building though builtof similar bricks, have different designs, shapes and sizes. Similarly, in theliving world, organisms differ from one and another but they all are madeup of the basic structural unit - the cell.

There is a walled-like structure surrounding all the living and non-livingsubstances called the cell wall or cell membrane. The living substancesurrounded by all wall is called protoplasm. Protoplasm is a colourless,semi-transparent, semi-liquid colloidal complex compound in which otherimportant structures of the cell are present. Protoplasm is made up of bythe combination of cytoplasm and the nucleus. Nucleus is the control centreof the activities of the cell.

The part of protoplasm which is found between the cell wall and the nucleusis called cytoplasm. The liquid inside the nucleus is called as nucleoplasm.Cytoplasm is a jelly like thick liquid in which various important structureslike (components or organelles) nucleus, chloroplasts, mitochondria,ribosomes, golgi bodies, endoplasmic reticulum, centriole, vacuoles andmany non-living substances are found.

4.3.1 Comparison of Plant Cell and Animal Cell

Activity 3For example, look at the Diagrams A and B. You will see that the shape ofone is hexagonal and the other one is nearly circular. If we discuss aboutthe basic structures of both you will find some similarities as well as somedifferences also.

Brick Wall

42

Scientific Concepts

DIAGRAM A (Plant Cell)

DIAGARAM B (Animal Cell)



1. Write down the points, which show the difference in diagram A and B

There are three parts in a typical cell :-(i) Cell surface(ii) Cytoplasm(iii) Nucleus

43

Plant Cell and Animal CellThe cell surface includes cell wall and the cell membrane. Animal cells donot have a cell wall. Instead a plasma membrane is there, which surroundsthe cytoplasm from all four sides. Animal cells are of various shapes, whichdepends on structures of specific animals. Cells are rectangular, sphericalelongated and round in shape. Choloroplasts are not found in animal cells,likewise vacuoles are minute or in less quantity or absent also. Centriolesare found (see diagram B) in the cytoplasm with stored food in the form ofglycogen. Some other essential organelles are also found in cells.

In addition to all membrane there is an outer thick layer in cells of plantscalled cell wall. This additional layer surrounding the cell membrane isrequired by plants for protection against variations in temperature, highwind speed, atmospheric moisture etc.

Chloroplasts are present but no centrioles are present in a plant cell. Thestored food is present in the form of starch in the plant cell. Other organelleslike nucleus, cytoplasm, mitochondria, golgi bodies, endoplasmic reticulumare present. Vacuoles are large in shape and size. (see diagram A)



1. Write the difference between plant cell and animal cell.

4.4 SIZE OF CELL

The size of cells in living organisms may be small as a millionth of a metreor may be as large as a few centimeters.

However, most of the cells are microscopic in size and are not visible to theunaided eye. They need to be enlarged or magnified by a microscope.

The smallest cell is 0.1 to 0.5 micrometre in bacteria. The largest cellmeasuring 170 mm x 130 mm is the egg of an ostrich. The egg representsa single cell and is big enough to be seen by the unaided eye.

The size of the cell has no relation with the size of the body of the animal orplant.

It is not necessary that the cells in the elephant be much bigger than thosein the rat. The size of the cell is related to its functions. For example nervecells, both in the elephant and rat, are long and branched. They perform thesame function that of transferring messages.

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Scientific Concepts 4.5 LET US SUM UP

After reading this unit you learned that� The smallest living part of an organism is the 'Cell'.� Cells exist in different shapes and sizes.� Number of cells varies in all organisms.� Animal cells do not have cell wall, chloroplasts and big central vacuoles,

which are present in plant cells.� All cells have three main parts: (i) cell membrane, (ii) cytoplasm, which

contains the organelles and (ii) the nucleus.


Answer 11.(a) In diagram A cell wall and plasma membrane are seen but in

diagram B cell wall is not there.(b) In diagram A big vacuoles are seen but in diagram B they are

very small or absent.(c) Chloroplasts are there in diagram A and absent in diagram B(d) No centrioles in diagram A but present in diagram B.

Answer 21. Write down the difference between plant and animal cell.

S. Points Plant Cell Animal CellNo.1 Cell wall Present Absent

2 Vacuoles Small or large are present Very small or absent

3 Chloroplasts Present in cytoplasm Absent

4 Centrioles Absent Present

4.7 GLOSSARY

Cell The basic structural and functional unit in a livingorganism

Cell Membrane The boundary which encloses the cytoplasm and nucleusof the cell

Cell Wall The outer thick layer in addition to the cell membranein plant cell

Protoplasm The colourless semi transparent colloidal substancefound in the cell

Cytoplasm The protoplasm found between the nucleus and cellmembrane.

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Plant Cell and Animal CellNucleus The central dense round body in the centre of the cellwhich controls the functions of the cell.

Chloroplast The green coloured plastids found in the cytoplasm ofleaf cells

4.8 REFERENCES

High School Science, Part -3

Intermediate Botany

Intermediate Zoology

46

Scientific Concepts UNIT 5 ENVIRONMENT

Structure

5.1 Introduction5.2 Objectives5.3 Concept of Environmental Pollution

5.3.1 Air Pollution5.3.2 Water Pollution5.3.3 Land Pollution

5.4 Acid Rain5.4.1 Causes of Acid Rain5.4.2 Effect of Acid Rain,5.4.3 Preventive Measures

5.5 Ozone Layer Depletion5.5.1 Causes of Ozone Layer Depletion5.5.2 Effects of ozone depletion

5.6 Green-House Effect5.6.1 Green-House Gases

5.7 Global Warming5.7.1 Effects of Global Warming5.7.2 Control of Green House Gases and Global Warming

5.8 Efforts Made to Conserve and Improve Environment5.8.1 International level5.8.2 National level5.8.3 Individual and community level

5.9 Natural Calamities5.9.1 Floods5.9.2 Cyclones5.9.3 Droughts5.9.4 Earthquakes

5.10 Let us Sum Up5.11 Answers to Check Your Progress5.12 Glossary5.13 References

5.1 INTRODUCTION

Nature's beauty Polluting environment

47

EnvironmentThis unit describes the meaning, causes, effects and preventive measuresrelated to current environmental issues like acid rain, global warming etc.The activities, topics for bulletin board are aimed to sensitize the studentsto environmental concerns and inspire them to explore further. This unitwill help you to explain different environmental issues to your studentsaccording to their level of comprehension, analytical ability, language skillsand knowledge of other related subjects. We have devoted one sectiontowards discussion of natural calamities.

5.2 OBJECTIVES

After going through this unit you will be able to

� explain concept of environmental pollution, types of pollution, acidrain, causes and effects of acid rain and their control with relatedactivities.

� describe ozone layer depletion, effects of depletion and controlmeasures.

� describe greenhouse effect and global warming, their causes, effectsand preventive measures.

� discuss methods of environment protection in communities.� identify and perform activities for environment protection campaign

in schools and communities.

5.3 ENVIRONMENTAL POLLUTION:

Have you seen a Traffic Policeman at a crossing wearing mask? Whathappens when a fire in chulla extinguishes? What is the scene at a busyroad? All the three incidents indicate the emission of smoke fromautomobiles and chullas etc. How will you feel if you are forced to breathein such atmosphere?

It is the addition of any undesirable substance to air, water and soil eitherby natural process or human action which affects the quality of environment.Depending upon the type of environment its pollution is generally of threetypes.

I Air PollutionII Water PollutionIII Land Pollution

5.3.1 Air Pollution is the addition of undesired substances in air by humanactivity or by natural means that are harmful to human existence. Givenbelow are the examples.a) Natural Resources like volcanic eruption, forest fire and decay of

organic matter. The toxic gases are released.b) Human activities like burning of coal, combustion of oil, smoke from

industries and stone crushers. Toxic gases and other pollutants arereleased in the atmosphere.

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Scientific Concepts Effects of Air Pollution1. Particulate matter like soot dust, cause irritation of respiratory tract

and diseases like asthma.2. Cotton dust from industries causes lung fibrosis.3. CO2 is a green house gas and causes greenhouse effect.4. Carbon Monoxide causes laziness, exhaustion5. Sulphur dioxide causes acid rain.6. Emission of chlorofluorocarbons causes Ozone layer depletion.

Activity 1Collect leaves of some plant from polluted area (e.g. busy road) and fromclean area (garden). Wash the samples separately in bowl of water. Thecolour of water is dark in leaves from polluted area due to mud on the leafsurface. Compare the length and breadth of leaves. Let us discuss someeffects of pollution in detail.

5.3.2 WaterPollution

You might have observed the bad smell, impurities, and change in colourin your drinking water. The rivers Ganga and Yamuna are being used forpouring industrial and other wastes. The results are alarming. The recentnews of pollution of Budha Nullah in Punjab depicted clear indications ofincrease in mineral content of ground water resulting in diseases like cancer,arthritis flourisis, and paralysis.

Definition: It is the degradation of quality of water due to addition ofsubstances, chemicals that makes it unfit for human use.

Activity 2 for Teacher1. Arrange a visit of students to a nearby water treatment plant and

discuss some more purification methods and modern methods to getpure drinking water

2. Organize a debate on impacts of sewerage system.

5.3.3 Land pollution: The change in physical, chemical and biologicalproperties of soil due to addition or removal of substances which reduce itsproductivity.

5.4 ACID RAIN

My mother always abides me to take bath in first rain. We feel watery eyesand itching sensation in metro cities. It was shocking to read the newsabout red rain in Kerala and Yellow rain in Mainpuri in U.P. The details ofnews indicated at industries were set up near the residential areas and thechemicals from the industries got released in the atmosphere for which therain became colored.

49

Environment5.4.1 Caused of Acid Rain

As the name suggests it is acidicrain because several chemicalindustries produce oxides ofsulphur and nitrogen. In airsulphur dioxide and nitrogen oxide(NO

2) combine with water to form

sulphurus acid and nitrous acidwhich come down with rain water.Sources of SO

2 are industrial fuel

and smoke.

When acids dissolved in water fall down in the form of rain drops, it iscalled acid rain. The pH of rain water is below 5.7.

5.4.2 Effects of Acid Rain

It damages the quality of soil and water and plants on earth, destroys fruitsand vegetables and oxygen content of water, and causes discoloration anddeterioration of buildings. The threat to Taj Mahal in Agra from the toxicgas sulphur-di-oxide emission from Mathura Refinery is a live example ofthe effect of Acid Rain.

5.4.3 Preventive Measures

Following measures should be taken to prevent acid rain

1. Wet scrubbers to separate the toxic gases should be used.

2. Factories should be located away from historical monuments andresidential areas.

Activity 3Ask the students to observe the effects of first rain in their homesThe dirty floors, roofs etc. get cleaned itself due to the acidic nature ofrain. Do they also observe such kind of effect?

The industrial city of Kanpur releases lots of wastes in air and waterOrganize a debate in class on causes and effects of such wastes

Activity 4Organize a visit to industry and observe if any preventive measures aretaken to control the pollutants. Hold a group discussion and find out whatsteps can be taken to prevent the emission of harmful gases. Make aquestionnaire with following questions

i) What is produced in the industries?

Fig. 5.4.1 : Diagrammatic representation ofAcid Rain

50

Scientific Concepts ii) How far is the industry from the residential area?iii) What types of wastes are generated?iv) Do they use filters?v) Are the chimneys situated at considerable height

Activity 5Ask the students to collect the rain water in their locality .With the help ofpH paper observe the pH of that water and record the results .Discuss withthe students.



1. Name the following (Figures in the brackets indicate the num-ber of letters)

i. Industrial gas causing acid rain (14)ii. Gas combines with water to form HNO3 (15)iii. Refinery emitting SO2 (7)iv. In acid rain pH decreases/increases (9)v. Monument damaged due to acid rain (8).

5.5 OZONE LAYER DEPLETION

Let us list some of the things used to protect ourselves from adverse weatherconditions, e.g. a house, clothes are worn to protect the body from excessheat and cold, using an umbrella or rain coat during rainy season etc. Ourearth also has a protective covering.

The atmosphere is a transparent, colorless, gaseous covering, around theearth. It is divisible into different layers. These are troposphere, stratosphere,mesosphere, thermosphere and exosphere. One of them is stratosphere. This

51

Environmentlayer of earth is present from 10-45 kms above the equator. Stratospherehas a blanket of ozone layer to protect the earth's life from harmful radiationsof sun.

This layer of ozone is also called as Ozonosphere. Maximum concentrationof ozone is at the height of 23-25kmsfrom the earth over equator and 11-16kms over the poles. Ozone has warming effect due to absorption of UVrays and conversion of their energy into heat.

How will the life be if the ozone layer gets removed from the stratosphere?All the radiations will directly come on earth including ultraviolet radiations.

Destruction of ozone is,Destruction of life zone.

Depletion destroys the life,Health, skin and eyes.

The above mentioned lines clearly indicate the importance of ozone layer.Ozone is the form of oxygen made up of three atoms of oxygen. It isnaturally present in stratosphere.

Definition: Thinning of Ozone layer in stratosphere is called ozonedepletion.

5.5.1 Causes of Ozone Layer Depletion

Ozone depletion is caused by pollutants like CFCs (Chlorofluoro carbons),chlorine, nitrogen oxides, carbon tetrachloride and chloroform, etc.

1. CFC: These are compounds of carbon with chlorine and fluorine whichare mainly responsible for ozone layer depletion. CFCs are used inrefrigerators, air conditioners, jets, etc. They are added in atmospheredue to leakage or disposal of old products.

2. CCl4 (Carbon Tetrachloride): It is used as a liquid base in deodorantand room freshener. It is highly stable, i.e. it does not react anddissociate easily. It goes up in the atmosphere and combines withozone and splits it into O2 and O.

3. UV (Ultra-Violet) radiations: UV rays break them down intochlorine, fluorine and carbon. Chlorine breaks ozone into oxygen.One chlorine atom is capable of breaking thousands of ozone molecules.

4. Nitrogen Oxide: Nitrogen oxide is emitted (released) from jet planes,industries, nitrogen rich fuels, livestock waste, fertilizers and duringproduction of nylon.

52

Scientific Concepts 5.5.2 Effects of Ozone Layer Depletion

Thinning of ozone allows harmful radiations to reach the earth surface.Excessive exposure to UV radiation is linked to a number of health problemslike skin cancer, cataracts and weakened immune system. .

Ozone HoleDue to the effect of pollutants, Ozone layer thickness is decreasing. Thereis a large hole in the ozone layer. It was found in 1985 by Farman etal overAntartica. A smaller hole also occurs in stratosphere on Arctic region. Withthe approach of summer, ozone concentration begins to build up, till itreaches maximum in winter.

Activity 6List all the gadgets and instruments that use CFC, CCl4 etc in theirformation. Collect information regarding the latest developments amongdifferent countries about the harmful effects of CFCs. Make a comparativeaccount of some traditional and modern instruments. List some moderninstruments which are CFC free.

Activity 7Encourage the students for celebrating ozone day by performing variousactivities like Essay Writing Competition, Slogan Writing and Painting.Also ask them to list some more important days celebrated as a matter toprotect our environment and earth. Also try to let them find out their purposeof celebration.

Activity 8Organize painting competition on ozone depletion in class to createawareness among students. A slogan competition can also be organized topromote and motivate the students to reduce emission of CFC like pollutants.



1. Write the full form of CFC.__________________________________________________

2. Choose the correct answer:(i) Ozone layer is destroyed due to(a) CFC (b) NH

3(c) SO2 (d) H2O

(ii) Depletion of ozone layer will affect(a) Photosynthesis (b) Buildings (c) Fishes (d) Respiration

(iii) Ozone depletion will result in penetration of(a) UV rays (b) Infrared rays (c) Microwaves (d) Radio waves

(iv) Skin cancer is caused due to(a) UV (b) Infrared rays (c) Visible light (d) Radiowaves

53

Environment5.6 GREENHOUSE EFFECT

Whenever I visit Mumbai in winters, I need less woolen clothes than at mynative village. The glassy building and emission from industries makes thesurrounding warm.

Various ecological problems like environmental pollution, deforestation,energy crises have badly affected the healthy face of world. The result iswarming of earths, atmosphere. It is a problem of global concern and is thebiggest issue of 21st century.

A Greenhouse

A greenhouseGreenhouse - A house made from glass or poly fibre sheet that absorbs thevisible light and infrared rays and prevents them to go back to theatomosphere is called greenhouse. Such houses are made in cold countriesand hilly areas where the average temperature is very low. These housesare used to grow such plants which require high temperature and humidity.

Concept of Greenhouse EffectThe solar radiations are composed of different wavelengths. Earth surfacereceives solar radiations which consist of Ultra Violet, visible rays andInfrared rays. Most of ultraviolet (UV) rays are absorbed by the ozonelayer. Therefore, they are not able to reach the earth's atmosphere. Infrared rays are absorbed by water vapors and CO2 present in the air. Visibleradiations come to earth. The infrared radiations have heating effect due tohigh wavelength. The visible radiations are also blocked due to highconcentration of some gases and water vapors. Due to absorption, theinfrared are redirected back to earth in all directions resulting in warmingof earth's surface and the atmosphere. The green house gases form a blanketover the earth. They control the escape of heat from earth's surface.

Definition of Greenhouse GasesDue to Greenhouse Gases (CO2, CH4, CO) the earth's surface is keptwarm and this phenomenon is called Greenhouse Effect.

54

Scientific Concepts 5.6.1 Greenhouse Gases

CO2 and certain other gases like methane (CH

4), Nitrous oxide and CFC

responsible for greenhouse effect are called greenhouse gases. Concentrationof these gases has increased in the atmosphere and they prevent the solarradiation to go back.

They are transparent solar radiations but retain and partially reflect backlong wave heat radiations. The trend of increase in the concentration ofgreenhouse gases (GHG) since pre-industrial times are described below:

Carbondioxide (CO2):The normal concentration of CO2 is 0.033 % in atmosphere. Theconcentration of CO2 above 0.03% has adverse effect on our climate andliving organisms.

The main sources through which CO2 is released in the atmosphere are -

� Burning of fossil fuels,� Decay and decomposition of dead organisms,� Respiration of living organisms� Forest Fires� Domestic cooking� Automobile exhausts� Thermal Power Plants� Volcanic Eruptions

CO2 is the most abundant (60%) greenhouse gas in the atmosphere.

MethaneIt is produced by incomplete decomposition of organic matter in the absenceof O

2 . The sources of methane are

� Fresh water wetlands� Flooded rice fields� Biomass burning

Methane has global warming potential 63 times to that of CO2

Activity 9Divide the class in two groups. Identify one monitor in each group. Askhim to play the role of Chairman/Mayor of city. Tell him about globalwarming and sources of GHG. Hold a debate in class. Ask them abouttheir style of working and ideas to control this problem.

Activity 10In many districts of Punjab, Haryana and UP, the agricultural scientistsare advising the farmers to shift from paddy cultivation to other crops. Findout the reason behind that.

55

EnvironmentOrganize the students in groups and assign them a project of survey ofpaddy cultivation area in the country and to calculate the amount of methanereleased.

5.7 GLOBAL WARMING

You have already been introduced to the issue of global warming. Let usnow study some of the effects.

5.7.1 Effects of Global Warming:

The global warming caused due to greenhouse gases will affect the weather,sea level, distribution of organisms, food production and fishery resourcesin oceans etc.

1. Effects on Weather and Climate: The global average temperature hasincreased by 0.80C by 2005. Due to increase in temperature - moisturecarrying capacity increases, resulting in warming of troposphere. Andremaining areas will become drier and suffer from greater watershortage problems.

2. Sea Level Rise: Increase in temperature will lead to melting of icefrom polar caps and glaciers. Thermal expansion of oceans will occur.This will cause sea level to rise by 8 inches resulting in flooding oflow lying coastal areas.

3. Effect on distribution of Organisms: Some species will extinct e.g.Coral reefs, some will migrate. Species like weeds, pests will prosper.There will be impact on plants such as early flowering and fruiting ofplants.

4. Effects on Agriculture: Frequency and duration of droughts willincrease. Transportation and respiration rate will increase. Cropproduction will decrease.

5. Human Health: Hot and humid climate will cause respiratory diseases.

5.7.2 Control of GHG and Global Warming

Global Warming can be checked by reducing the concentration of CO2,

CH4 etc. in the atmosphere. Some steps to control global warming are as

follows:

1. CO2 is main greenhouse gas. The amount of CO

2 can be reduced by

plantation (reforestation) of trees

2. Alternate resources of energy should be used in place of fossil fuels.

3. Artificial/Synthetic nitrogen containing fertilizers should be usedminimally.

4. Old refrigerators, ACs should be discarded and properly destroyed.

5. Substitute of CFCs should be developed.

56

Scientific Concepts Activity 11Help the students and involve them in planting trees in your schools. Youcan also encourage them to plant one tree on their birthday and take chargeof its maintenance.

Discuss the importance of Van Mahotsav with them.

Activity 12Ask the students to make an artificial greenhouse at home using poly fibersheet as cover and place plants inside it. Let them record the temperatureand humidity of greenhouse and compare the difference from externalsurroundings.Organize a discussion in the class on their findings.

Activity 13Put up newspaper clippings related to waste accumulation, production ofmethane due to its degradation and its dangers on bulletin board.

Also make a scrap book of these clippings.

5.8 EFFORTS MADE TO CONSERVE AND IMPROVEENVIRONMENT

5.8.1 International Level:

1. UNEP: United Nations Conference on Environment and developmentat Stockholm, June 1972 urged to work towards development inharmony with nature.

2. Montreal Protocol (1987): 27 industrialized countries agreed to limitproduction and consumption of CFC to half the level of 1986.

3. Earth Summit: Rio Declaration in June 1992 at Brazil, insisted oncontrolled development keeping in view the sustainability environment.

4. Antarctic Treaty (1952) Ban on military activity and nuclearexplosion.

5. Kyoto Agreement: The Kyoto Protocol was agreed at the thirdconference of the parties (COP3) in December 1997 in the Japanesecity of Kyoto.

The goal of the Kyoto Protocol was that industrialized countries shouldreduce their greenhouse gas emissions by at least 5% compared to the 1990level, calculated as an average over the period of obligation, 2008 - 2012.The industrialized countries have differing obligations under the KyotoProtocol. The European Union has agreed to reduce greenhouse gasemissions by 8%. The USA agreed to an obligation of 7%, Canada andJapan 6%, Russia and New Zealand may emit the same as in 1990, whereasNorway and Iceland may emit 1% and 10% more respectively.

Apart from CO2, the Kyoto Protocol also includes the five other greenhouse

57

Environmentgases. There are methane, nitrous oxide and the industrial gases HFCs,PFCs and SF6.

5.8.2 National Level:

1. Conversion of public transport vehicle to CNG (Compressed NaturalGas)

2. Environmental Protection Act framed after Bhopal gas tragedy coversaspects for protecting environment.

3. Forest Act: Setting Management and Protection of forests.4. Pollution Act: Central Pollution Control Board enforces rules for

pollution control and plans projects for conservation of environment.

5.8.3 Individual and Community Level:

We can also reduce consumption by -� recycling Waste� saving water, fuel and electricity.� planting more trees� using CNG vehicles� avoiding use of plastic bags.� avoiding throwing of garbage and not to litter at open.� learning about environmental issues through media� avoiding use of spray and deodorants.� changing the instruments using alternatives of CFC

Activity 14Divide class into two groups and discuss about polluted areas in India andprovide reasons for same, other group to find ways to control and reducepollution.

Put the result on the Bulletin Board.

Activity 151. Make a list of themes on world environment day 5, June from 2001-

2008. Analyse and comments on different themes.2. Organise and coordinate eco-clubs and create environment awareness.3. Discuss with students about Montreal protocol (an agreement) to reduce

CFC products by 50% in 1998. Today 175 countries have signedMontreal protocol.

4. Ask students to collect information about Kyoto, Japan Protocol, 1997for mitigating global changes.


b) Compare your answers with those given at the end of the unit.

1. Match the following:i. Global Warming a) Global Warmingii. Green House Gas b) Rise in Temperatureiii. Sea Level Rise c) Methaneiv. Melting of Ice d) Green House Gases

58

Scientific Concepts 5.9 NATURAL CALAMITIES:

� Did you know?

� Worst flood in history - 900,000 dead (Yellow river-China-1887)� Deadliest earthquake-1,100,000dead(Egypt, Syria and the

Mediterranean� Worst drought ever-9,000,000dead(China-1876-1879)� Cyclone hit coastal Orissa in October 1999, killing more than

10,000 people� Earthquake in Gujarat on Jan 26,2001 killing 30,000 people� Tsunami on Dec 26, 2004 near Sumatra killing 300,000 people

A calamity is a sudden misfortune of great magnitude. It is a conditionwhich arises suddenly, and the capacity to cope is unexpectedlyoverwhelmed by the events Calamities can be natural like earth quakes,floods, cyclones, droughts, etc.

Types of Natural Calamities:

5.9.1 Floods

A scene of flood

The term "flood" is a general or temporary condition of partial or completeinundation of normally dry land areas from overflow of inland or tidalwaters or from the unusual and rapid accumulation or runoff of surfacewaters from any source.

What Causes Flood?

Heavy down pour in the form of rain bringing down more water than canbe disposed off by combined factors of natural and man made systems,causes flooding. The rivers overflow embankments may be breached.Generally rains following storm and hurricane are heavy and bringunmanageable amount of water causing flash floods.

59

EnvironmentCoping With Floods

The large amount of pooled water remaining after the flood leads to anincrease in mosquito populations. Mosquitoes are most active at sunriseand sunset. Be particularly careful to disinfect all surfaces that come intocontact with food, i.e., countertops, pantry shelves, etc. If there has been abackflow of sewage into the home, wear rubber boots and gloves duringclean up operations. Remove and discard items that cannot be disinfected.

Pump out flooded basements gradually to avoid structural damage.

Stay out of buildings if floodwaters remain around the building

In case of flood warning, place all belongings at the highest possible location,turn off electricity switches, and seal the drain holes and toilets with sandbagsto prevent sewage water from flowing back. Arrange for timely evacuation.

Setting up shelters, stocking food, water, medicines

Keeping boats and communication equipment ready

Use long stick to know the depth of water

Spread lime and bleaching powder over stagnant pools of floodwater.

Flood Forecasting Network in India

Flood forecasting has been recognized as one of the most important, reliableand cost-effective non-structural measures for flood management.Recognizing the crucial role it can play, Central Water Commission, Ministryof Water Resources has set up a network of forecasting stations coveringall important flood prone interstate rivers. The forecasts issued by thesestations are used to alert the public and to enable the administrative andengineering agencies of the States/UTs to take appropriate measures.

5.9.2 Cyclones

Cyclones are huge revolving storms caused by winds blowing around acentral area of low atmospheric pressure. In the northern hemisphere,cyclones are called hurricanes or typhoons and their winds blow in an anti-clockwise circle. In the southern hemisphere, these tropical storms are knownas cyclones, whose winds blow in a clockwise circle.

Cyclone with eye in the centerCyclone

60

Scientific Concepts How do Cyclones occur?

Cyclones develop over warm seas near the equator. Air heated by the sunrises very swiftly, which creates areas of very low pressure. As the warm airrises, it becomes loaded with moisture which condenses into massivethunderclouds. Cool air rushes in to fill the void that is left, but because ofthe constant turning of the Earth on its axis, the air is bent inwards and thenspirals upwards with great force. The swirling winds rotate faster and faster,forming a huge circle which can be up to 2,000 km across. At the centre ofthe storm is a calm, cloudless area called the eye, where there is no rain, andthe winds are fairly light.

As the cyclone builds up it begins to move. It is sustained by a steady flowof warm, moist air. The strongest winds and heaviest rains are found in thetowering clouds which merge into a wall about 20-30 km from the storm'scentre. Winds around the eye can reach speeds of up to 200 km/h, and afully developed cyclone pumps out about two million tonnes of air persecond. This results in more rain being released in a day than falls in a yearin a city like London.

Coping with Cyclones

Listen regularly to TV, Radio weather forecasts

Upon a cyclone warning take all movable property indoors and tie downthe things like boats outdoors

Store food, water and clothing.

Remain indoors and shut all doors and windows

Activity 16Prepare an emergency kit for coping with floods/cyclones with the help ofyour classmates.

5.9.3 Droughts

Drought conditions

61

EnvironmentA Drought is an extended period of months or years when a regionnotes a deficiency in its water supply. Generally, this occurs when aregion receives consistently below average rainfall.

Consequences of drought. A few common consequences of droughtinclude:

� Diminished crop growth or yield productions and carrying capacityfor livestock;

� Dust bowls, themselves a sign of erosion, which further erode thelandscape;

� Dust storms, when drought hits an area suffering from desertificationand erosion;

� Famine due to lack of water for irrigation;� Habitat damage, affecting both terrestrial and aquatic wildlife.� Malnutrition, dehydration and related diseases;� Shortages of water for industrial users;� War over natural resources, including water and food;� Wildfires, such as Australian bushfires, are more common during times

of drought;

Coping with Drought

� Cloud seeding - an artificial technique to induce rainfall.� Desalination of sea water for irrigation or consumption.� Drought monitoring - Continuous observation of rainfall levels and

comparisons with current usage levels can help prevent man-madedrought. For instance, analysis of water usage in Yemen has revealedthat their water table (underground water level) is put at grave risk byoveruse to fertilize their Khat crop. Careful monitoring of moisturelevels can also help predict increased risk for wildfires, using suchmetrics as the Keetch-Byram Drought Index or Palmer Drought Index.

� Land use - Carefully planned crop rotation can help to minimizeerosion and allow farmers to plant less water-dependent crops in drieryears.

� Rainwater harvesting - Collection and storage of rainwater from roofsor other suitable catchments.

� Recycled water - Former wastewater (sewage) that has been treatedand purified for reuse.

� Transvasement - Building canals or redirecting rivers as massiveattempts at irrigation in drought-prone areas.

� Water restrictions - Water use may be regulated (particularly outdoors).This may involve regulating the use of sprinklers, hoses or bucketson outdoor plants, the washing of motor vehicles or other outdoorhard surfaces (including roofs and paths), topping up of swimmingpools, and also the fitting of water conservation devices inside thehome (including shower heads, taps and dual flush toilets).

62

Scientific Concepts 5.9.4 Earthquakes

The sudden shaking of earth due tomoving of plates in earth's crust is calledearthquake.

More than 50%of India(foothills ofHimalyas and Ganga-Brahmputra basin)isprone to earthquakes. They occur withoutwarning. They can cause fires, floods, landslides and huge waves at sea.

Richter Scale: The instrument used for recording the earthquake is calledseismograph. It is measured usually from 0-10 on a scale called RichterScale

Earthquake

Seismograph (Richter Scale)

Surviving an earthquake: During an earthquake

� Get away from glass objects, windows and things that can fall� If you are indoor, crawl under the table or bed or crounch near an

inner wall. cover your head and face with arms.� If you are outdoor, move away from buildings, trees, poles,

hoardings� Listen to the emergency broadcasts.



1. Choose the correct answer:(i) The effect of a cyclone can be lessened by

a) costal crop fields b) costal fisheriesc) costal forests d) coral reefs

(ii) Which of the following is not a weather associated hazard?a) high tide b) droughtc) flood d) earthquake

2. Fill in the Blank(i) The instrument used to measure the earthquake is called ----

63

Environment5.10 ANSWERS TO CHECK YOUR PROGRESS

Answer 11. (i) Sulphur dioxide

(ii) Nitrogen oxide(iii) Mathura(iv) Decreases(v) Taj Mahal

Answer 21. Chloro Fluoro Carbons2. (i) CFC

(ii) Phytoplankton(iii) UV rays(iv) UV rays

Answer 31. (i) d

(ii) c(iii) a(iv) b

Answer 41. (i) C

(ii) D2. (i) Richter scale

5.11 LET US SUM UP

After reading this unit you have learnt that� Environment Pollution is mainly of three types: air, water and land

pollution� Rain gets acidified due to pollution in atmosphere� We are getting exposed to harmful rays due to ozone layer

depletion.� Greenhouse Effect is a prime cause behind global warming.� Measures should be taken to control the effects of global warming.� Measures have been undertaken at international, national,

community and local level to improve the environment.� The causes of natural disasters like floods, earthquakes, cyclones,

droughts and measures adopted to cope with these calamites.

5.12 GLOSSARY

Acid rain Rain having acids like HNO3 and H

2SO

4

Ozone layer Ozone present in stratosphere at a height of 15-30 kms.

Greenhouse A glass enclosed greenhouse where glass panes, CO2,

water vapours allow solar radiations to enter butprevent the escape of long wave heat radiations

64

Scientific Concepts Stratosphere A layer of earth's atmosphere

Ozone hole A layer of ozone in stratosphere

CFCs chlorofluorocarbons

UV rays Ultraviolet Rays

5.13 REFERENCES

We and Our World – 8 by Chandana Banerjee

Science – Text Book of 8th, NCERT.

JBD New Concepts in Biology – XII

We and Our World – 6 by Chandana Banerjee.

65

Acids, Bases and Salts

Block

2SCIENTIFIC PRINCIPLES

1. Unit 1Chemical Reactions 67-76

2. Unit 2Modified Root, Stem and Leaf 77-89

3. Unit 3Circulatory System 90-99

4. Unit 4Biodegradation, Solid waste management, Vermi 100-116composting and Rainwater harvesting

66

Scientific Concepts

67

Acids, Bases and SaltsUNIT 1 CHEMICAL REACTIONS

Structure

1.1 Introduction1.2 Objectives1.3 Chemical Reactions

1.3.1 Writing of Molecular Formulae1.3.2 Writing of Chemical Equations1.3.3 Balancing of Chemical Equations

1.4 Crystallization1.5 Solubility1.6 Let Us Sum Up1.7 Answers to Check Your Progress1.8 Glossary

1.1 INTRODUCTION

Everyday we come across many changes in our surroundings. These changesmay involve one or more substances. Preparing curd from milk is a change,stretching a rubber band also represents a change, rusting of iron is also achange. These changes are of two kinds, physical and chemical. In thisunit, we shall deal with chemical changes only. A change in which one ormore new substances are formed is called a chemical change. A chemicalchange is also called a chemical reaction. Chemical changes are veryimportant in our lives. Medicines are the end product of a chain of chemicalreactions. In this unit you will learn primarily about chemical reactions,crystallization and solubility.

1.2 OBJECTIVES

After going through this unit, the teacher will be able to:� define chemical reactions� write molecular formula� balance chemical equation� perform activities relating to chemical equation� explain the process of crystallization.� perform activities related to crystallization.� identify soluble and insoluble substances.� identify solute and solvent in a solution.

1.3 CHEMICAL REACTIONS

When a substance reacts with another substance and some new substancesare produced, we say that a chemical reaction has taken place. Thus, itinvolves re-grouping of atoms or ions to form other new substances.Chemical reactions occur under different conditions. Substances which reactor undergo a change are called reactants. The new substances which are

68

Scientific Principles formed during a chemical reaction are called products. To understand theconcept – chemical reactions, we must understand the formula of a substance.The formula represents the elements present as well as the ratio in whichthe atoms of these elements are present.

1.3.1 Writing of molecular formula.

Let us start by taking an example. A molecule of hydrochloric acid is madeup of one atom of hydrogen and one atom of chlorine, so its formula iswritten as HCl.

Activity 1� You will divide the students into small groups.� Provide one worksheet to each group.� The students will discuss among themselves and complete the worksheet

WorksheetRead the instruction, discuss among yourselves and complete the task

Write down the molecular formula of� A molecule of water consists of two atoms of hydrogen and one atom

of oxygen.� A molecule of methane consists of one carbon atom and four hydrogen

atoms.� A molecule of sulphuric acid made up of two atoms of hydrogen, one

atom of sulphur and four atoms of oxygen.

After completing the worksheet, the groups will present it and you willfacilitate the discussion.

Some compounds, such as sodium chloride (NaCl) consist of ions. In thecrystal of sodium chloride, Na+ and Cl- ions are arranged in a particularway and the total number Na+ and Cl- ions is same. Since Na+ and Cl- arepresent in 1:1 ratio, this is indicated by the formula of NaCl.

While writing the formula of a compound, we have to keep in mind that thecompound is electrically neutral. So the ratio of cations and anions shouldbe such that overall positive charge is equal to the overall negative charge.It means that if the charges in cations and anions are not the same, thentheir ratio would also be different. The charge on any ion is equal to itsvalency. For example, we have seen in case of NaCl, the ratio of charge,positive to negative is 1:1. The same holds for sulphuric acid (H

2SO

4). The

charge ratio of H+ ions and SO4-- radical is 2:2 = 1:1. And for Potassium

Hydroxide (KOH), K+ is +1 and OH- is -1. As the ratio is again 1:1.

For exampleFormula of Barium Chloride� Barium Chloride consists of two ions, barium as cation and chloride as

anion. The valency of Barium is 2+ and that of chloride is 1-. Hence,we can write the formula in the following two steps:

69

Chemical ReactionsStep 1: Ba2+ Cl-

Step2: Ba1Cl

2

We shall drop the suffix '1'as per convention. Hence, the formula of BariumChloride is BaCl

2.

Activity 2� You will form small groups.� To each group,you will give two tables..� The students will go through the charts and write the molecular formula

of following molecular compounds.Sodium Sulphate, Calcium Sulphite, Aluminium Carbonates, PotasiumHydroxide, Calcium Nitrate, Silver Chloride, Magnesium Hydroxide,Zinc Carbonate, Aluminium Phosphate.

Table 1: Names, Formulae and charges of some common Cations

Name Formula ChargeSodium ion Na + 1+

Potassium ion K + 1+

Silver ion Ag + 1+

Calcium ion Ca 2+ 2+

Barium ion Ba 2+ 2+

Magnesium ion Mg 2+ 2+

Zinc ion Zn 2+ 2+

Aluminum ion Al 3+ 3+

Table 2: Names, Formulae and charges of some common Anions

Name Formula ChargeFluoride ion F - 1-

Chloride ion Cl - 1-

Hydroxide ion OH - 1-

Nitrate ion NO3 - 1-

Sulphide ion S2- 2-

Carbonate ion CO32 - 2-

Sulphate ion SO42 - 2-

Phosphate ion PO43 - 3-

After completing the task, each group will present it you will� Facilitate the discussion.� With the help of students, consolidate the steps for writing the formula

of any ionic compound.

Step I: Write the symbols of cations and anions with their valenciesat the top

Step II: Write the value of the valency of each ion as subscript of theother ion.

The symbol of cation is multiplied by the valency of anion and symbolof anion is multiplied by the valency of cation.

70

Scientific Principles

1.3.2 Writing of chemical equations

A chemical reaction, when written using the symbols or formulae of reactantsand products is called a chemical equation. To write a chemical reaction inthe form of an equation the different reactants are written with plus (+) signbetween them on the left side of an arrow ( ). The products formed arewritten on the right side of the arrow with plus (+) sign between them. Thereactants and products are represented by their symbols or formulae. Let usunderstand it with the help of examples.

When zinc reacts with Hydrochloric acid, zinc chloride and hydrogen areproduced. Here zinc and hydrochloric acid are reactants whereas zincchloride and hydrogen are products.Zinc + Hydrochloric acid Zinc Chloride + Hydrogen(Zn) (HCl) (ZnCl

2) (H

2)

Reactants Products

Such a chemical equation is called a Skeleton chemical equation. In this,the number of atoms of hydrogen and chlorine on their respective sides arenot equal. When these are made equal, the equation is said to have beenbalanced.

Activity 3� Divide the students into small groups� To each group ,give a few chemical equation like

o Magnesium reacts with hydrochloric acid to form magnesiumchloride & hydrogen.

o Sodium hydroxide reacts with sulphuric acid to give sodiumsulphate and water.

o Sodium reacts with water to form sodium hydroxide and hydrogengas is liberated.

� Then ask the students to discuss in the group and for each chemicalreaction, tell them to identify the reactants and products and write itin the form of chemical equation.

� After doing the task, students will present it in the class.



1. Write the molecular formula of the following compounds :(i) Potassium nitrate, (ii) Sodium Sulphate,(iii) Ammonium Chloride, (iv) Magnesium Sulphite,(v) Barium Phosphate.________________________________________________________________________________________________________________________________________________________________________________________________________

71

Chemical Reactions� You will facilitate the discussion.� At the end, with the help of students, you will discuss the principles of

writing the chemical equation.

Now let us take stock of the information provided by a chemical equation.

A chemical equation gives the following information:� The elements, compounds, taking part in the chemical reaction are

the reactants� The new compounds or elements formed in the reaction are the

products.� Reactants are placed on the left-side with plus sign between them.� Products formed are written on the right side of arrow with plus sign

between them.

Activity 4Whole class open discussion.� The students will sit in a circle.� You will discuss with them regarding the purchasing of vegetables,

fruits. How the shopkeeper will give them 2 Kg of Potatos/500 gm ofOnions/ 3.5 Kg of apples.

� You will also discuss in the class use of balance in measuring thequantity of vegetables/fruits/any material.

1.3.3 Balancing of chemical equation

In a chemical reaction some substances react to form new substances butthe total number of atoms of each element on both the sides should remainthe same. When an equation is written with the help of symbols, formulaeof reactants and products, it may not show the same number of atoms ofeach element on both the sides, this is called an unbalanced equation. Thenthey are made equal by multiplying the symbols, formulae of some of theelements are compounds by whole numbers. Formula of any compound isnot changed but the number of molecules of a compound may be changed.

Activity 5� Ask the students to sit in U shape.� You write one chemical reaction on the blackboard, i.e. sodium reacts

with water to form sodium hydroxide and hydrogen gas is liberated.� Ask the students to tell the chemical equation and you write it on the

blackboard.Na + H

20 NaOH + H

2

� Then you ask the students to count the number of atoms of each elementon both the sides and write it in a tabular manner on the blackboard.

Let us balance the chemical equation.

Reactant side Product sideNo. of Na atoms 1 2No. of H atoms 2 3No. of O atoms 1 1

72

Scientific Principles Students will form groups. You will ask the following questions. Tell thestudents to discuss and present� What did we find from this table?� Is it a balanced equation, yes/no and why?� From the table, it is found that the number of sodium and oxygen atoms

are same on both the sides but the number of hydrogen atoms is different(2 in reactant but 3 in product side) so it is not a balanced chemicalequation.

� Then you will ask the students to discuss in groups and how to makethe equation a balanced one.

� With the help of students, you will facilitate the discussion.� In order to increase the no. of hydrogen atoms on let-hand side, we

multiply H2O by 2.

Na + 2H20 NaOH + H

2

� That makes four atoms of hydrogen and two atoms of oxygen on leftside. Now to increase the number of hydrogen & oxygen atoms on righthand side, we multiply NaOH by 2. The equation becomes

2Na + 2H20 2NaOH + H

2

� We find that the numbers of hydrogen and oxygen atoms are same onthe two sides but sodium atoms are not equal. For that, we multiply Naby 2 because on right side, there are two atoms of Na.

2Na + 2H20 = 2NaOH + H

2

Please note that at this stage we change the arrow ( ) sign to equality (=)sign. It is also to be noted that the method of multiplying by 2 and thesubsequent steps are not to be considered sacrosanct, depending on thesituation, these multipliers have to be chosen in an institutive manner. Pleasesensitize our student to develop their numerical capability.

� Now you will ask the students to count the number of atoms of eachelement on both the sides.

Reactant ProductsNo. of Na atoms 2 2No. of H atoms 4 4No. of O atoms 2 2

� Now you will ask the students to discuss whether the equation isbalanced or not, if yes then how.

� This equation contains the same number of atoms of each element onboth the sides hence this represents a balanced chemical equation.

� Then with the help of students, you will consolidate about balancedchemical equation.

� A balanced chemical equation should be balanced in respect of mass,as well as charge

73

Chemical Reactions

1.4 CRYSTALLIZATION

We know that salts can be obtained by the evaporation of sea water. Thesalt obtained in this way is not pure and its crystals are of small size. Butwe can get the large crystals of pure substances from their solutions. Thisprocess of getting crystals from their solutions is known crystallization.

Activity - 6 (Teacher demonstrated Activity)� Ask students to sit in U shape.� Then you will demonstrate one experiment/activity in the class. For

this, one beaker, sodium chloride and filter paper will be required.� You will prepare a solution of sodium chloride and add sodium chloride

continuously and stir it. Continue adding sodium chloride till no moresalt can be dissolved.

� Then filter the solution through a filter paper to remove any undissolvedsalt or other impurities.

� Leave the beaker containing the solution undisturbed. In a couple ofdays, crystals of pure sodium chloride will form and settle down at thebottom.

(While performing the activity, you will ask questions relating to theexperiment)

Activity 7Teacher can perform the same activity by dissolving copper sulphate inwater, following the same procedure. After the solution is saturated, thenheat it. The water will be evaporated. Filter the solution. Beautiful bluecrystals of copper sulphate will be formed.

Activity 8 (Teacher demonstrated Activity)� Take one beaker. Pour cold water into the beaker� Add potassium nitrate (KNO3) and stir continuously till no more salt

will dissolve.� After saturation, heat the solution.� The crystals of KNO3 will be formed immediately.



1. Balance the following chemical equationsi. KClO

3= KCl + O

2

ii. H2O2

= H2O + O2

iii. HgO = Hg + O2

iv. Zn + HCl = ZnCl2 + H

2

v. H2S + SO

2= 2H

2O + S

________________________________________________________________________________________________________________________________________________________________________________________________________

74

Scientific Principles Activity 9 (Teacher demonstrated Activity)� Take one microscope or lens. Keep it on the table.� Take crystals of copper sulphate or potassium nitrate on a watch glass

or a slide.� Watch the crystals through microscopic or lens.� After observation by each student, then whole class discussion will be

done.� The growth of crystals will be observed clearly through microscope.

Conclusion� Some substances can be obtained in pure state from their solutions by

crystallization.� Crystallization is a process of physical change.

1.5 SOLUBILITY

Substances which are completely dissolved in water are called solublesubstances. Substances which do not mix with water are called insolublesubstances.



1. Define the process of crystallization.______________________________________________________________________________________________________________________________________________________

2. Write the name of three crystals.______________________________________________________________________________________________________________________________________________________

Activity 10� Make students sit in a circle.� Ask each student to name substances which are completely dissolved

in water.� Then discuss in the class.

Activity 11� Divide students into groups.� To each group give, salt, sugar, turmeric powder, flour powder, water

and one glass.� Tell the students tol put water in the glass and add salt, sugar etc. one

by one.� And observe which substances completely mix with water.� After performing the activity, the students will present their report in

the class.

75

Chemical Reactions� With the help of students, you will give ideas about solute and solventand solution.Eg.: When sugar is added to water, sugar solution will be formed.Sugar is known as solute and water is the solvent.

Activity 12� Divide the students into small groups.� To each group give one beaker, half a cup of water and salt.� Ask the students to go on adding salt to water and stir it well, until the

salt dissolves completely.� After some time, some salts remain undissolved and settles at the bottom

of the beaker. No more salt can be dissolved in the amount of watertaken.

� The solution is now turned into saturated.

Conclusion

� Substances which are completely dissolved in water are called solublesubstances, which do not dissolve in water are known as insolublesubstances.

� In a solution, the solids which dissolve is known as solute and in whichit is dissolved is known as solvent.

� A solution is said to be saturated when no more substances can dissolve.

1.6 LET US SUM UP

In this unit, you learned that:

� Molecular formula indicates the actual number of atoms of all theelements present in a molecule of the molecular substanceso Reactants: Substances are consumed in a chemical reactiono Products: Substances are produced in a chemical reaction



1. Write the name of some soluble substances______________________________________________________________________________________________________________________________________________________

2. When does a solution becomes saturated ?______________________________________________________________________________________________________________________________________________________

3. Give examples of some substances which act as solvent ?______________________________________________________________________________________________________________________________________________________

76

Scientific Principles o Chemical Equation: Description of a chemical reaction byplacing the formulas of reactants on the left and the formulasof products on the right side of an arrow.

� An equation is said to be balanced when it shows thato No atom is created or destroyed, ando Electrical change is neither created nor destroyed.

� Crystallization is a physical change in which pure form of substancecanbe obtained from its solution.

� Solubility is a phenomenon in which a substance completelydissolves in water, the substance is solute and the liquid is solvent.


Answer 1(i) KNO

3(ii) Na

2SO

4

(ii) NH4Cl (iv) MgSO

3

(v) Ba3(PO)

4

Answer 2(i) KClO

3= KCl + O

(ii) 2H2O

2= 2H

2O + O

2

(iii) 2HgO = 2Hg + O2

(iv) 2Zn + 2HCl = 2ZnCl2 + H

2

(v) 2H2S + SO

2= 2H

2O + 3S

Answer 31. The process by which crystals of a substance are

obtained from its solution.2. Sodium Chloride, Copper Sulphate, Potassium

Nitrate.Answer 4

1. Salt Sugar2. A solution becomes saturated, when no more of that

substance dissolves in the solvent, at thattemperature.

3. Water, alcohol, benzene

1.8 GLOSSARY

Chemical Reaction A reaction in which two or more substancescombined to form new substance. Substances whichundergo a change or react are called reactants andthe new substance formed are called product.

Chemical Formula It represents the ratio in which the atoms of anelement are present in a compound.

Crystallization It is the process of obtaining crystals of substancesfrom their solutions.

Solubility The process in which the substance completelydissolves in another substance (liquid)

Solute The substance which dissolves is soluteSolvent The substance in which the solute is dissolved.

77

Chemical ReactionsUNIT 2 MODIFIED ROOT, STEM &LEAF

Structure

2.1 Introduction2.2 Objectives2.3 The Root System

2.3.1 Modified Roots2.4 The Shoot System

2.4.1 The Stems2.4.2 Modified Stem


2.1 INTRODUCTION

You must have seen varieties of plants in or around your immediateenvironment, most of these bear flowers and some do not produce flowersat all. So these are named as Flowering Plants and Non-Flowering Plants.The entire body of a plant can be broadly divided into two parts (i) rootsystem and (ii) shoot system. Some times the roots, stems, leaves aremodified in need of a particular function for the plant. After reading thisUnit you can understand how the roots, stems and leaves are modified indifferent ways to perform different types of functions.

2.2 OBJECTIVES

After reading this unit you will be able to:� present different types of activities (Initiation, Practice and Evaluation)

to teach modified roots, stems and leaves.� recognize modified roots and stems in the environment.� compare modified roots and stems.� identify plants with modified roots, stems or leaves.� explain the various functions of modified roots and stems.

2.3 THE ROOT SYSTEM

Root system is that part of the plant which grows under the soil. It consists ofPrimary roots, Secondary roots, Tertiary roots, (Root-hairs) and Root caps.

Activity 1� Form small groups (5/6 students in a group)� Select the group leader� Let each group search any one plant (Tomato/Mustard/Balsam) in the

environment and pour water near it.� Then tell them to pull out the plant very gently and carefully

78

Scientific Principles � Let them wash the plant to remove soil attached to it.� Let each and every child of the group observe the different parts of the

root and draw diagram and label it.

Characteristics of a Root

� Root is non green or usuallywhitish in colour.

� It is the cylindrical part of theplant

� It grows downwards into the soil,away from the light.

� It grows from the radicle of theseed

� Roots do not bear leaves, buds orflowers and fruits.

� Roots are not distinguished into nodes and internodes.� The main root called the Primary root� The side roots of Primary root are called Secondary Roots.� The Secondary roots further produce branches called the Tertiary roots.� The tip of each root bears the growing point and is protected by Root

cap.� Each root bears cluster of fine delicate, tubular and thread like structures

called the Root hairs.� Roots fix the plant in the soil� Root hairs absorb water and mineral salts from the soil.

Activity 2� Ask students to sit in small groups.� Supply each group with one gram plant and a maize plant� Instruct students to observe both the plants and draw the diagram� Ask them to write the difference between two roots.

Fig. 2.1 Structure of a taproot

Project Work: Take some pea seeds and wheat grains and place them intwo separate beaker filled with soil. Put some water every day andobserve. After a few days these will germinate and seedlings will emerge.After the development of seedlings of each type, pull out the seedling,wash the roots gently and examine the roots, using magnifying glass.You will find the pea seeds develop Taproot system and maize grainsdevelop adventitious root system. Draw these in your note book.

79

Modified Root, Stem & Leaf

Activity 3� Instruct all the students to observe the environment for 5 minutes. and

write the name of plants having tap root system and fibrous root system(5 from each).

� Divide students into small groups to prepare the group report.� Each group leader will present the group list.� You will do the correction work.

2.3.1 Modified Roots

Sometimes roots are modified to perform certain special functions inaddition to the normal functions. Modification occurs in their shape, size,form or structure.

(A) Tap roots show three types of modification i.e.1- Fusiform. 2. Conical 3. Napiform.

1. Fusiform - In this type, the taproot is swollen in the middle andgradually tapers towards both ends.e.g. - Radish.

Fig. 2.2 Parts of a flowering plant

Fig2. 3 Fusiform root (Radish)

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Scientific Principles 2. Conical - In this form, the rootassumes a conical shape, whichis broadest at the base and graduallytapers to a point at the tip.e.g.- Carrot.

3. Napiform - The tap root is extremelyswollen and assumes the sphericalshape, but abruptly tapers towards thelower end.e.g.- Beet root.

(B) Adventitious roots are also modified like tap roots. These are .(i) Tuberous root (ii) Fasciculated/clustered roots.(iii) Moniliform or Beaded roots.

(i) Tuberous roots - The root has become swollen and fleshy assumingvarious fusiform, rounded or irregulare.g. -Sweet potato

Fig 2.4 Conical root (Carrot)

Fig 2.5 Napiform root (Beetroot)

Fig 2.6 Tuberous roots (Sweet potato)

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Modified Root, Stem & Leaf(ii) Fasciculated or Clustered roots -These are also tuberous roots, butoccur in clusters or fascicles.e.g.- Asparagus.

(iii) Moniliform or Beaded roots-The adventitious roots assumethe beaded appearance with alternatelyswollen and constricted parts as in somevariety of grasses.

Function - All the above mentioned modified tap root and adventitious rootsare modified to store food

Fig 2.7 Fasiculated roots (Asparagus)

Fig 2.8 Beaded roots (Grass)



1. Give two differences between the Taproot system andAdventitious root system, with examples______________________________________________________________________________________________________________________________________________________

II. Aerial Root Modification

Aerial roots are adventitious roots which develop from the aerial parts ofthe plant. On the basis of their functions, they are recognized as (a) Proproots (b) Stilt roots (c) Clinging roots.

(a) Prop rootsThese roots develop from thebranches of a tree and growdownward and reach the soil. Theyprovide mechanical support to thebranches and serve as "pillars". e.g.-Banyan tree.

Fig 2.9 Banyan Tree (showing prop roots)

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Scientific Principles Do you know

The great Indian Banyan tree located in the Indian Botanical GardensKolkata has developed over 800 Prop roots. The plant looks like a "mini"forest. As a matter of fact the main trunk seems to have got lost.

(b) Stilt roots These rootsnormally arise from theproximal nods and growobliquely downwards. Onreaching the soil these act as"stilts" and provide support tothe plant. e.g.-pandanus.Sugarcane, Maize

(c) Clinging roots or climbing roots� These are developed in weak -

stemmed plants� These roots help the plants in

clinging and climbing. e.g.- Betel, Money plant.

Functions of roots� Fixation or Anchorage.� Absorption� Respiration� Conduction� Storage of food� Prevention of soil erosion� Providing additional support/Mechanical support.



1. Write examples for each(i) Prop roots(ii) Stilt roots(iii) Climbing roots

_______________________________________________________________________________________________________________________________________________________________

Fig 2.10 Maize & Pandanus (Stilt roots)

Fig 2.11 Clinging roots (Money Plant)

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Modified Root, Stem & Leaf

Fig 2.12 Parts of a stem

Activity 4� You will form small groups (4/5 in one group)� Supply some plants/roots having modified Tap root system and

Adventitious root system like (Radish, Carrot, Beet, Sweet potato,Asparagus, Grass, Banyan tree (Picture), Sugarcane, Maize plant,Money plant, Brinjan Plant Green chilli plant, Paddy plant, Ladiesfinger plant etc.

� Ask students to observe each plant and discuss.� Instruct them to classify it according to its similarities.� Tell them to explain why they classify like this/ on what basis� Group presentation (by the group leader) followed by your discussion� You will explain different types of modified roots and their functions.

Activity 5 Practice activity by students� Ask students to sit in small groups.� Tell each group to write the names of different storage roots .� Group presentation.� Supply each group with modified roots (Radish, Carrot, Beet) modified

stems (Ginger, Potato, Onion) and one Flowering Plant� Then ask students to write the different parts of the plant (both root

and shoot system)� Instruct them to examine and compare the parts present in modified

roots and modified stems with the parts of the supplied plant.� Ask them to explain the aspects of similarity? (How Radish, Carrot,

Beet similar to roots)

2.4 THE SHOOT SYSTEM

The shoot system is the green part ofthe plant body found above the ground.The term "shoot" is a collective termfor the stem and whatever it bears.

2.4.1 The stem

The stem develops from the plumule of a germinating seed.

The stem where the leaves are attached, called as nodes. The part of thestem between the two nodes is the internodes.

The upper angle that the stalk of the leaf forms with the stem is called theaxil. The axil of a leaf bears a bud known as axillary bud.

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Scientific Principles Activity 6� Ask students to sit in small groups� Supply each group with a branch/stem� Ask them to draw the diagram individually on their notebooks� Instruct the students to label nodes, internodes, axil and axillary bud.� You will organize group discussion and do corrections work.

Part -II

� Supply each group with ginger, potato, colocasia and onion.� Ask the students to observe minutely the structure of nodes, internodes,

terminal buds and axillary buds in potato, ginger, colocasia and onion.� Draw the following inferences after group discussion.

� Potato, ginger, colocasia, onion grow inside the soil and storefood

� Due to the presence of nodes, internodes, axillary buds, theseare called modified stems

2.4.2 Modified stems

The students will observe minutely the structure of nodes, internodesterminal buds, axillarybuds in ginger , potato, colocasia and onion.

Fig 2.13 Potato, Onion & Colocasia(Modified stems)

Project Work

Take a potato and put a stick piercing the potato and keep it underwater in a beaker and keep it in the sunlight. After few days you cansee a plant growing from the eye of the potato. This shows that thepotato is modified stem that so why the stem is growing from thepotato. The eye is the auxiliary bud of the potato.

Likewise, you can try with onion and ginger to observe the modifiedstem.

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Modified Root, Stem & LeafFunctions of stem� Support� Manufacture of food� Conduction� Storage of food� Perennation� Vegetative propagation



1. Draw the diagram of any stem and show the different parts.

2. Explain the characteristics of :(i) Nodes,(ii) Internodes(iii) Axil,(iv) Axillary buds

______________________________________________________________________________________________________________________________________________________

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Scientific Principles Activity 8� Form small groups (5/4 in each group)� Students will be supplied with some modified roots and stems� They are directed to examine and separate the modified roots and

modified stems and write the names in their note book� Group presentation with follow up discussion by the teacher.

Activity 9� Divide the students into small groups.� Provide each group with diagram of modified roots and stems and

give them some chits, where different functions of roots and stemsare written.

� Ask them to match the roots and stems with their functions.� Instruct each group to present one type of modified root or stem and

its function.� You will consolidate the group work on the black board and all the

students will write in their note books.

Activity 10You will show the parts of tendrils in cucurbita and possiflora (Kakrior lauki) and also a cactus plant showing spines.

Fig 2.15 Pitcher plant Fig 2.16 Pea plant

Activity 11� Form small groups.� Supply each group with one Cactus plant and a Rose plant.� Ask students to draw both the diagrams in their note book and label

it properly.� Group presentation.

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Modified Root, Stem & Leaf� You will explain about modified leaves (leaf Tendrils, Bryophyllum,spines and pitcher plant)

2.5 LET US SUM UP

In this unit, you have learnt that� The characteristics of different types of modified roots and stems� Identification of plants with modified roots and stems� Various functions of modified roots and stems� Classification of modified roots and stems as shown

Modification of Root

Underground Roots Aerial Roots.

Tap Roots Adventitious Roots 1. Prop roots(Banyan)

1. Fusiform 1. Tuberous 2. Stilt roots(Radish) (Sweet potato) (Pandanus)

2. Conical 2. Fusciculated 3. Clinging (Carrot)(Asparagus) (Piper money plant)

3. Napiform 3. Moniliform(Beet root) (Cayratia)

Modification of stems

Underground Aerial

1. Rhizome - Ginger 1. Tendril - Passiflora

2. Tuber - Potato 2. Thorn - Carissa

3. Bulb - Onion 3. Phylloclade - Opuntia

2.6 ANSWER TO CHECK YOUR PROGRESS

Answer 11.

Taproot system Adventitious root system

The root developing from the Any root which is not developingradicle of germinating seed is from the radicle is known ascalled taproot adventitious root

It produces branches like underground modification also takessecondary and Tertiary roots place in adventitious roots Like

Tuberous roods (sweet potato)

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Scientific Principles Answer 2(i) Prop roots - Banyan tree(ii) Stilt roots - Maize plant, Pandanus(iii) Climbing roots - Money plant, Betel

Answer 3 1.

2. (i) Nodes - The point on the stem from where the leaf arises iscalled a node.

(ii) Internode - The leafless part of the stem between any onenode and the next is called an Internode.

(iii) Axil - The upper angle that the stalk of the leaf forms withthe stem is called the axil.

(iv) Axiliary bud - The axil of a leaf bears a bud known as axillarybud

2.7 GLOSSARY

Perennation It is a kind of vegetative reproduction, i.e.reproduction from parts other then seeds.

Vegetative propagation Help to propagate the plant without seed.

Anchorage Root fixes the plant firmly in the soil and helpsto hold the plant upright.

Prop roots Look like the pillars providing additionalsupport to the branches.

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Modified Root, Stem & Leaf2.8 REFERENCES

Vishnoi H.S. (2005) Concise Biology, Selina publishers, Daryaganj,New Delhi.

Teaching of Life Science (2006) IGNOU, New Delhi

Nair, Achar, Hegde & Prabhu, (2003) A text book of Biology HimalayaPublishing House, Mumbai.

Visual Dictionary, Dorling Kindersley, New York-2006.

Science Class-VI Govt. of Orissa 1996 SCERT, Bhubaneswar.

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Scientific Concepts UNIT 3 CIRCULATORY SYSTEMStructure

3.1 Introduction3.2 Objectives3.3 Structure of Heart3.4 Circulation of Blood

3.4.1 Double Circulation of Blood3.4.2 Pulmonary Circulation3.4.3 Systemic Circulation


3.1 INTRODUCTION

The circulatory system consists of the heart and blood vessels, which togethermaintain a continuous flow of blood around the body, the heart pumpsoxygen-rich blood from the lungs to all parts of the body through a networkof tubes called arteries. Blood returns to the heart with the help of small andlarge vessels called veins. Arterioles and venules are linked by a network oftiny vessels called capillaries, where the exchange of oxygen and carbondioxide between blood and body cells takes place.

3.2 OBJECTIVES

After reading this unit you will be able to.� explain the principles of blood circulation in our body.� differentiate the function of veins and arteries.� get activities conducted by the students about circulation of blood.� recognize/identify the different parts of the heart.� develop and conduct activity to show the circulation of blood from

heart to lungs.� explain double circulation of blood in our body.

3.3 STRUCTURE OF HEART

The heart is a hollow muscle in the middle of the chest that pumps bloodaround the body, supplying cells with oxygen and nutrients.

A muscular wall, called the septum divides the heart length ways into leftand right sides. A valve divides each side into two chambers: an upperatrium and a lower ventricle. So there are four chambers in the heart, i.e.Right atrium, Right Ventricle, Left atrium and Left ventricle. The valvespresents in between atrium and Ventricle are called Tricuspid valve andbicuspid valve respectively.

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Circulatory SystemActivity 1� Ask the students to sit in small groups (4 in one group)� Give the cut pieces of heart diagram to each group� Instruct them to join all the pieces and see what the structure is

Activity 2� Supply the same group with one dotted

diagram� Ask the students to connect the numbers

in ascending order andobserve what it appears like

Activity 3� Supply each group with a heart diagram (inner structure)� Assign a symbol to each part of the

heart.� The symbolic names were given on the

top of the diagram.� Ask the students to label the diagram according to the symbol given on

it.

Fig.3. 1Dotted diagram of the heart

* Superior VenacavaInferior Venacava

A. Right AuricleB. Left Auricle

Right VentricleLeft Ventricle

� Pulmonary VeinPulmonary ArteryDorsal Aorta

�

Fig. 3. 2 Diagrammatic representation of Inner structure of the heart

Then hang one labeled diagram of the heart on the wall and each group willcorrect their labeling accordingly

Fig. 3.3 Internal structure of the heart

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Scientific Concepts Activity 4 (By the Teacher)You will demonstrate the heart of a Goat and will explain the shape, sizeand structure. Then you will cut the heart vertically into two parts and willshow the hollow structure of four chambers of heart (Left Atrium, LeftVentricle, Right Atrium & Right Ventricle)

You may show the model of heart which can be separated into differentparts. Ask the students to observe and themselves separate each and everypart of the heart and again join together.

Tips for Teachers

� How to draw diagram of heart.� Put a vertical line and first draw left auricle and left ventricle on

the left side of the line. Then draw the right-auricle and right-ventricle on the right side of the line. Then draw aorta valves andother parts.

� You can draw bilaterally symmetrical diagrams, using the sametips.

� Draw the parts of the diagram one by one on the board and ask thestudents to draw.

Activity 5Instruct all the students to draw the diagram of the heart in their note books.Then ask them to sketch and label it properly. You will do the correctionwork. Then organize activity with the whole class and explain the shape,size, structure and names of different parts of the heart.

Right atrium Tricuspid valveRight ventricle Bicuspid ValveLeft a atrium pulmonary veinLeft ventricle pulmonary arterySuperior vena cava etc.

Activity 6

" Divide students into small groups" Supply each group with a letter grid." Instruct students to sketch the names those words that are connected

with the parts of the heart.

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Circulatory SystemIdentify the names of different parts of the heart; these are hidden in theletter grid.

L E D F O

R I G H T A U R I C L E V W K S E X Z A N P U L A O R T A T M O N H E A R Y A R T E R Y B I V A I N C U S P I D V A L V E E

Activity 7

Supply each group with the balloon diagram.

� No. of balloons are flying in the sky,containing the parts of different internalorgans of our body.

� Ask students to collect the balloons thatcontain the parts of the heart and make abunch.

Fig. 3.4 Balloons labeled with names of

different parts of body organs



1. Fill in the blanks:(i) The valve that opens from left atrium to left ventricle is

called __________________.(ii) The name of the valve which opens from right atrium to

right ventricle is called_____________.(iii) The heart is divided into ___________________________

chambers.(iv) The muscular part named ____________________

separates left ventricle to right ventricle.

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Scientific Concepts 3.4 CIRCULATION OF BLOOD

Fig.3. 5 Structure of the heart showing Blood Circulation

� Blood circulation starts with the contraction of the two atria (auricles).� The ventricles at this time are relaxing and are empty.� The blood from the auricles passes into the ventricles easily.� When the ventricles contract, the auricles relax.� The Tricuspid valve and the Bicuspid valve preventing the return of

blood from ventricle to auricle.� The blood from the right auricle goes to lungs through pulmonary artery

for purification.� The impure blood purified at lungs, taking oxygen from it.� Exchange of gas occurs with the help of blood capillaries, present around

the air sack of the lungs.� Pure blood (oxygenated blood) comes from lungs through pulmonary

vain to the left auricle (atria).� From left auricle, the pure blood moves to left ventricle then to each

and every part of the body.

Activity 8Ask the students, "Do you want to hear your heart beat"? Instruct them toperform the following steps:

1. Take a funnel and long rubber tube about ½ m in length.2. Connect the two, by inserting the tube portion of the funnel into the

rubber tube. It should fit in.3. Put the open end of the funnel, flat on your chest and the other free end

of the rubber tube in one of your ears.4. What do you hear?5. Count the number of beats per minute.6. Are these regular?

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Circulatory System7. Count the beats per minute again after running some 50m.8. Do you find any change?

Activity 9

� Ask the students to sit in small groups.� Provide each group with one diagram showing the circulation of blood

from one part to other part with arrow ( ) mark.� The students in the group will see and discuss among themselves and

will indicate the flow of blood in the heart.� Group presentation and follow up discussion by the teacher.� The teacher must discuss the following points.

Fig.3.6 Arrow diagram showing blood circulation in the heart

Blood comes to heart withthe help of veins.

Blood goes from the heartwith the help of arteries.

How blood is purified inthe lungs taking oxygenand giving out carbondioxide with the help ofnetwork of capillaries.

Flow of Blood

Superior Vena cava Right atrium Right Ventricle

Pulmonary vein Lungs Pulmonary artery

Left atrium Left ventricle Left Carotid artery

Different parts of body

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Scientific Concepts

3.4.1 Double circulation of blood:Blood flows twice in the heart before it completes one full round.(1) The short pulmonary circulation (Lungs)(2) The long systemic circulation (General body)

3.4.2 Pulmonary CirculationIt starts in the Pulmonary arterywhich arises from right ventricle.It divides in two branches and entersto the lungs (Left and Right) In thelungs blood is purified taking oxygen.



1. Fill in the blanks.Show the Flow of blood :

Right auricle Right Ventricle Lungs _______________Left auricle ________________2. The substances to and from the tissues diffuse through the wallsof ____________.3. Write two characteristics of arteries and veins.____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________4. Choose the correct answer: (i) The nearest organ to which the heart supplies oxygenated blood is (a) Lung (b) Stomach (c) Intestine (d) Heart itself. (ii) When a doctor is recording your pulse, where exactly is he pressing on your wrist? (a)Vein (b) Capillary (c) artery (d) Nerve

Right ventricle Pulmonary artery Left and Right lungs

Oxygenated BloodLeft auricle

3.4.3 Systemic circulationIt starts with the aorta (Dorsal aorta) which arises from the left ventricle.Gives blood to the various parts of the body by the help of arteries andcapillaries. Then the blood is collected by veins and poured back in theheart.

Left ventricle

veins

Dorsal aorta

Various parts of body

Left auricle

Right ventricle

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Circulatory SystemActivity 10� Let students sit in small groups� Provide each group with the diagram (double circulation of blood),

where the flow of pure and impure blood is show with ( ) mark.� Again supply a set of "chits" (Paper slip) to each group where names

of various parts of circulatory system are written.� Ask the students in the group to observe the diagram and attach the

names in various parts.� Then they will draw the diagram showing the different parts.� Ask the group leader to present the group work,� You will correct it if required.

Then the teacher willexplain the flow of blood indouble circulatory systemand consolidate it.

Fig.3. 7 Double circulation of blood



1. Draw a flow chart showing the flow of blood in doublecirculatory system

3.5 LET US SUM UP

In this unit, you learnt that

� The circulatory system consists of four chambered heart, arteries, veinsand capillaries.

� Heart is present in the centre between two lungs and above thediaphragm

� Two valves named bicuspid valve and tricuspid valve are presentbetween left auricle left ventricle right auricle and right ventriclerespectively

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Scientific Concepts� Flow of Blood

Right auricle Right ventricle

Left Pulmonary Lungs PulmonaryAuricle Vein artery

Left Ventricle various parts of the body

� Blood flows twice in the heart before it completes one full round.(1) The short pulmonary circulation (Lungs)(2) The long systemic circulation (General body)

3.6 ANSWER TO CHECK YOUR PROGRESS

Answer 11. (i) Bicuspid Valve (ii) Tricuspid valve

(iii) Four chambers (iv)Septum.

Answer 21. Pulmonary artery, Pulmonary Vein, Left Ventricle.

2. Capillaries

3.

ARTERIES VEINS1. Carry oxygenated blood 1. Carry deoxygenated blood (except Pulmonary artery) (except pulmonary vein)

2. Blood flows with jerks and 2. Blood flows continuously and under great pressure under very little pressure

4. (i) (d)(ii) (c)

Answer 31.

Double circulation of blood

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Circulatory System3.7 GLOSSARY

Heart Heart is a hollow muscle in the thoraciccavity that pumps blood around the body.

Chambers of Heart Right & Left Auricles; Right & LeftVentricles

Double Circulation The blood goes through a short pulmonarycirculation and along systemic circulationto complete one full round in the body.

Pulmonary Circulation Circulation of blood starts from thepulmonary artery in the right ventriclegoes to the lungs, where it is purified.

Systemic Circulation Circulation starts from the dorsalaorta in the left ventricle and gives bloodto various parts of the body througharteries.

3.8 REFERENCES

Concise Biology (ICSE), 2008, Salira Publishers, Daryaganj, New Delhi.

Science (Class VI), 1996, Govt of Orissa SCERT, Bhubaneswar.

Beckett, B.S. (1985), Beginning Science Biology, Oxford University Press,Oxford.

Ultimate Visual Dictionary, Dorling Kindsley, New York.

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Scientific Principles UNIT 4 BIO-DEGRADATION, SOLIDWASTE MANAGEMENT,VERMICOMPOSTING, RAINWATER HARVESTING

Structure

4.1 Introduction4.2 Objectives4.3 Biodegradation

4.3.1 Meaning of Biodegradation4.3.2 Need for Biodegradation4.3.3 Advantages and disadvantages4.3.4 Biodegradable Materials

4.4 Solid Waste Management4.4.1 Meaning of Solid Waste Management4.4.2 Techniques of Waste Management

4.5 Vermicomposting4.5.1 Meaning of Vermicomposting4.5.2 Importance of Vermicomposting4.5.3 Techniques of Vermicomposting

4.6 Rain water harvesting4.6.1 Need of Rainwater Harvesting4.6.2 Benefits of Rainwater Harvesting4.6.3 Methods of Rainwater Harvesting


4.1 INTRODUCTION

Mahatma Gandhi once said, "The earth has enough resources forevery man's needs, but not for every man's greed."

The earth through its life spanning billions of years has undergone severalextreme and drastic changes which have severely altered its state. Thesechanges were natural and were compensated with the passage of time. Theywere also gradual and took millions of years to culminate. The formationof landmasses, oceans, mountains, valleys, rivers, deserts, and forests etc.is all a consequence of natural forces which have acted over the millenniato give the earth its present form. This process of change is dynamic andcontinuous and shall never stop till the end of the Earth.

The most consequential change has been the advent of mankind. Man is asuperior being with high intelligence. Initially man learnt to adapt himselfand survive nature. But with the knowledge and skill man learnt to modifynature to suit his needs and create a comfortable environment around himself.

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Bio-Degradation, SolidWaste Management,

Vermicomposting, RainWater Harvesting

Although this practice serves a short time purpose, but the damage done tonature is irreparable. Over a period of time, significant changes have beeninflicted on nature such as massive deforestation, altering the course andflow pattern of rivers, destruction of marine and terrestrial ecosystems byindustrial and commercial activities, etc. The adverse effects of theseactivities are evident all around us.

In this unit you are going to read about the harmful effects resulting fromthe misuse of nature's bounteous gifts by the human race. You will learnthe various techniques required to create an awareness and understandingof healthy environmental practices.

We throw out so much rubbish or garbage everyday from our homes, schools,shops and offices. The grains, pulses, biscuits, milk or oil purchased fromshops are packed in plastic bags or tins. All these wrapping material go outas garbage. We sometimes buy things that are rarely used and often throwthem into the vats.

We often throw groundnut shells, packets of chips, biscuits, fruit, and peelsafter eating them in public places. We throw away the ticket when we getoff a bus. A child might go on tearing paper and sharpening pencils just forfun. We also throw away many domestic wastes such as broken toys, shoes,slippers and old woolen and cotton clothes. What if the garbage is notremoved from our homes and surrounding? How do you think this willharm us? When the man appointed for cleaning purpose takes the garbagefrom the bins, where does the garbage go and what happens to it? Is itpossible for all of this garbage to be changed into something that will notharm us? Can we contribute towards this in any way?

In this unit we shall discuss topics which would sensitize you about theenvironmental degradation and some crucial measures taken for itsconversation.

4.2 OBJECTIVESAfter going through this unit you will be able to:

� analyse the environmental degradation caused by human activities.� identify healthy environmental practices.� identify current harmful practices.� define the terms: bio degradation, vermicomposting, solid waste

management, rainwater harvesting and apply them.

4.3 BIODEGRADATION

Bio degradation, vermin-composting, solid waste management and rainwaterharvesting are among the major activities in this category and have beenfurther discussed in detail.

Activity 1Collect the garbage from your house before it is thrown into the dustbin.Separate it into two groups so that they have

102

Scientific Principles 1. Group I: Garbage from the kitchen - like fruit and vegetable peels,egg shells, waste food, tea leaves, newspapers, dry leaves and paperbags.

2. Group 2: Pieces of cloth, polythene bags broken glass, aluminiumwrapper nails, old shoes and broken toys.

Now, divide the contents of each group into two separate heaps. Labelthem as A, B, C, D. Put one heap from Group 1 and one heap from Group2, into two separate plastic bags. Tie the mouth of these two bags tightly.Put all the four heaps in separate pits and cover them with soil. You canalso use pots instead of pits to bury this garbage heaps. Remove the soilafter four days and observe the changes in the garbage.

A black color and no foul smell indicate that rotting of garbage is complete.Put the heaps in the pits and cover with soil. Observe again after somedays and note your observation as suggested.

Did the garbage

1. rot completely and not smell?2. rot only partially ?3. rot almost completely, but still smell bad?4. not changed at all ?

Garbage in which heap was seen to rot and which did not.

Enter options (i), (ii), (iii), or (iv), in the columns of table based on yourobservations.

Garbage heap After 4 days After 8 days After 2 weeks After 4 weeksABCD

If you make any other observations do not hesitate to write down.

If the garbage was found to rot completely and did not smell mix it in thesoil where you sow your favorite plants. This could provide nutrients tothe plant. The rotting and conversion of some materials into manure is calledcomposting.

4.3.1 Meaning of Biodegradation

Biodegradation is the process by which organic substances are broken downby the enzymes produced by living organisms. The term is often used inrelation to ecology, waste management and environmental remediation(bioremediation). Organic material can be degraded aerobically, withoxygen, or anaerobically, without oxygen. A term related to biodegradationis bio-mineralization, in which organic matter is converted into minerals.

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Biodegradable matter is generally organic material such as plant and animalmatter and other substances originating from living organisms, or artificialmaterials that are similar enough to plant and animal matter to be put to useby microorganisms. Some microorganisms have the astonishing, naturallyoccurring, microbial catabolic diversity to degrade, transform or accumulatea huge range of compounds.

4.3.2 Need for Biodegradation

Due to centuries of harmful practices and techniques vast quantities of ourland and natural resources have become severely polluted. The conventionaltechniques used for repairing such pieces of land have been to dig upcontaminated soil and remove it to a landfill, or to cap and contain thecontaminated areas of a site. The methods have some drawbacks. The firstmethod simply moves the contamination elsewhere and may createsignificant risks in the excavation, handling and transport of hazardousmaterial. The cap and contain method is only an interim solution since thecontamination remains on site, requiring monitoring and maintenance.

Biodegradation is an option that offers the possibility to destroy or renderharmless various contaminants using natural biological activity. As such, ituses relatively low-cost, low-technology techniques, which generally havea high public acceptance and can often be carried out on site.

4.3.3 Advantages and Disadvantages of Biodegradation

Advantages� Biodegradation is a natural process and is therefore perceived as an

acceptable waste treatment process for contaminated material such assoil. Microbes able to degrade the contaminant increase in numbers whenthe contaminant is present.

� Theoretically, biodegradation is useful for the complete destruction of awide variety of contaminants. Many compounds that are considered tobe hazardous can be transformed to harmless products.

� Instead of transferring contaminants from one environmental mediumto another, for example, from land to water or air, the completedestruction of target pollutants is possible.

� Bioremediation can often be carried out on site, often without causing amajor disruption of normal activities. This also eliminates the need totransport quantities of waste off site and the potential threats to humanhealth and the environment

� Biodegradation can prove less expensive than other technologies thatare used for clean-up of hazardous waste.

Disadvantages� Biodegradation is limited to those compounds that are biodegradable.

Not all compounds are rapidly and completely degraded.� There are some concerns that the products of biodegradation may be

more persistent or toxic than the parent compound.� Biological processes are often highly specific. Important site factors

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Scientific Principles required for success include the presence of capable microbialpopulations, suitable environmental growth conditions, and appropriatelevels of nutrients and contaminants.

� Research is needed to develop and engineer bioremediation technologiesthat are appropriate for sites with complex mixtures of contaminantsthat are not evenly dispersed in the environment. Contaminants may bepresent as solids, liquids, and gases.

� Biodegradatiom often takes longer than other treatment options, suchas excavation and removal of soil or incineration.

4.3.4 Biodegradable Materials.

Biodegradable materials are substances that will decompose in a naturalenvironment without emitting or leaving behind harmful substances. Theyare usually natural products or synthetic substances with natural properties.Not only is their production economical and environment friendly, theirdisposal after their use is easy and they can be interconverted into otheruseful products. The development of such materials to substitute existingones is a prospective area of active research.

In some cities and towns municipalities provide separate dustbins forcollecting two kinds of garbage. Usually one is coloured blue and the othergreen. The blue bin is for materials that can be used again, such as plastics,metals and glass. These are the materials that do not rot in the garbageheap. Green bins are for collecting kitchen and other plant or animal wastesthat rot completely when buried in soil. Now you can understand why it isnecessary for us to separate the garbage into two groups.

How much garbage do you think is thrown out by each house every day?You can make an estimate by using a bucket as a measure.

Activity 2Use a 5-10 liter bucket to collect the garbage from your home for a fewdays. In how many days does the bucket become full? You know the numberof members in your family. If you find out the population of your city ortown can you now estimate the number of buckets of garbage that may begenerated in a day in your city or town?

We are generating mountains of garbage everyday. You might have seensome children women and men sorting the garbage near your house or otherplaces.

Activity 3Observe the children at work and find out how they separate useful materialfrom garbage. They are actually helping us. Talk to one such person andfind out as to what do they do with the rubbish they collect. Where do theytake it?

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Activity 4Have you ever helped at home to sell old newspapers, glass bottles andmetal things, plastic bags and your old note books to a garbage dealer?Talk to them and find out what he does with all the garbage.



1. Why is there a need for biodegradation?______________________________________________________________________________________________________________________________________________________

2. What are biodegradable materials? Give two examples.______________________________________________________________________________________________________________________________________________________

Activity 5Collect the household waste for 3 days and analyze it. Make a list of all theitems found and determine whether they are bio-degradable or not. Separatethe degradable and non degradable items.

Activity 6Make a list of all items in your room and ponder over how many of them arebio- degradable?

DISCUSS

� Which kind of garbage is not converted into compost by the earthworm?� Have you seen any other organism besides earthworms? Try to find out

their names and draw their pictures.� Is the garbage, disposal a responsibility only of the government/

municipality?� Is it possible to reduce the problems relating to disposal of garbage?� What do you do with the left over food at home?

4.4 SOLID WASTE MANAGEMENT

Activity 7Visit a local waste management site, a landfill or incinerator and observehow waste is processed.

Activity 8Collect household waste for a week and try to extract any items which maybe reused. Try making an artwork out of kitchen or paper waste.

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Scientific Principles The quality of life on Earth is linked to the overall quality of the environment.In early times, we believed that we had an unlimited abundance of land andresources; today, however, the resources in the world show, in greater orlesser degree, our carelessness and negligence in using them. The problemsassociated with pollution now assume increasing prominence in manycountries. Contaminated lands generally result from past industrial activitieswhen awareness of the health and environmental effects connected withthe production, use, and disposal of hazardous substances were lessrecognized than today. The problem is worldwide, and the estimated numberof contaminated sites is significant.

4.4.1 Meaning of Solid Waste Management

Waste management is the collection, transport, processing, recycling ordisposal of waste materials. The term usually relates to materials producedby human activity, and is generally undertaken to reduce their effect onhealth, the environment or aesthetics. Waste management is also carriedout to recover resources from it. Waste management can involve solid, liquid,gaseous or radioactive substances.

4.4.2 Techniques of Solid Waste Management

Waste management practices differ for developed and developing nations,for urban and rural areas, and for residential and industrial producers.Management for non-hazardous residential and institutional waste inmetropolitan areas is usually the responsibility of local governmentauthorities, while management for non-hazardous commercial and industrialwaste is usually the responsibility of the generator. Waste managementmethods vary widely between areas for many reasons, including type ofwaste material, nearby land uses, and the area available.

1) LANDFILLS : Disposing of waste in a landfill involves burying wasteto dispose of it, and this remains a common practice in most countries. Aproperly-designed and well-managed landfill can be a hygienic and relativelyinexpensive method of disposing of waste materials. Older, poorly-designedor poorly-managed landfills can create a number of adverse environmentalimpacts such as wind-blown litter,attraction of vermin, and generation ofliquid leachate. Another common byproduct of landfills is gas which cancreate odour problems, kill surface vegetation, and is a greenhouse gas. Ina landfill the deposited waste is normally compacted to increase its densityand stability, and covered to prevent attracting vermin (such as mice orrats). Many landfills also have landfill gas extraction systems installed toextract the landfill gas. Gas is pumped out of the landfill using perforatedpipes and flared off or burnt in a gas engine to generate electricity.

2) INCINERATION : Incineration is a disposal method that involvescombustion of waste material. Incineration and other high temperature wastetreatment systems are sometimes described as "thermal treatment".Incinerators convert waste materials into heat, gas, steam and ash.Incineration is carried out both on a small scale by individuals, and on alarge scale by industry. It is used to dispose of solid, liquid and gaseous

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waste. It is recognized as a practical method of disposing of certain hazardouswaste materials (such as biological medical waste). Incineration is acontroversial method of waste disposal, due to issues such as emission ofgaseous pollutants.

Combustion in an incinerator is not always perfect and there have beenconcerns about micro-pollutants in gaseous emissions from incineratorstacks. Particular concern has focussed on some very persistent organicssuch as Dioxins which may be created within the incinerator and whichmay have serious environmental consequences in the area immediatelyaround the incinerator.

3) RECYCLING : The process of extracting resources or value from wasteis generally referred to as recycling, meaning to recover or reuse the material.There are a number of different methods by which waste material is recycled:the raw materials may be extracted and reprocessed, or the calorific contentof the waste may be converted to electricity. New methods of recycling arebeing developed continuously.

The popular meaning of 'recycling' refers to the widespread collection andreuse of everyday waste materials. These are collected and sorted intocommon types so that the raw materials from which the items are made canbe reprocessed into new products. Material for recycling may be collectedseparately from general waste using dedicated bins and collection vehicles,or sorted directly from mixed waste streams. The most common consumerproducts recycled include aluminum beverage cans, steel food and aerosolcans, HDPE and PET bottles, glass bottles and jars, paperboard cartons,newspapers, magazines, and cardboard. These items are usually composedof a single type of material, making them relatively easy to recycle intonew products.

4) BIOLOGICAL REPROCESSING : Waste materials that are organicin nature, such as plant material, food scraps, and paper products, can berecycled using biological composting and digestion processes to decomposethe organic matter. The resulting organic material is then recycled as mulchor compost for agricultural or landscaping purposes. In addition, waste gasfrom the process (such as methane) can be captured and used for generatingelectricity. The intention of biological processing in waste management isto control and accelerate the natural process of decomposition of organicmatter.

BIO-MANURE IS USED TO GROW HEALTHY NON TOXIC CROPS

There are a large variety of composting and digestion methods andtechnologies varying in complexity from simple home compost heaps, toindustrial-scale enclosed-vessel digestion of mixed domestic waste. Methodsof biological decomposition are differentiated as being aerobic or anaerobicmethods.

5) ENERGY RECOVERY : The energy content of waste products can beharnessed directly by using them as a direct combustion fuel, or indirectlyby processing them into another type of fuel. Recycling through thermal

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Scientific Principles treatment ranges from using waste as a fuel source for cooking or heating,to fuel for boilers to generate steam and electricity in a turbine. Gasificationand advanced Plasma arc gasification are used to convert organic materialsdirectly into a synthetic gas (syngas) composed of carbon monoxide andhydrogen. The gas is then burnt to produce electricity and steam.

6) WASTE MINIMIZATION : An important method of waste managementis the prevention of waste material being created, also known as wastereduction. Methods of avoidance include reuse of second-hand products,repairing broken items instead of buying new, designing products to berefillable or reusable (such as cotton instead of plastic shopping bags),encouraging consumers to avoid using disposable products (such asdisposable cutlery), and designing products that use less material to achievethe same purpose.



1. Who is responsible for waste management?______________________________________________________________________________________________________________________________________________________

2. Discuss various techniques of solid waste management.______________________________________________________________________________________________________________________________________________________

Activity 9Observe how the waste of your community is collected and disposed. Suggestbetter and creative ways to do so.

Activity10Ask elders, teachers and scientists about how waste materials are beingreused in your region.

VERMICOMPOSTING

The use of chemical fertilizerscontributes largely to thedeterioration of the environmentthrough depletion of fossil fuels,generation of carbon dioxide(CO2) and contamination of waterresources. It leads to loss of soilfertility due to imbalanced use of Fig 4.1: Vermicomposting Bin

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fertilizers that has adversely impacted agricultural productivity and causessoil degradation. Now there is a growing realization that the adoption ofecological and sustainable farming practices can only reverse the decliningglobal productivity and environment protection.

On one hand tropical soils are deficient in all necessary plant nutrients andon the other hand large quantities of such nutrients contained in domesticwastes and agricultural byproducts are wasted. It is estimated that in citiesand rural areas of India nearly 700 million tones of organic waste is generatedannually which is either burned or land filled. Such large quantities of organicwastes generated also pose a problem for safe disposal. Most of these organicresidues are burned currently or used as land fillings.

In nature's laboratory there are a number of organisms (micro and macro)that have the ability to convert organic waste into valuable resourcescontaining plant nutrients and organic matter, which are critical formaintaining soil productivity. Microorganisms and earthworms are importantbiological organisms helping nature to maintain nutrient flow from onesystem to another and also minimize environmental degradation.

Municipal solid waste (MSW) is highly organic in nature, sovermicomposting has become an appropriate alternative for its safe, hygienicand cost effective disposal. Earthworms feed on the organics and convertmaterial into casting (ejected matter) which is rich in plant nutrients.

4.5.1 Meaning of Vermicomposting?

Vermicomposting is a simple biochemical process of composting, in whichcertain species of earthworms are used to enhance the process of wasteconversion and produce a better end product. The resulting earthwormcastings (worm manure) are rich in microbial activity and plant growthregulators and fortified with pest repellents as well. In short, earthworms,through a biological process, are capable of transforming garbage into'fertilizer'.

Fig 4. 2: Role of Worms in Vermi-Composting

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Scientific Principles Activity 11Construction of a Worm Bin

Bins can be made of wood or plastic, or from recycled containers like oldtubs, barrels, or trunks. Bins should be no more than 8 to 12 inches deep.Bedding and food wastes tend to pack down in deeper bins, forcing air out.Resulting anaerobic conditions can cause foul odors and death of the worms.The size also depends on the amount of food waste your family produceseach week. Wooden bins have the advantage that they are more absorbentand provide better insulation. Be sure that containers are well cleaned andhave never stored pesticides or other chemicals. Drilling air/drainage holes(1/4- to 1/2-inch diameter) in the bottom and sides of the bin will ensuregood water drainage and air circulation. Place the bin on bricks or woodenblocks in a tray to catch excess water that drains from the bin. Each binshould have a cover to conserve moisture and exclude light.

Food wastes can be continually added as they accumulate. The pile shouldbe kept damp and dark for optimum worm activity. During the winter, soilcan be piled against the edges of the bin and straw placed on top to protectthe worms from cold weather.

4.5.2 Importance of Vermicomposting

1) Source of plant nutrients

Earthworms consume various organic wastes and reduce the volume by40-60%. Each earthworm weighs about 0.5 to 0.6 g, eats waste equivalentto its body weight and produces cast equivalent to about 50% of the wasteit consumes in a day. These worm castings have been analyzed for chemicaland biological properties. The worm castings contain higher percentage ofboth macro and micronutrients.

Nutrient composition of vermicompost

Constituent PercentageOrganic carbon 9.8-13.4Nitrogen 0.51-1.61Phosphorus 0.19-1.02Potassium 0.15-0.73Calcium 1.18-7.61Magnesium 0.093-0.568Sodium 0.058-0.158Zinc 0.0042-0.110Copper 0.0026-0.0048Iron 0.2050-1.3313Manganese 0.0105-0.2038

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Vermicompost provides all nutrients in readily available form and alsoenhances uptake of nutrients by plants.

Improved crop growth and yield

Vermicompost plays a major role in improving growth and yield of differentfield crops, vegetables, and flower and fruit crops. The application ofvermicompost gave higher germination (93%) of moong bean (Vigna radiata)compared to the control (84%). Further, the growth and yield of moongbean was also significantly higher with vermicompost application. Likewise,in another pot experiment, the fresh and dry matter yields of cowpea (Vignaunguiculata) were higher when soil was amended with vermicompost.

4.5.3 Techniques of Vermicomposting

i) Pits below the groundPits made for vermicomposting are 1 m deep and 1.5 m wide. The lengthvaries as required.

ii) Heaping above the groundThe waste material is spread on a polythene sheet placed on the ground andthen covered with cattle dung. The heap method of preparing vermicompostis better than the pit method due to high earthworm production. Biomassproduction was also higher in the heap method (46-fold increase) than inthe pit method (31-fold). Consequent production of vermicompost was alsohigher in the heap method (51 kg) than in the pit method (40 kg).

iii) Tanks above the groundTanks made up of different materials such as normal bricks, hollow bricks,stones, asbestos sheets and locally available rocks are used for vermicompostpreparation. Tanks can be constructed with the dimensions suitable foroperations.

iv) Cement ringsVermicompost can also be prepared above the ground by using cement rings.The size of the cement ring should be 90 cm in diameter and 30 cm inheight.

Conclusions

The production of degradable organic waste and its safe disposal becomesthe current global problem. Meanwhile the rejuvenation of degraded soilsby protecting topsoil and sustainability of productive soils is a major concernat the international level. Provision of a sustainable environment in the soilby amending with good quality organic soil additives enhances the waterholding capacity and nutrient supplying capacity of soil and also thedevelopment of resistance in plants to pests and diseases.

Earthworms can serve as tools to facilitate these functions. They serve as"nature's plowman" and form nature's gift to produce good humus, which isthe most precious material to fulfill the nutritional needs of crops. The

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Scientific Principles utilization of vermicompost results in several benefits to farmers, industries,environment and overall national economy.

To farmers:� Less reliance on purchased inputs of nutrients leading to lower cost of

production� Increased soil productivity through improved soil quality� Better quantity and quality of crops� For landless people provides additional source of income generationTo industries:� Cost-effective pollution abatement technologyTo environment:� Wastes create no pollution, as they become valuable raw materials for

enhancing soil fertilityTo national economy:� Boost to rural economy� Savings in purchased inputs� Less wasteland formation



1. What role do earthworms play in vermicomposting?______________________________________________________________________________________________________________________________________________________

2. Discuss construction of a worm bin.______________________________________________________________________________________________________________________________________________________

Activity 12Construct a small vermicomposting bin under the guidance of your teacherand use the end product to manure plants in your garden.

Activity 13Search your community for instances of vermicomposting and observe thedetails.

Activity 14Encourage your community to reduce use of synthetic fertilizers and adoptvermicomposting on a large scale.

4.6 RAINWATER HARVESTING

Activity 15On a typical rainy day, place buckets under chajjas and try to measure thequantity of water that flows down them in an hour. Try and calculate theamount of water that is wasted in a day, month or year.

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Water is essential to all life forms on earth - human, animal and vegetation.It is therefore important that adequate supplies of water be developed tosustain such life. Development of water supplies should, be undertaken insuch a way as to preserve the hydrological balance and the biologicalfunctions of our ecosystems. Since 98% of the world's water is saline andonly 2% fresh and suitable for human use, its conservation is of utmostimportance. Water is closely associated with our lives.

Consequently, the human endeavor in the development of water sourcesmust be within the capacity of nature to replenish and to sustain. If this isnot done, costly mistakes can occur with serious consequences. Theapplication of innovative technologies and the improvement of indigenousones should therefore include management of the water sources to ensuresustainability and to safeguard the sources against pollution.

As land pressure rises, cities are growing vertical and in countryside moreforest areas are encroached and being used for agriculture. In India thesmall farmers depend on monsoon where rainfall is from June to Octoberand much of the precious water is soon lost as surface runoff. While irrigationmay be the most obvious response to drought, it has proved costly and canonly benefit a fortunate few.

There is now increasing interest in the low cost alternative-generally referredto as 'rain water harvesting' (rwh). Water harvesting is the activity of directcollection of rainwater, which can be stored for direct use or can be rechargedinto the groundwater. Water harvesting is the collection of runoff forproductive purposes.

Rain is the first form of water that we know in the hydrological cycle,hence is a primary source of water for us. Rivers, lakes and groundwaterare all secondary sources of water. In present times, we depend entirely onsuch secondary sources of water. In the process, it is forgotten that rain isthe ultimate source that feeds all these secondary sources and remain ignorantof its value. Water harvesting is to understand the value of rain, and tomake optimum use of rainwater at the place where it falls.

4.6.1 Need for rainwater harvesting:

1. Water is becoming scarce; it is the need of the day to attain self-sufficiency to fulfill the water needs.

2. Urban water supply system is under tremendous pressure for supplyingwater to ever increasing population.

3. Groundwater is getting depleted and polluted.4. Soil erosion resulting from the unchecked runoff.5. Health hazards due to consumption of polluted water.

4.6.2 Benefits of rainwater harvesting:

1. Environment friendly and easy approach for water requirements2. Rwh is the ideal solution for all water requirements.3. Increase in ground water level.

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Scientific Principles 4. Mitigates the effects of drought.5. Reduces the runoff, which other wise flood storm water drains.6. Reduces flooding of roads and low-lying areas.7. Reduced soil erosion.8. Improves the ground water quality.9. Low cost and easy to maintain.10. Reduces water and electricity bills.

4.6.3 Methods of rainwater harvesting:

1) Rainwater stored for direct use in above ground or underground sumps/Overhead tanks and used directly for flushing, gardening, washing etc.

2) Recharged to ground through recharge pits, dug wells, bore wells, SoakPits, recharge trenches, etc. (ground water recharge). The rainwater isfiltered for solid and dissolved impurities before being fed into thegroundwater system. PVC pipes are most commonly used for thispurpose.Rainwater stored for direct use in man made structures such as ponds ortanks. This water is diverted through proper site planning and contouringand allowed to collect in a large tank. This water may be used to rechargewells, irrigate fields, drinking etc. in the dry season.

Rainwater harvesting potential:In an area of 2,400 sq.ft. or 223 sq.mt. (40 ft. X 60 ft. Site) around 2, 23,000liters of Rainwater can be harvested. The amount of rainwater that can beharvested depends on the catchment area, rainfall in that area and collectionefficiency etc.



1. Why is there a need to conserve fresh water?______________________________________________________________________________________________________________________________________________________

4.7 LET US SUM UP

After reading this unit you learned that:

� Ever increasing need and greed of human beng is causing irreparabledamage to the environment.

� Biodegradation is a safe and economical way of converting wastematerial to useful products.

� Various techniques of solid waste management, through incineration,landfills, recycling etc.

� Technique of waste processing at a waste management site.� Need and importance of vermicomposting and making a worm bin.

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� Importance of rainwater harvesting in the present times.� Methods adopted for harvesting rain water.


Answer 11. Biodegradation is a useful method to destroy contaminants and harmful

substances in nature using low cost, low technology biologicaltechniques.

2. Biodegradable substances are those material which will decompose ina natural environment without leaving behind harmful substances.Examples (i) vegetable peels (ii) paper

Answer 21. The responsibility of management of non-hazardous, non-toxic wastes

from homes and institutions in metropolitan areas, lies with localgovernment authorities. Management of non-hazardous, commercialand industrial waste is the responsibility of the generator.

2. Classroom discussion on techniques of solid waste management.

Answer 31. Vermi-composting is a safe and cost-effective for disposal of solid waste.

Earthworms feed on the organic matter in the soil, and convert it in tocasting (ejected matter) which enriches the soil with organic (plant)nutrients.

2. Classroom activity

Answer 41. There is need to conserve freshwater because:

(a) Ever increasing population has led to scarcity of water.(b) Groundwater level is decreasing and getting polluted.(c) More forest land being used for agriculture, which leads to increased

demand for water.(d) Lot of rainwater lost as surface run off, leading to soil erosion.

4.9 GLOSSARY

Biodegradation Process by which organic substances are brokendown by enzyme activity of living organisms

Solid Waste Collection, transport, processing, recycling ofManagement disposal of waste materials.

Landfills Burying waste in the ground for disposal

Incineration Disposal of waste material by combustion, whichconverts the waste into heat, gas, steam and ash.

Recycling Process of recovering resources from wastematerial.

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Scientific Principles Biological Recycling organic waste material using biologicalReprocessing composting and digestion process.

Vermicomposting A biochemical process of composting in whichcertain species of earthworms are used to enhancethe process of waste conversion.

Rainwater The process, in which rainwater is collected, storedHarvesting for direct use and can be recharged into the ground

water. It helps to make optimum use of rainwater atthe place where it falls.

4.10 REFERENCES

Science Book class VI & VII : M.D. Rajya Shiksha Kendra

Science Text Book for class VI, NCERT

Wikipedia

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Block

3SKILL OF PERFORMING SCIENTIFICEXPERIMENTS

1. Unit 1Experiments in Science 118-140

2. Unit 2Respiration, Food adulteration, Transpiration and Use of 141-157Microscope

3. Unit 3Purification of Water, Artificial Greenhouse and Model of 158-165Rainwater Harvesting

4. Unit 4Science Corner 166-184

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Skill of PerformingScientific Experiments UNIT 1 EXPERIMENTS IN SCIENCE

Structure

1.1 Introduction1.2 Objectives1.3 Separation of substances

1.3.1 Substances and Mixtures1.3.2 Method of Separation of Substances

1.4 Acids and their Identification1.5 Bases and their Identification1.6 Phenolphthalein as an Indicator

1.6.1 Characteristics of Neutralization Reaction1.7 Properties of Metals and Non Metals

1.7.1 Reaction with Air1.7.2 Reaction with Water1.7.3 Reaction with Acids1.7.4 Reaction with Bases1.7.5 Reaction with Salt Solution


1.1 INTRODUCTION

You will perhaps agree with me that upper primary stage is the appropriatestage to develop critical thinking and logical reasoning in the mind of thechildren. This unit focuses on strategies of teaching scientific experimentsat upper primary level. Attempt has been made to explain and demonstratevarious experiments with the active involvement and association of childrenin the classroom. Making children realize things around them and integrationof the same with their real life situation can develop interest and curiosityin children in scientific experiments. In this unit we shall discuss experimentsin science with an emphasis on generation of curiosity among them.

1.2 OBJECTIVES

After going through this unit you would be able to:

� explain the strategies of teaching scientific experiments� explore multiple ways of teaching scientific experiments in the

classroom.� describe experiments pertaining to separation of substances, acids, bases

and salts and properties of metals

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Experiments in Science1.3 SEPARATION OF SUBSTANCES.

(Demonstration by Teacher)

How many discs are there?Label one disc as A and another as B

1.3.1 Substances and Mixtures

Put some wheat grain in disc A andask children what disc A contains.Put some pea grain in disc B and askchildren what disc B contains.Take another disc C, put grain fromdisc A and disc B in disc C.Ask children what does the disc Ccontains?How many types of substances are there in?

Disc A?Disc B?Disc C ?

Disc 'A' Disc 'B'

Fig 1.1: Representing two discs A and Bcontaining wheat grains and pea grainrespectively.

Disc 'C'

Fig. 1.2: Representing a disc C containingwheat grains and pea grain collectively.

Disc C contain two different substances. We call it a mixture of solidwith solid.

Take another disc and name it as 'D'.

Put some small pieces of stone it askchildrenWhat does disc-D contains?

Put the substance from disc D to Disc'C' and as children

What does 'C' contain now?

How many types of substances aretherein Disc 'C' now?Disc 'C' now contains more thanone type of substance we call itmixture.'A' Mixture contains substances ofmore than one type.

Disc 'D'

Fig. 1.3: Representing a disc D containingstones

Disc 'C'

Fig. 1.4: Representing disc 'C' containingmixture of items

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Skill of PerformingScientific Experiments

Activity-I

In the beaker 'A' put some water and ask the children what beaker A contains.In beaker 'B' put some blue ink and ask children what does beaker 'B'contains?Take another beaker 'C' and put the Liquid from A and to C and Liquidfrom 'B' to 'C' and then ask children what the beaker C contains.How many kinds of liquids are present in beaker A B C

Take a beaker 'A', put some water in it and ask children What does it contain?



1. From your real life experience name five different mixtures ofsolid with solid. e.g: sand and saw dust.________________________________________________________________________________________________________________________________________________________________________________________________________

Beaker A (water) Beaker B (ink) Beaker C (solution)

Beaker A (water) Beaker B (sugar) Beaker C (solution)

Beaker C contains more than one type of liquid we call it a mixture ofliquid with liquid.

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Experiments in Science

Take a beaker 'B' put some sugar on it and ask children What does it contain?

Take another beaker; name it as 'C'. Add water from beaker 'A' to 'C' andsugar from disc 'B' to 'C' Ask student to observe and note their observations.

Observation: 1.-----------------------------------------------

2.------------------------------------------------

3. -------------------------------------------------

Ask student how many kinds ofSubstances are there in Beaker A. Beaker B. Beaker C.



1. Name five different mixture involving liquid with liquid________________________________________________________________________________________________________________________________________________________________________________________________________

Beaker C contains more than one type of substance (one solid and oneliq); we call it a mixture of solid with liquid

Take a disc D, put some chalk dust in it and ask children what does it contain.Take another beaker name it as 'E' and put water from beaker 'A' to 'E' andchalk dust from 'D' to beaker 'E'.Ask children to observe and note the observations.

Observation: ------------------------------------------

-------------------------------------------

-------------------------------------------- Chalk dust

Beaker 'E' contains more than one type of substance, one solid and oneliquid. We call it a mixture of solid with liquid

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1.3.2 Methods of Separation of Substances



1. Name five different types of mixture involving solid with liquidand prepare the mixture. e.g.: 1) Water and soil.________________________________________________________________________________________________________________________________________________________________________________________________________

Do you know?

Like mixture of solid with solid, liquid with liquid and solid with liquidmixtures of gas with gas, gas with liquid, gas with solid are also possible.

e.g.: 1) Mixture of N2 and O2.2) Mixture of CO2 and Water.3) Mixture of Coal and Air.

Process of taking out/removing individual substance from a mixture is calledseparation. The common methods of separation are:A) Hand pickingB) ThreshingC) WinnowingD) SievingE) Sedimentation and decantation.F) FiltrationG) Evaporation and condensation

A) Handpicking

Activity 2Let us mix some small pieces of stones with certain quality of sand.Ask 'x' (one student) to separate small pieces of stone from the mixture ofstone & sand. Point out the steps you follow to perform the assignmentsequentially

1 ------------------------------------------ 2------------------------------------------ 3------------------------------------------

On the basis of your experience in the above activity could you tell theconditions for using hand picking method?1. Quantity of impurity is usually small.2. Size of impurity are slightly longer.3. Impurities are visible to unaided eye.

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B Threshing

Activity 3Showing some paddy/stalk (or its figure) to children in the class discuss thefollowing points.

What do you see?Where are the grains attached?Could you count the number of grains attached to the stalk?Could you separate the grains from the stalk?Showing a bunch of stalk to children ask them, could you separate the grains?Could you imagine how a farmer separate such grains from the field?(Discuss and interact with children about the bullock/ or a machine)

Process of picking out larger size impurity from a substance is calledhandpicking



1. From your experiences give some examples of mixture whichcan be separated by handpicking.________________________________________________________________________________________________________________________________________________________________________________________________________



1. From you real life experiences give some example of a mixturethat can be separated by threshing.________________________________________________________________________________________________________________________________________________________________________________________________________

The process of separating the grains from the stalk is called Threshing

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C Winnowing

Activity 4Take a bunch of paddy stable and ask children remove the grains from thestalk and gather the grains at a place over a piece of paper.

Ask student if it is a mixture or a pure substance.What are the impurities in it?Are the components of similar size?Can they be separated by hand picking?

Activity 5

Take some sand and mix it with some saw dust and ask the children abovequestions?How do you separate saw dust from sand?

Demonstrate with following point.1. Take a handful of mixture2. Raise your hand at the height of your shoulder3. Put the mixture on the ground on a piece of paper slowlyWhat do you observe?Observations: -1) Sand and saw dust fall at different placeses2) Saw dust blows away3) Wind plays a major role in separating two components.

Process of separating lighter components from a heavier componentby blowing air is called Winnowing

In the above activity which component is lighter? Which component isheavier?Out of the two which of the two components blows away?

Now, quickly answer the following questions.Conditions for using Winnowing: -1. One of the components (impurities) should be lighter.2. One of the components (impurities) should be heavier3. Role of wind /or blowing air through mechanical means facilitate the

process of separation.



1. Give some examples of mixture which can be separated bywinnowing.________________________________________________________________________________________________________________________________________________________________________________________________________

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Experiments in ScienceD Sieving

Activity 6Collect some sand and a net (sieve) and ask a group of children to separatethe pebbles and stones from it. Showing the substance to children ask themto observe carefully and answer the following questions.

What is the substance called? Do you find any other components present init ?What are they ? Do you call it a mixture or a pure substance ? Could youseparate the impurities (pebbles and stones) from it ? Ask them to carry iton.

Condition for using Sieving

1. Components of the mixture should be very small.2. Components of the mixture are of different sizes.



1. From your real life experience, list some important impurities,which can be separated by sieving.______________________________________________________________________________________________________________________________________________________

E Sedimentation & Decantation

Activity 7Take a glass beaker. Fill three-fourth of it with water. Put a piece of mud init , stir it well and ask children to observe. Demonstrate the activity withthe following steps

� Showing a beaker, ask what this is?� Discuss its physical properties, uses in experiments, etc.� Ask about its measures, size, etc.� Putting water into it, ask what part of the beaker is filled with water?� Instruct a student to contaminate the water by adding some impurities

in the beaker, viz. mud/pebble/sand etc.� Ask children to note down their observation

Observation 1.2.3.

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Stir the beaker with a stirrer and keep it on the table undisturbed. Ask studentsto state their observation.1. Muddy water becomes clean.2. Heavier components are settled at the bottom3. Lighter components (dust) flow at the surface

Process of separating out heavier component from a mixture afteradding water is called sedimentation.

Could you separate the lighter component (dust)from remaining part of mixture now?

Showing the picture, ask the children what do theysee.Demonstrate tilting of beaker to pour out the lighterdust particles from mixture to an empty beaker.

Fig. 1.5: sedimentation process

After removing the dust particles, show the remaining part of the mixtureand ask the following questions to the children.� “What do you see in the beaker?”� “How many layers are there in the beaker?”� “What are they?”� “Do they mix with each other?”� “Could you separate the water from the remaining mixture by

decantation?”

Condition of decantationThrough the process of decantation, always the top layer (lighter particles)can be separated.

Process of filtering the solution/mixture to remove the lighter dustparticles is called decantation.



1. From your real life experience, give example of two mixtures,which can be separated by sedimentation and decantation?______________________________________________________________________________________________________________________________________________________

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Experiments in ScienceF Filtration

Activity 8What does the beaker A contain?What does the beaker B contain?

Could you separate the impuritiesfrom beaker B.How ?

Ask children to conduct theexperiment of sedimentation and collect the clean water in another beaker C.

Ask children to compare water of A with that ofbeaker C.

Why the water in beaker C is not clean like thatof 'A'?

Could you separate all impurities from 'C'?

Activity 9i) Take a filter paper and show it to children.ii) Demonstrate the process of

folding the paper in the shapeof a cone.

iii) Ask children to fit the coneshape filter paper inside thefunnel.

iv) Fit the funnel in a standv) Place a beaker 'D' below the

funnelvi) With the help of a glass rod,

stir the water present in thebeaker C.

vii) Slowly put the water from beaker 'C' to the funnel Through a glassrod

viii) Ask student to observe the water collected in beaker D.ix) Compare the water collected in beaker D with the water present in

beaker A.x) What do you observe inside the funnel?

Beaker 'A' containing Beaker 'B' containing

Fig. 1.6: Beaker A & B containing clean &muddy water respectively

Fig. 1.7: Beaker C containingclean water

Picture showing a glass funnel, a filter paper, afilter paper folded in cone shape, Placing ofcone shaped filter paper over the funnel, andfinally the processes of filtration.

Source: NCERT 2006 Science Textbook class VI

The process of separating the impurities through a filter paper iscalled filtration

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G Evaporation and Condensation

Activity 10Prepare a sugar solution in a beaker. Demonstrate the activity (preparationof sugar solution) in front of children.Ask them the following questions.How many components are there?Could you separate sugar from water?

Evaporation is the process of vaporisation ofliquid which takes place at all temperatures fromthe free surface of the liquid. For example:

o Drying of wet floor by mopping.o Drying of wet clothes by exposing them

to sun.o Application of highly volatile liquid, like

ether, after shave lotions on the body andseeing them to disappear.

Experiment� Take a tripod stand and ask student what this is.� Show a wire gauze and ask student, whether they had ever seen it earlier.� Put wire gauze over it.� Place the beaker containing sugar solution on it.� Heat it to boil by a Bunsen burner/spirit lamp.� Ask student what do they observe

Water starts boiling and starts converting into vapour.



1. Give some example of mixture from your day to day experiencewhich can be separated by filtration?______________________________________________________________________________________________________________________________________________________

Process of Evaporation

Process of conversion of water into vapour is called evaporation. Ittakes place at all temperatures from the free surface of the liquid.

Boiling is a process of vaporisation which takes place at a fixed temperaturefrom the entire body of the liquids

Observation:1) Volume of water decreased2) When all water gets evaporated, show the beaker to the student and

ask what do they see?3) A thin layer sticks to the bottom and the inner side of the beaker?

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Experiments in ScienceWhat is this thin layer?Is it sugar?Where does the evaporatedwater go?Could it be possible to collectthe evaporated water?

Condensation

Activity 11Showing the picture askchildren what do they find overthe beaker?

What is the position of the metallic plate?

What is kept below the edge of the metallic plate?

What is kept over the metallic plate?

Observation

1) Steam (water vapour) coming out from beaker comes in contact withthe lower part of the metallic plate

Picture showing an evaporation of sugar solution, witha metallic plate kept over the container in an inclinedposition, and an empty beaker is placed below the me-tallic plate; a piece of ice is kept over the plate

Source: NCERT 2006 Science Textbook class VI

Process of conversion of water vapour into liquid form is calledcondensation

2) Steam gets converted to water at the lower part of the metallic plate.Why?

3) Condensed water vapour is collected through the edge of the metallicplate in the beaker.



1. Give some examples of mixture from your experience, whichcan be separated by evaporation and condensation.__________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

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1.4 ACIDS AND THEIR IDENTIFICATION

We have already discussed the basic concepts of acid, base and salt in BlockI of Unit I. In this section we shall discuss through tests/experiments aboutvarious properties of acids, bases, and salts.

You are aware about the taste of substances like: lemon juice, vinegar etc.Could you tell how does it taste to you?

Showing a China rose flower, ask children what is it?Have you ever seen the China rose plant in their locality/school?Plucking few petals from the flower, ask children what is this?

Activity 12Ask children to sit in different groups, and provided each group solutions ofthree bakers containing curd, lemon juice and grapes. Each group isprovided with a fresh China rose flower. Ask them to dip a petal in eachbeaker separately and note their observation

Observation� Originally the colour of petal was _____________� Colour of petal after dipping in

o Curd Solution --------------------------o Lemon Juice -----------------------------o Grape Juice------------------------------

� What common feature do you find?� From this, what conclusion could you draw?

o All acidic substances has similar propertieso Without tasting, can you identify acidic substances

1.5 BASES AND THEIR IDENTIFICATION

Have you ever tasted soap?Take a small pinch of it and put in at the tip of your tongue. How does it taste?Is it like that of curd, lemon juice, vinegar?Have you ever tasted baking soda?Take a small pinch of it and put it at the tip of your tongue?Does it have the same taste as curd?Does it have the same taste as soap?

Taste of soap, baking soda are found to be similar and such substancesare called bases

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Experiments in ScienceGive examples of some more substances which are basic in nature (similarto that of baking soda)

1.2.3.4.

Activity 13Ask children to sit in groups and provide each group.Four beakers containing solution of baking soda, soapsolution, lime water and salt solution. Each group isprovided with a fresh China rose flower. Ask them todip a petal in each beaker separately and note their observation.

Observation

� Originally the colour of petal was _____________� Colour of petal after dipping in

o Baking soda Solution--------------------------o Soap solution-----------------------------o Lime water---------------------------------o Salt solution-----------------------------

� What similarities do you find?

There is no change in colour of petal

From this, observation what conclusion could you draw?

All basic substances have similar propertiesWithout tasting, we can identify basic solution

Activity 14Ask children to sit in a group. Give two beakers, one containing acidicsolution and one containing basic solution. Give a China rose flower ineach group. Ask them to identify the solution, which is acidic, and solution,which is basic. Ask them to note their observation in each solution.

Repeat the above experiments taking turmeric powder solution and stateyour observations.Most commonly used natural indicator is litmus paper.

Substances which help in identifying acidic solution from basic solu-tion are called indicators. We can say petals of china rose flower isa natural indicator

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1.6 PHENOLPHTHALEIN AS AN INDICATOR

Activity 15Instruct the students to take three different beakers A, B, C, one containinghydrochloric acid, one sodium hydroxide solution and one phenolphthaleinsolution. Ask students to identify the nature of these three solutions, usinglitmus paper.

Now you label the beaker with stickers as acidic solution, basic solutionand neutral solution. Next you take a test tube, fill one fourth of the testtube with the acidic solution. Ask children what is its colour.

Add few drops (2-3 drops) of neutral solution to it with a dropper and shakegently

Ask children to tell its colour.Do you find any change in colour on adding few drops of neutral solution?Through another dropper, take the basic solution and add a drop of it intothe test tube. Shake gently.

Do you find any change in colour?Repeat the same adding a drop of basic solution and ask same questions tochildren in each step about change in colour.At one point there is a sudden change of colour from colourless to pink.Add one drop of Acidic solution to the pink colour solution and ask childrenthe following:� What do they observe?� For change in colour of solution from pink to colourless, Who is

responsible for it? (Acidic solution)� Now add one drop of basic solution to the colourless solution and ask

children, what they observe.� Change in colour of solution from colourless to pink

Who is responsible for changing the colour from colourless to pink?(Basic Solution)

What conclusion can be drawn from this experiment?

When the solution is basic, pink colour appears.When the solution is acidic, pink colour disappear (colourless solutionappear)

What is responsible for the change in colour (appearance and disappearanceof colour?)Which substance/Nature of solution is governing this change within thesolution?

Phenolphthalein is the substance present in the solution which is causingthe colour change. When the solution was acidic, addition of phenolphthaleindid not bring about any colour change and the solution remained colourless.However when a basic solution was added the colour changed to pink.

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Experiments in ScienceThus phenolphthalein gives pink colour with a base and remains colourlesson addition of acid.

Hence phenolphthalein is an indicator.



1. Repeat the above experiments(i) Taking blue litmus paper for all acidic solution and state

your observation.(ii) Taking red litmus paper for all basic solution and state your

observation.________________________________________________________________________________________________________________________________________________________________________________________________________

1.6.1 Characteristics of Neutralization Reaction

Activity 16Take five beakers A, B, C, D and E.Fill one fourth of each beaker nearly (100 ml) with sodium hydroxidesolution.In A, B, C, D, E add 10 ml, 20 ml, 30 ml, 40 ml and 50 ml of HCl respectively.In each beaker, dip a red litmus paper and observe the changes in colourseparately

ObservationIn all cases red litmus turns to blueDo you find any change in intensity of blue colours in each case.� There is a change in intensity of blue from A to E� In A intensity of blue is high.� In E intensity of blue is leastWhy there is variation in intensity of blue colour?

In A intensity of blue was high. Could you tell the reason?(Volume of HCl was least, Basic properties were highest)In E intensity of blue was least. Could you tell the reason?(Volume of HCl was highest, basic properties were least).What general conclusion can be drawn?

On increase of volume of acid in basic solution, gradually basic propertybecomes less and less effective and acidic properties dominate.

Due to change in volume of HCl

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This process is called neutralization.

The reaction that occurs inside the solution is called neutralization reaction.

Activity 17You will perform this activity with the help of students.Let us keep the beaker A on your left palm and beaker E on your right palm.What do you feel? Why do you feel hot?Reaction between acid and base produces heat.In which palm you feel hotter?In the right palm.Why do you feel hotter at your right palm?From Beaker E more heat is liberated.Amount of heat liberated depends on which factor?It depends on the extent of reaction between Acid and Base.Take the beaker E and heat it to drynessWhat do you observe at the end?Solid crust is deposited at the bottom and side of the test tube.Could you tell what this solid crust is?The solid crust is salt. How does this salt formed?It is formed by a reaction between acid and base.

Acid +Base = Salt + WaterHCl + NaOH = NaCl + H

2O

Reaction between acid and base to produce salt and water with theliberation of heat is called neutralization

What are the products formed in a neutralization reaction?Salt and water

The characteristics of a Neutralization Reaction are:

� Acid reacts with a base or vice versa.� Heat is evolved during the reaction.� Salt and water are produced.

1.7 PROPERTIES OF METALS AND NON-METALS

Concept of metal and its characteristics (physical properties) have beendiscussed in Block 1 of Unit I. In this section, we will discuss about teachingstrategies or chemical properties of metal and non-metals and someexperiments related to it.

1.7.1 Reaction with Air (Oxygen)

Given below are the chemical reactions of some common metal like Fe,Mg, Cu, Al, Zn etc with oxygen4Fe + 3O

2= 2Fe

2O

3

2Mg+ O2

= 2MgO

Metals react with air (O2) to

form their respective oxide

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Experiments in Science2Cu+ O2

= 2CuO4Al+ 3O

2= 2Al

2O

3

2Zn+ O2

= 2ZnO

Activity 18Take 5 different beakers, label them as A, B, C, D and E.Take 50 ml, of water and put a pinch of Fe

2O

3, MgO, CuO, Al

2O

3 and ZnO

in A, B, C, D and E respectively.With the help of a litmus solution, test the nature of each substance andstate your observation.

Oxides of metal are basic in nature

1.7.2 Reaction with water

Activity 19Take three different beakers Labels them as A, B, C and fill 3/4th of eachbeaker with water. Put small pieces of Na, Mg and Pb in A, B and Crespectively.Ask children to state their observation.

Na reacts vigorously and violently with water in beaker A.

Reaction of Mg and Pb in B & C are respectively very slow.

Na reacts faster with water whereas reaction of other metal with wateris very slow

After the reaction ceases, Ask the children to touch three beakers, one byone and state their observations.

Beaker A becomes very hot.In beakers B & C change is not noticeable

Huge heat is liberated when Na reacts with water

Non metals do not react with water

1.7.3 Reaction with Acids

Activity 20Take different test tubes; label them as A, B, C & D.Fill 1/4 of each test tube with dilute HCl.Put a small piece of Mg, Al, Fe and Cu to A, B, C & D respectively.Observe carefully and read your observation for each test tube.

ObservationTest Tube A------------------------------------

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Test Tube B------------------------------------Test Tube C-----------------------------------Test Tube D-----------------------------------On the basis of your observation, where there is no reaction, heat the testtube gently and record your observation



1. Write the chemical reactions for each of the above experiment

(i)Reaction for A_________________________________________

(ii)Reaction for B ________________________________________

(iii)Reaction for C _______________________________________

(iv)Reaction for D _______________________________________

Similarly, the activity can be performed taking H2SO4 or HNO3 in placeof HCl

1.7.4 Reaction with Bases

Activity 21Performed by childrenProvide some NaOH pellets in a disc, water in a beaker, few Al foils in adisc and a test tube.Ask children to prepare a solution of NaOH with 10 ml of water and writethe steps of preparation.

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Performed by TeacherNow hold the test tube containing NaOH solution in a test tube holder, puta small piece of Al foil into it and ask children to note what they observe1.23In the next phase, take a burring match stick, put a small piece of Al foilinto the test tube and show the burning match stick near the mouth of thetest tube and ask children to state their observation.

1.7.5 Reaction with Salt solution

Activity 22Take three beakers. Label them as A, B, C,

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Experiments in ScienceTake CuSO4, ZnSO

4, and FeSO

4 in three different discs

Ask children to prepare CuSO4 solution, ZnSO

4 solution and FeSO

4 solution

separately with 50 ml of water in each beaker.

Showing beaker A ask children to observe the colourand ask them to put a piece of Zn granule to it.

State their observation1. Solution becomes colourless2. Reddish brown substance deposited

On the basis of the change of colour, ask them why there is a change incolour.Let us write the equations for the above reactions.

CuSO4 + Zn = ZnSO

4 + Cu

What conclusions can be drawn?Zn can displace Cu from CuSO

4.

So out of Zn & Cu, which is more reactive?



1. Taking CuSO4 solution and Fe granules, demonstrate the

experiment and show that Fe is more reactive than Cu. And stateyour observation________________________________________________________________________________________________________________________________________________________________________________________________________

2. Perform the experiment taking ZnSO4 and Fe and state yourobservation and draw conclusion.________________________________________________________________________________________________________________________________________________________________________________________________________

1.8 LET US SUM UP

In this unit you learnt that:

� Scientific experiments pertaining to separation of substances,� Strategies for performing experiments related to reactions of acid, bases,

and salts

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� Skill of performing experiments related to properties of metals andnon-metals.


Answer 11. Salt and Salt:

(i) Masoor Daal + Matar Daal(ii) Rice + impurities like small pieces of stone(iii) Gulal of two different colurs(iv) Milk powder + coffee powder

Answer 21. Water and Lemon juice

(i) Vinegar and Water(ii) HCl and Water(iii) NaOh and Water(iv) Nail Polish and thinner

Answer 31. Salt and Water

(i) Sugar and Water(ii) Milk and Sugar(iii) Tea leaves and Water(iv) Sulphur and Benzene

Answer 41.

Stones from rice grainPebbles from sandPeas from rice pulao

Answer 51.

Threshing of black gram with sticks

Answer 61.

Skin from roasted peanutsRice grain from chaffImpurities from puffed rice (poha)

Answer 71.

Impurities from wheat grainImpurities from semolinaTea leaves from tea solution

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Experiments in ScienceAnswer 8Sand and WaterJaljeera powder and waters

Answer 91. Mixture of sand and salt solution. Sand remains on filter

paper and salt solution comes in beaker.Jaljeera water solution.

Answer 101.

Salt and waterSugar and waterAlcohol and Water

Answer 12

(i) Reaction for A: Mg + 2HCl MgCl2 + H

2

(ii) Reaction for B: 2Al + 6HCl 2AlCl3 + 2H

2

(iii) Reaction for C: 2Fe + 6HCl 2FeCl3 + 3H

2

(iv) Reaction for D: Cu + 2HCl CuCl2 + H

2

1.10 GLOSSARY

Mixture Substance containing two or more substances, not ina fixed proportion

Hand-picking Process of picking out large size impurities form asubstance

Threshing Process of separating grains from stalk

Winnowing Process of separating lighter components from aheavier component by blowing air.

Sieving Process of separating impurities from a substanceusing a net/sieve

Sedimentation Process of separating out heavier component from amixture after water is added to it

Decantation Process of filtering the solution/mixture to remove thelighter particles

Filtration Process of separation of impurities using filter paper

Evaporation Process of conversion of water to water vapour

Condensation Conversion of water vapour to liquid form

Neutralization The reaction between an acid and base to form saltand water is called neutralization and heat is produced

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1.11 REFERENCES

IGNOU (1999), Teaching of Science, Indira Gandhi National OpenUniversity.

NCERT (2007), Science text Book for Class VI, National Council forEducational Research and Training, New Delhi.

NCERT (2007), Science text Book for Class VII, National Council forEducational Research and Training, New Delhi.

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UNIT 2 RESPIRATION, FOOD ADULTERATION, TRANSPIRATIONAND USE OF MICROSCOPE

Structure

2.1 Introduction2.2 Objectives2.3 Need for Transport System

2.3.1 Transportation of Minerals in Plants2.3.2 Transportation of Food in Plants

2.4 Uses of Microscope2.4.1 Simple Microscope2.4.2 Compound Microscope2.4.3 Using a Simple Microscope2.4.4 Dissecting Microscope

2.5 Respiration2.5.1 Breathing2.5.2 Internal Respiration2.5.3 Respiration and Gaseous Exchange in Plants2.5.4 Respiration and Gaseous Exchange in Animals

2.6 Adulteration of Food materials2.7 Let Us Sum Up2.8 Answers to Check Your Progress2.9 Glossary

2.1 INTRODUCTION

In order to survive, organisms require oxygen, water and food. They needcertain other substances to carry out various life processes. Oxygen, water,food and other substances may be procured at one end of the body of anorganism and transported to other parts.

Chemical reactions that take place in the body cells produce wastes. Thesewastes include carbon-di-oxide and urea. These chemical wastes have to beremoved; otherwise they would poison us.

2.2 OBJECTIVES

After reading this unit you will be able to� explain the process of transportation of useful materials and waste

materials from one part of the body to another in plants and animals.� describe the processes of transpiration and excretion of living organisms.� list out the uses of transpiration in plants.

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� distinguish between various types of transportation in plants andanimals.

2.3 NEED FOR TRANSPORT SYSTEM

In order to live, all living cells need to obtain oxygen and food from theenvironment. At the same time, wastes produced by the cells have to beremoved; otherwise these can poison and kill the cells. But how do livingorganisms obtain important materials from their surrounding and removewaste products?

For every small organism such as the Amoeba or the Bread mould, theirbody surface is in close contact with the surrounding. This allows food andoxygen to enter the cells directly. In the same way, waste products diffusedirectly from the body surface to surroundings. Hence, we can say that thetransport of materials in small organisms occurs by diffusion. Advancedorganisms like human beings and trees are made up of millions of cells.Most of their cells are not in direct contact with the surrounding. As diffusionis a slow process, it will take a long time for required substances to diffusefrom one cell to another. Large organisms, therefore, need an efficienttransport system to carry oxygen, water, digested food and waste products.

2.3.1 Transportation of Minerals in Plants

Activity 1� Ask the students to cut three leafy shoots from a tree or shrub that

sheds leaves annually (deciduous plants). Each shoot should have aboutthe same number of leaves.

� From one twig tell them to remove a ring of bark about 5 mm wide and100 mm up from the cut base.

� With the second shoot, instruct them to smear a layer of Vaseline overthe cut base so that it blocks the vessels.

� Inform them that the third twig is a control.� Next ask them to place all three twigs in a jar with a little water. Instruct

them to keep the water level below the region from which they removedthe ring of bark.

� Leave the things where they can receive direct sunlight.

What will you observe?

After an hour or two, you will probably find that the twig with blockedvessels shows signs of wilting. The other two twigs should still have goodleaves.

Thus, it can be said that removal of the bark (including the phloem) has notprevented water from reaching the leaves, but blocking the xylem vesselshas. The vessels of xylem, therefore, are often the most likely route forwater passing up the stem and work as drain pipe in the stem.

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Respiration, FoodAdulteration, Transpiration

and Use of Microscope

The xylem vessel is a non-living, long tube which runs like a drain pipethrough the plant. The vessel is made of many hollow, dead cells, joinedend to end. The end walls of these cells have broken down so that the plantright up through the stem and reach the leaves. The xylem vessels branchinto every leaf of the plant.

Transportation of water, minerals and food in plants is done by special tissuespresent in the root, stem and petioles (or the stalk) of the leaves. Thesespecial tissues are called the vascular tissues. The term vascular in Latinrefers to tubes and vessels that transport liquids.

Soil is the reservoir of water and minerals for the plants. Water and dissolvedminerals are absorbed from the soil by root hair of the roots of the plant.These are then transported upwards to different parts of the plant (stem,leaves and flowers) through xylem tissues. Similarly, manufactured food inthe leaves in the form of sugar (glucose) is transported to different partsthrough phloem tissue. The xylem and phloem tissues together constitutethe vascular bundle.

Plants absorb water by their root hair present in young roots. Orchids growingover trees have hanging roots. These roots absorb water from the atmosphere.These plants grow non-parasitically upon another, deriving its nutrients andwater from rain, air, dust etc. Such plants are called epiphytes.

Plants require water for producing food by the process of photosynthesisand to keep the cells turgid. Plants also need mineral salts like nitrates,phosphates, etc. for various processes. Water and minerals are absorbedfrom the soil by roots and transported to various parts of the plant, likestem, leaves and flowers. Water absorbed from the soil moves to the leavesthrough xylem tissues and carbon di-oxide entered from the atmosphereare used up. Constant diffusion of water alone with the minerals from theroot cells produces a pushing force. Simultaneously, water constantly getsevaporated from the leaves of a plant in the form water vapour. This processis called transpiration. This loss of water creates a pulling force, transpirationpull which causes more water to enter the roots and it is simply pulled upvia the water conducting tissue, xylem. The process is similar to whathappens when you suck water up a straw.

2.3.2 Transportation of Food in Plants

As you know, leaves prepare food by the process of photosynthesis. Thefood made by leaves is in the form of a simple sugar. The food manufacturedby the leaves of a plant is transported to its other parts through a kind oftube system of the phloem cells. The transportation of food from the leavesto the other parts of the plant is called translocation. The movement ofmaterials through phloem depends on action of living cells called sievetubes.

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Food molecules enter the phloem cells from the food producing cells of theleaf. Once they enter phloem, they can be transported either upwards ordownwards to all parts of the plants, including roots. Translocation isnecessary as every part of the plant needs food for harnessing energy andfor building and maintaining the organism.

Green leaves of plants manufacture glucose as their food material. This istransported to the different parts of the plants in the form of a solution.Transportation occurs mainly through the sieve tubes of the phloem fromthe root tips to the stem tips through which dissolved food substance movefreely.

Let us do 'Ascent of Sap' experiment. Let us put a Balsam plant in redsolution and observe the veins of the leaf after sometime. You can see astreak of red veins on the leaf. If you take a cross section of the leaf or stemand observe, you can see that the xylem and phloem get red colours. Thisshows that water and food (minerals) get conducted through xylem andphloem.



1. List out the uses of transpiration.______________________________________________________________________________________________________________________________________________________

2. What is the difference between evaporation and transpiration inplant?______________________________________________________________________________________________________________________________________________________

In the next section you will read about an important instrument, used in ascience laboratory, i.e., the microscope.

2.4 USES OF MICROSCOPE

Activity 2You will help the students to study the parts of a microscope and its properuse.

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RequirementsFor this you will need a compound microscope and a prepared slide(permanent slide).

ProcedureYou will take a microscope and acquaint the students with its various partsbefore they begin using it.The body of the microscope is an ocular lens (eye piece) which can bechanged for lower or higher values of magnification. At the lower end ofthis tube is revolving nose piece with three objective lenses. The tube of themicroscope is vertically movable with the help of coarse and fine adjustmentscrews on the limb.

Now you will instruct the students to use the microscope.Place the prepared slide on glass slide on the stage under objective piecealmost in the middle of the microscope. Adjust the light with the help of themirror (reflection) and condenser so that it passes through the specimen. Amagnified image of the object can be seen from the eye piece after focusingit with the side knobs (adjustments). The magnification of image can beincreased further by changing the objectives with high power.

Precautions� Place the microscope in diffuse light as direct light is harmful to the

eyes.� Use coarse adjustment for focusing the object under low power and

use fine adjustment for the high power objective.� Always observe with both eyes open.� Do not swing the microscope with one hand. Always handle the microscope

by keeping one hand at the base and the other holding the arm.� Keep the microscope in upright position while carrying from one place

to other.� Never lower the body tube while liking through the eye piece. By doing

so one may unknowingly ram the objective into the slide. This maybreak the slide and damage the objective.

� For natural daylight use plane mirror and for artificial light the concavemirror.

� While looking through eye piece, do not close the other eye. This willproduce eye strain. With a little practice, it becomes easier to keepopen the eye that does not look through the eye piece.

� Do not touch lenses or mirror with your fingers.� Clean the lenses and the mirror with the help of tissue paper / lens

paper. Always locate the objects with the help of low-power objective;one then use the high power objective for finer details of the object.

2. Observing Onion Cells

Materials requiredA small onion, watch glass, slide, cover slip, ethylene blue stain, glycerine,blotting paper and microscope.

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ProcedureCut a small part of onion and separate a peel from one of its inner layers.Place the peel on a glass slide in drop water. Put a drop of methylene blueon the peel. Wash it in water to remove the excess stain. Put a drop ofglycerine and cover it with cover slip. Observe it under low and high powersof microscope.

To prepare a temporary mount of the onion peel and study theplant cell

ConceptA plant cell possesses most of the components of an animal cell. Additionally,it has a cell wall, Chloroplasts and a large vacuole. However, some of thestructure may be lacking in some plant cells. For example, non photo-synthesizing cells may not have green pigmented chloroplasts. The largevacuoles are found only in mature plant cells.

ObservationElongated and roughly rectangular cells arranged in a brick like fashioncan be observed. Each cell has a rigid cell wall outside the plasma membraneand deeply coloured rounded nucleus, surrounded by granular cytoplasm.The central part of the cell is occupied by the central vacuole.

Precautions� Avoid the folding of the peel.� Extra stain should be blot of with blotting paper before putting a cover

slip.� The entry of bubbles should be avoided while putting a cover slip.

Cells are tiny structures, which can be seen only with the help of microscope.Microscope is an optical instrument, which magnifies small objects seenthrough it. A compound microscope which is commonly used in thelaboratory can magnify a cell up 2000 times. The fine details of differentcell organelles can be visualized through an electron microscope. Itmagnifies an object as much as a half million times.

CHECK YOUR PROGRESS 2Note: : Perform the given exercises.

1. Check whether you can mount a permanent slide on the field ofthe microscope and focus it to see the slide.

2. Check whether you can prepare a slide of plant cell with onionpeeling.

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Microscope is a costly and sensitive instrument. It is used to observe things,living/ dead organism, cells and tissues which cannot be seen by the nakedeyes or even with the help of hand lens.

Magnifying lens is used to see objects like butterfly, small flower etc. Simplemicroscope/dissection microscope is used to see cut section of ovaries of aflower or seed etc. Compound microscope is used to see microorganisms,organelles of cell etc.

2.4.1 Simple Microscope

The simplest type of microscope has a single lens system. It is based on theprinciple that when an object is placed between a convex lens and its principalfocus, an enlarged virtual image is formed. The brain can, therefore,distinguish more details.

The simple microscope consists of a double convex or biconvex lensmounted on a handle. Ordinarily, it magnified things up to 4-5 times,depending upon magnifying power of the lens (3X, 4X, 5X, etc.). It is calledmagnifying glass or a hand lens or a reading glass (See Fig.7)

It has a single lens mounted on a vertical stand through a folded arm, amoveable arrangement for focusing, a reflecting mirror and a glass stage.The magnification of this microscope (usually called dissection microscope)ranges from 5 to 50 times depending upon the magnification of the lens.

The dissection microscope is used to observe whole mounts of smallorganisms such as mosquito, to study parts of a small flower, to observesmall organs or parts of an animal while performing a dissection (locatingovary of earthworm at the time of dissection).

Fig 3.1: Simple Microscope (Dissection Microscope)

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2.4.2 Compound Microscope

A compound microscope consists basically of two systems of lenses, calledthe objective and the ocular (eye piece). The term microscope is in practiceapplied only to the compound microscope. In this microscope, the object tobe examined is placed in front of the objective which forms a magnifiedimage. That is picked up, further magnified and made visible to the eye bythe eye piece.

Magnification power of a compound microscope is given by:M = Magnification power of eye piece lens x power of objective lens

Magnification power of objective lens and eye piece lens is expressed bythe symbol X. It denotes number of times a lens magnifies an object.Generally, a compound microscope consists of eye lens of 10X or 15Xmagnification. The objective lens of 10X (low power) and 45X (high power)magnification. Thus, for low power magnification of compound microscope

M (LP) = Power of eye piece x power of objectiveM (LP) = 10X x 10X = 100X

It means that under low power of a microscope having 10X eye piece and10X objective, an object can be seen 100 times bigger than its original size.

Similarly for high powerM

(HP) = 10X x 45X = 450

That is, under high power (H.P) an object can be seen as magnified as 450times of its size.

Structural Parts of Compound Microscope1. Base or Foot: It is a metallic horse-shoe shaped structure. It provides

stability to the microscope and supports other parts.2. Limb or Pillar: It is fixed with a hinge to the foot.3. Arm. It is curved and supports the body tube and coarse adjustment.4. Inclination Joint: The joint where the arm is attached to the pillar is

known as inclination joint. It permits tilting of the microscope to adjustto eye level.

5. Stage: It is rectangular flat metallic plate, fixed to the lower end of thearm. It has an opening in the centre for admitting light to illuminate theobject. Two clips are provided over it to hold the slide.

6. Diaphragm: It is present below the stage of the microscope for regulatingthe amount of light. Diaphragm may be disc diaphragm or iris diaphragmtype.

7. Body tube: The body tube is a hollow tube and is vertically mountedover the stage, attached to the upper part of the arm. It can be moved upand down with the help of the screw. The body tube consists of(a) Eye piece at the upper and fitted in its hollow tube. The eye piece

is replaceable. It can be of 10X or 15 X magnifications, replacedaccording to need.

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(b) The circular metallic attached at the lower end of the hollow bodytube is called nose piece. Generally, it has three openings in whichobjectives of different magnification can be fitted.

(c) Objective tenses. Each objective lens is fitted in a metallic holderwhich can be fixed with the help of screws in one of the holes of thenose piece. Generally, objectives with magnification power 10X (lowpower) and 45% (High power) are available in students' compoundmicroscope. In research/demonstration compound microscope, thereis provision of a third objective with 100X magnification.

8. Coarse adjustment screw: The screw which can move the body tube upand down for coarse focusing the object is known as coarse adjustmentscrew.

9. Fine adjustment screw: The screw which can move the body tube veryslowly to achieve fine and sharp focus is known as fine adjustmentscrew.

10. Condenser: In some compound microscopes, a third system of lenses.The substage condenser is found. It is located beneath the stage of themicroscope. It concentrates light on the object from a wide angle.However, it is not essential.

11. Mirror: It is attached at the lower end of the arm, below the stage. It isconcave on the side and plane at the other side. It reflects light throughthe aperture/hole of the stage to the specimen slide.

Setting a compound Microscope(a) Place the microscope gently on a working table keeping the arms towards

you. The base should be at least six inches inside the edge of the table.(b) Clean the lenses of the microscope with lens paper or tissue paper or a

piece of silk cloth.(c) Using the coarse adjustment raise the body tube an inch or so above the

stage.(d) Rotate the nose piece until the low power objective (10X) is in line

with the body tube and clicks into position. Do not stop before the clickis heard and do not rotate after the click. You should stick to it evenwhen changing one objective to another.

(e) Open the diaphragm of the condenser carefully.(f) Look through the eye piece with one eye. Hold the edge of the mirror

below the stage with the thumb and forefinger of both hands. Tilt andturn the mirror towards a light source (Window or door) and reflect thelight vertically up. When the mirror is in proper position, the circularfield in the microscope will be illuminated. Carefully tilt the mirror andadjust the position so as to make the field uniformly illuminated. Donot let direct sunlight strike the mirror.

Focusing of the Microscope1. Turn the low power objective of the microscope into position (The low

power objective is shorter in length than the high power one).2. Place the slide of section of dicot stem on the microscope stage so that

the specimen / section of stem is directly below the objective.

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3. While looking at the microscope from one slide, use the coarseadjustment and lower the body tube until the distance between theobjective and the cover glass is about I mm.

4. Look through the ocular with one eye, keeping the other eye open.Use the coarse adjustment and raise the body tube slowly until thestructure of section of stem comes into a clear view. Now, use the fineadjustment and focus the image sharp.

5. Compare the structure of the section of dicot stem as seen underdissecting microscope with that seen under compound microscope.

Use of the High Power ObjectiveIt is used when more magnification or details of a small portion of tissue orany other objective is needed.

(i) After view through low power, turn the high power objective till itclicks into position.

(ii) Look from the slide and move the body tube down with the coarseadjustment carefully until the objective almost touches the cover glass.

(iii) Now look through the ocular and slowly raise the body tube usingthe fine adjustment until the image of the object comes into view.Focus sharp.

(iv) Adjust the diaphragm for correct illumination.Is the area of the object visible, the same as under low power?Are details of the object cleaner than the low power?

2.4.3 Using A Simple Microscope (Hand Lens)

(i) Take a hand lens and study its structural parts. Draw diagram of itsparts and label them.

(ii) Take a plain sheet of paper. Draw a ½ cm long line on it with the helpof a pencil or ink pen. Now, observe this line with one eye through ahand lens and draw a second line nearby it with the help of yourunaided eye on the basis of image you see through lens.

Do you find any difference between the lengths of the two lines? Measurethe second line and record your observation.

(iii) Examine the permanent slides of whole mount of mosquito and asection of dicotyledonous stem or an epithelial cell slide with thehelp of a hand lens. Record your observations.

2.4.4. Dissecting Microscope

Structural Parts and their Utility

1. Base: It is metallic, heavy and forked. It supports other parts of thedissecting microscope

2. Stand: It is a short, hollow, cylindrical metallic rod. It is fixed at oneend with the base. It is used for holding the dissecting microscope.

3. Vertical limb: The vertical limb is a short hollow cylindrical rod whichfits into the hollow tube of the stand. It can be moved up and down

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with the help of adjustment screw to help in focusing an object.4. Folded arm: The horizontal flat arm attached to the end of the vertical

limb is known as folded arm. The folded arm has a lens fitted at theother end. This arm can be moved side ways, up and down for focusingan object. The lens fitted in the folded arm may be of 5X, 10X or 20X.

5. Stage: It is a rectangular glass plateattached with upper end of the stand.It is supplied with two clips. The stageserves the purpose of placingspecimen or slide. There are two clipswhich hold the object in its place.

6. Mirror: At the lower end of the stand,a concave mirror is attached. It helpsin reflecting light at the stage toilluminate the object.

Setting and working of the dissectionMicroscope1. Take a dissection microscope, cleanits stage and lens with the help of the lenspaper. Place a slide of whole mount of

mosquito on the stage. Adjust the light with the help of the mirror sothat the object gets illuminated wit the help of reflected light. Now,bring the lens over the object with the help of the folded arm. Focus theobject by moving lens up and down with the help of the adjustmentscrew.After examining the slide under the dissection microscope, observe itthrough unaided eyes. Do you find any difference?

2. Take a small flower such as candytuff, verbena, etc. and observe itsparts with unaided eyes. Then under the dissecting microscope, whatdifference do you find?

3. Observe the slide of section of dicot stem under the dissectingmicroscope. Are you able to difference different types of cells clearly?

Precautions1. Do not swing the dissecting microscope with one hand while carrying.

The lens is loosely fitted, it may fall down. Always keep the dissectingmicroscope in upright position by holding it with both the hands.

2. Do not put fingers over the lens or mirror. The impression of the fingersdistorts the image.

3. Always clean the lens or mirror with the lens paper or a clean piece ofsilken cloth.

4. Keep the stage of the dissecting microscope clean.5. Do not move the lens too low to touch the object or water while using

the microscope in dissection for locating small organs such as ovariesof earthworm.

6. Always replace the dissection microscope in its box after use.

Fig 3.2: Compound Microscope

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2.5 RESPIRATION

The process that involves intake of O2 and release of CO2 and energy fromfood is called respiration. Respiration is sometimes called cellularrespiration, internal respiration or tissue respiration. It is the process inwhich food is broken down in body cells through various chemical reactionsin the presence of oxygen to give out carbon dioxide along with water andenergy.

C6H

12O

6 + 6O

26CO

2 + 6H

2O + Energy

Glucose Oxygen Carbon Waterdioxide

The process of respiration shown above is common to all the livingorganisms, both plants and animals. It consists of three phases: diffusion ofoxygen into the cells, oxidation of food in the cells to produce CO

2 and

H2O and elimination of CO

2 from the cells.

An interesting observation made for the process of respiration is that itseems quite similar to the process of burning or combustion. This is becauseof the fact during respiration food is oxidized or burnt as a fuel to produceenergy.

2.5.1 Breathing

The process in which, oxygen is taken inside the body and carbon dioxideis given out is called breathing or external respiration. Thus, breathinginvolves only a simple exchange of gases. Different animals breathedifferently. In Amoeba, the exchange of gases occurs through its entirebody surface. Fishes breathe through their special organ called the gill. Inearthworms and leeches, the exchange of gases takes place through theirmoist and slimy skin which acts as on organ for respiration. In frogs too,the breathing is conducted through the skin. Insects breathe with the helpof air tubes called trachea. Reptiles, birds and mammals breathe throughtheir organs called lungs. In plants breathing takes place through pores calledstomata present in the leaves.

During breathing taking in of air rich in oxygen is called inspiration whilethe giving out of air rich in carbon dioxide is called expiration.


1. Mount a permanent slide on the field of the microscope and focusit to see the slide.

2. Prepare a slide of plant cell with onion peel.

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Characteristics of Breathing

� It is a physical process involving exchange of O2 and CO

2.

� There is no release of energy.� Enzymes are not involved.� Modes of breathing are different in different organisms.

Characteristics of the process Respiration

� Occurs at normal body temperature.� Takes place in living cells.� Various enzymes facilitate this process.� Many steps are involved in the breakdown of food (which acts as fuel)

to finally produce energy and let out carbon dioxide and water asbyproducts.

� Energy produced by this process is in the form of a complex moleculecalled ATP.

� Respiration is a slow process of energy release.

2.5.2 Internal Respiration

Depending upon the utilization of O2, respiration is of two types

Aerobic respiration

The word aerobic means that oxygen is needed for this chemical reaction. Inthis process the food molecules are combined with oxygen and get oxidizedinside cell. These food molecules are then broken down into carbon dioxideand water and then energy is released. All food molecules contain carbon,hydrogen, and oxygen atoms. The process of oxidation converts the carbonto carbon dioxide (CO

2) and the hydrogen to water (H

2O). At the same time

this process sets free energy which the cells can use to drive other reactions.Aerobic respiration can be summed up by the following equation:

C6H12O6 + 6O2 6CO2 + 6H2O + Energy

Glucose Oxygen Carbon Waterdioxide

Although the energy thus produced is used for variety of processes, someof it always appears as heat. In 'warm-blooded' animals (birds and mammals)some of the heat released retained to keep up their body temperature. Incold blooded animals (reptiles and fish) the heat may build up for a timeand allow the animals to move about faster. In plants the heat is lost to thesurroundings as fast as it is produced.

Anaerobic respiration

The word anaerobic means 'in the absence of oxygen'. In this process energyis still released from food by breaking it down chemically but the reactions

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do not use oxygen though they often produce carbon dioxide. A commonexample of anaerobic respiration is the action of yeast on sugar solution.The sugar is not completely oxidized to carbondioxide and water butconverted to carbon dioxide and ethyl alcohol. This process is calledfermentation and is shown by the following equation

C6H

120

62C

2H

5OH + 2CO

2+ Energy

Glucose Ethyl alcohol + Carbon dioxide

The process is of brewing (to make fermented alcoholic beverages) andbread-making rely on anaerobic respiration by yeast. The anaerobicrespiration takes place in small steps and needs several different enzymes.The energy produced by anaerobic respiration is much less than thatproduced through aerobic respiration. Besides yeast, certain types of bacteriaand some body tissues also respire an aerobically.

Characteristics of Aerobic Respiration

� It occurs in all living organisms � Oxygen is required for this type respiration. � Complete oxidation of food occurs during the process

2.5.3 Respiration and Gaseous Exchange in PlantsPlants do not have special breathing organs. However, they do respire.

Let us do the following activity to prove that plants respire.

Activity 4Put some germinating wheat grains in a large test tube. Cover the mouth ofthe tube with aluminium foil. After 15-20 minutes, take a sample of the airfrom the test tube. Do this by pushing a glass tube attached to a 10 cm3plastic syringe through the foil and into the test tube. Withdraw the syringeplunger enough to fill the syringe with air from the test-tube. Now slowlybubble this air sample through a little clear lime water in a small test tube.Cover the mouth of the small test tube and shake the lime water up.

Result:The lime water turns milky.

Interpretation:

Lime water turning milky provides evidence of carbon dioxide but it couldbe argued that the carbon dioxide came from the air or that the seeds giveoff carbon dioxide whether or not they are respiring.

2.5.4 Respiration and Gaseous Exchange in Animals

We know that animals obtain energy from food they eat. Before the energycan be used by the cells of body, it must be set free from the chemicals of

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the food by respiration. We have seen that aerobic respiration needs a supplyof oxygen to breakdown the food which releases needs a supply of oxygento breakdown the food which releases energy. During respiration animalcells produce carbon-dioxide as a waste product. All cells, therefore, mustbe supplied with oxygen and must be able to get rid of carbon dioxide. Letus study how gaseous exchange during respiration takes place in differentanimals.

EarthwormThe earthworm inhabits burrows in damp soil, and emerges to feed in thedarkness. Gaseous exchange occurs through its skin. In earthworm, the thin,moist skin is supplied with a network of capillaries (tiny blood vessels)which absorb oxygen from the atmosphere and deliver it, to the rest of thebody. The absorbing surface or the network of capillaries also gets rid ofcarbon-dioxide from the body.


� Perform the experiment with respiroscope� Collect information abut the respiration in man

2.6 ADULTERATION OF FOOD MATERIALS

Adulteration means mixing undesirable or unwanted materials in food items.The disadvantages of adulteration to the consumers are� Paying more money for a food stuff of poor quality and� Some adulterants are very harm to health and even result in death. For

example, adulteration of mustard oil with Argemone oil causes "dropsy"epidemic

Table 3.1: Common Adulterants in Food Stuffs

S. Food Adulterant Food AdulterantNo Material Materials1. Cereals wheat, Mud, Grit, Soap Dania Powdered cow -

rice etc.) tone Powder dung andhorse-dung

2. Haldi (turmeric Lead Chromate Mustard ArgemonePowder) seeds seeds

3. Dal Kesar Edible Oil Cheaper OilsE.g. mineral orArgemone oils.

4. Black pepper Dried papaya Milk Addition ofseeds starch,

extraction of fat.5. Chilly powder Saw dust, brick Honey Jaggery. Sugar

powder

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Activity 5To test the presence of the adulterant metanil yellow in dal.

Materials RequiredSample of dal, hydrochloric acid, test tube.

ProcedureCollect 5- 10 g of of yellow dal (Arhar dal) and proceed as given in table.

Procedure Experiment Observation Inference

Take 5 G. of Arhar Contains metanil(yellow) Dal of water in it A pink colour yellow (a dye) in aand shake well. Now, add appears test tube. Put 5 mla few drops of HCI in the of which is antest tube. adulterants

ResultIn yellow coloured dal such as in Arhar metanil yellow dye is used ascolouring material. Metanil yellow is an adulterant.

Precautions1. Use chemicals/reagents judiciously.2. Keep the mouth of the test - tube away from your face and other clothes

while beating the reactants.3. Always use test-tube holder while heating.

2.7 LET US SUM UP

After reading this unit you learned that:

� The chemical reactions in the body produce waste materials, whichhave to be removed out, through excretion.

� Minerals are transported from one part of body to another in both plantsand animals.

� Performed the experiment of 'Ascent of Sap' to demonstrate transportof water and food elements in plants.

� The structure, function and uses of simple and compound microscopes.� Prepared temporary slides of onion peel and observed permanent slides.� Understood characteristics of process of External and Internal (tissue)

respiration� Differentiated Aerobic and Anaerobic Respiration.� Tested the presence of some common food adulterants.

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Answer 11. The process of transpiration creates a pulling force throughout the

plant body, and ensures constant movement of water & minerals fromthe roots to all parts of plant.

2. Evaporation is the loss of water in the form of vapour from thesurface of the water body. Transpiration is the loss of water in theform of vapour from the leaf surface through the openings on theleaf surface called stomata.

2.9 GLOSSARY

Microscope Instrument used to observe things living/deadorganism, cells and tissues which cannot be seen bythe naked eye or even through a hand lens.

Respiration The process of taking in oxygen and releasing carbon-di-oxide and energy from food.

Breathing Process in which oxygen is taken inside the body(External (inspiration and carbon-di-oxide is releasedRespiration) (expiration).

Aerobic The process in which oxygen is used to oxidise foodRespiration in the cells releasing carbon-di-oxide, water and energy

Anaerobic The process in which food is broken down chemicallyRespiration without oxygen, releasing carbon-di-oxide, ethyl

alcohol and energy.

Adulteration The mixing of undesirable substances in the foodof food material e.g. lead chromate mixed in turmeric power

acts an adulterant.

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Skill of PerformingScientific Experiments UNIT 3 PURIFICATION OF WATER,

ARTIFICIAL GREENHOUSE,MODEL OF RAIN WATERHARVESTING

Structure

3.1 Introduction3.2 Objectives3.3 Purification of Water3.4 Making Artificial Greenhouse3.5 Rain Water Harvesting3.6 Compost Pit3.7 Let us Sum Up3.8 Answers to Check Your Progress3.9 References

3.1 INTRODUCTION

You will agree that the best way of learning science is by doing science. Inthis unit you will learn some strategies of teaching experiments in science.Some of these experiments are based on concepts which you have read inthe earlier units. Experiments have been discussed in a manner whichactively involve students, foster their creativity and enable them to relatethe processes with their real life situations.

3.2 OBJECTIVES

After going through this unit, you will be able to� list different methods of conversion of non drinkable water to drinkable

water.� perform experiments related to methods of purifying water, artificial

greenhouse, rain water harvesting and composting etc.� relate artificial Greenhouse system to environment.� explain methods of making model of rain water harvesting.� classify natural means of rain water harvesting to artificial ones.� explain method of making compost pits.

3.3 PURIFICATION OF WATER

Due to non eco-friendly human behaviour water is getting contaminated.We pollute it by washing our clothes, bathing our cattle and throwingwastage materials in water resources. Due to contamination numbers ofharmful bacteria are generated in water. Disease free drinkable water isessential for our existence. Purification of water is, therefore, very importantstep in this regard.

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Purification of WaterArtificial Greenhouse,

Model of Rain WaterHarvesting

Methods to purify water1. Non drinkable water can be converted into drinkable water by filtration

process. Three pots experiment is based on this process.2. When non drinkable water is boiled germs die and dirt is precipitated

and thus water can be made potable.3. By using some reagents like Potassium Permanganate (KMNO

4) water

can be purified. In villages pond water is purified by using this chemicalcalled lal dava. Chlorination is also important in this regard.

Activity 1You will perform this activity by involving students. Take3 pots as seen in figure. Make small pores in base of thesepots; cover these pots with cotton fibre. Put concretematerial in first pot and sand in second & charcoal inthird pot. Now pour non drinkable water at first pot.What do you see in the lowest container?Water gets collected in the lowest container.It is pure water. It is due to filtration.

A variety of filters are used in Indian houses. Some aresimple filters while some have facility of Ultraviolet rays.These rays kill the germs in water and make water potable.

Activity 2Collect photographs of modern water purifiers so thatstudents can have a better understanding of differentcomponents in them.

Activity 3 Group discussion may be organized in following points:

o How suspended particles and germs can be removed from water?o Why KMNO4 is used in ponds?o Why chlorination of water is important?o How non drinkable water is converted into drinkable water?

Water supply department of the Municipality undertakes water purificationwork on a large scale. They have big water purifier plants located in differentparts of the city. A field visit to these plants would be of great help. One cansee that these plants use bleaching powder in large amounts for killing germspresent in water.

Fig 4.1: The ThreePots Experiment

CHECK YOUR PROGRESS-1Note: a) Write your answers in the space given below

b) Compare your answers with those given at the end of the unit.

1. Write some methods of purifying water______________________________________________________________________________________________________________________________________________________

2. What is filtration process?______________________________________________________________________________________________________________________________________________________

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3.4 MAKING ARTIFICIAL GREENHOUSE

Greenhouse is a shelter for green plants, plant nursery, etc. Walls ofGreenhouses are directly in contact of outer atmosphere. They absorb heatand keep the inside part warm. It is covered by a sheet.

By visiting actual Greenhouse we can know about them. In the areas whereGreenhouses are not available to visit we can show photographs of actualGreenhouses to students. With the help of stick of bans or wood, we canmake cage of a Greenhouse. Walls can be made of plastic sheets.

Activity 4Instruct the students to take two transparent jars and open lids of both jars.Next tell them to put the thermometer inside these jars and place these jarsin shady area. Let them note the temperature. After some time, tell them tokeep both jars in the sunlight. Close the lid of one jar. Remove lid of otherjar. Note the temperature. Keep these jars in sunlight for about two hours.Note temperature of both jars. Now place these jars in shady area. Notetemperature again. Ask the students to record their observations ontemperature difference in both the jars.The jar having lid shows slower fall in temperature while open jar showsrapid fall in temperature due to exchange of gases.



1. What is Greenhouse effect?______________________________________________________________________________________________________________________________________________________

2. How does earth behave as a Greenhouse?______________________________________________________________________________________________________________________________________________________

3. Why is the making of artificial greenhouse essential?______________________________________________________________________________________________________________________________________________________

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3.5 RAIN WATER HARVESTING

Water is very important for life. Due to deforestation water level is graduallydecreasing in earth. Therefore, it isnecessary to conserve water byapplying various methods. Rainwaterharvesting is one of these. It can beused for a variety of purposes.

As seen in Fig. 4-2 water from roofof house is collected in small watertank, other method is rain waterharvesting by making ploy tank. Inhilly area rain water can also bestored by this method. By using low

cost material we can make low density polythene for this tank.

For water harvesting in house and underground tank following material isrequired(i) Funnel(ii) pipe(iii) wood for making model for house(iv) iron net for underground water tank.For making poly tank we can make low density polythene by using lowcost plastic material

In hilly area water is harvested as seen in figure. At base of sloppy hills wemake raw pond. Water from sloppy hill is stored in these ponds. This wateris absorbed by soil and this is important in maintaining water level of earth.

Such types of naturally madeponds are known as khal in locallanguage.

By knowing rain waterharvesting we can understandvalue of water. Water conserveddue to rain water harvesting canalso be used for other purposessuch as irrigation.

1. Rain water harvesting can be explained through power point presentationof flowing rain water and it's storage with help of rainwater harvesting.

2. With help of chart and poster rain water harvesting can be illustrated.3. Lecture cum demonstration – model of rain water harvesting can be

demonstrated with lecture.4. In rainy season with help of model of rain water harvesting the harvesting

can be practiced in own house.

Fig 4.2: Rainwater harvesting usinglow cost method

Fig 4.3 Rainwater harvesting in a hilly area

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5. In hilly regions there are natural means of rain water harvesting. Naturalponds are made at the valley of slopy hills. These are locally calledkhals. These should be visited.

6. Water harvesting of rain can be illustrated through story telling andplaying drama.

7. A video film we can make on rain water harvesting. By showing it onecan understand rain water harvesting.

Activity 5Form a raw at the valley of slopy hills. After rain observe how much wateris stored here.



1. Why is water conservation essential?______________________________________________________________________________________________________________________________________________________

2. How is rain water harvested naturally?______________________________________________________________________________________________________________________________________________________

3. What is the significance of rain water harvesting in hilly areas?______________________________________________________________________________________________________________________________________________________

4. Mention two methods demonstrating rain water harvesting.______________________________________________________________________________________________________________________________________________________

5. What is low density polythene______________________________________________________________________________________________________________________________________________________

6. What role does rain water harvesting play in maintaining levelof water?______________________________________________________________________________________________________________________________________________________

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3.6 COMPOST PIT

Due to regular use of artificial manure soil may become infertile. Formaintaining fertility of soil making of compost pit is necessary.

Activity 6Take students outside to the school lawn or nearby park.Ask students to digsoil to a suitable length, breadth and half meter depth. Put cattle's dungand urine, heap of leaves of this cavity. After making one layer put someamount of soil and ash. Make another layer by applying same method tillgetting height of 1.5 meter compost pit is ready. Go on adding canteenwaste and other organic waste in the pit and observe the changes. Wetnesshas to be maintained properly as abundance as well as scarcity of watermight bring down the rate of decomposition.

Activity 7You could organize a visit to a compost pit in the village or organisediscussion with a farmer as an expert of making compost pit.Power point presentation may also be used to explain the functioning ofcompost pit.



1. What is compost?______________________________________________________________________________________________________________________________________________________

2. How is a compost pit made?______________________________________________________________________________________________________________________________________________________

3. Why are soil, ash, and animal's urine mixed in compost heap?______________________________________________________________________________________________________________________________________________________

3.7 LET US SUM UP

In this unit, you learned� Scientific process involves a series of logical steps, like selection of

problem, observation, hypothesis, experimentation and analysis ofresults to prove the hypothesis.

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� About process involved in purification of water, preparation ofartificial Greenhouse, compost pit and model of rain water harvesting.


Answer 11. Filtration, boiling of water and use of some reagent like KMNO4.2. In filtration process water is passed from one layer to another. Three

pots experiment is based on filtration process.

Answer 21. Greenhouse is made up of iron cage for growing nursery, plants etc.

Inside atmosphere remains warm. Some gases like CO2, carbonmonoxide, methane etc. absorbs heat and help in heating of earth. Thesegases are called as Greenhouse gases and their effect is Greenhouseeffect.

2. Greenhouse gases behave as walls of Greenhouse in earth. These gasesabsorb heat and check its radiation to atmosphere.

3. With help of artificial Greenhouse we can understand concept ofGreenhouse.

Answer 31. Water is widely used compound by living organism.2. In hilly areas at the base of sloppy hills the natural ponds are made.

Water from slope of hills is collected here and thus naturally harvested.3. Rain water harvesting in hilly areas is very significant because here in

four months of rainy season there is heavy rain. Water from rain canbe harvested and can use for next months.

4. By visit of resources of natural rain water harvesting and by showinga video film.

5. Low density polythene can be made by using locally available plasticmaterial it is used in making poly tank.

6. Due to stored water by rain water harvesting some of water is absorbedby earth and level of underground water is increased.

Answer 41. When dung and urine of cattle, heap of leaves, and remains of crops

are decomposed by decomposers such as bacterial, this decomposedmaterial is called as compost.

2. We can make compost pit by digging soil in suitable length, breadthand half meter depth. We put dung, heap of leaves, urine of cattle, etc.to this pit in different layers. After forming a layer we put some soiland as on it. Abundance of water and deficiency of water both maydecrease level of decomposition thus we should cover the pit withgrass etc.

3. Soil bacteria from soil also reach to compost. They help indecomposition. In the process of decomposition some acids are formed.Due to these acids decomposition is negatively influenced. When ash

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is mixed it neutralize these acids. Due to animal urine amount of nitrogenis received by compost.

3.9 REFERENCES

Gyan Vigyan book for Class IV published by SCERT Uttrakahand NarendraNagar Tehri Garhwal (2005).

Vigyan aur Hum for Class 7 and 8 (2005-06) Vidhyalayi Shiksha UttarakhandDehradun.

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Skill of PerformingScientific Experiments UNIT 4 SCIENCE CORNER

Structure

4.1 Introduction4.2 Objectives4.3 Concept of Science Corner

4.3.1 How to develop a Science Corner in School4.3.2 Activities in a Science Corner

4.4 Real Specimens4.5 Collection and Preservation of Specimens4.6 Posters4.7 Charts4.8 Album4.9 Experimental Cards4.10 Reference Books and Magazines4.11 Apparatus and Equipments4.12 Low Cost Teaching Aids4.13 Science Kit4.14 First Aid Box4.15 Let Us Sum Up4.16 Answers to Check Your Progress

4.1 INTRODUCTION

The word science is derived from a Latin word scientia, which meansknowledge. It is also referred to as a way of acquiring knowledge based onscientific method (http://en.wikipedia.org/). It is important for theclassrooms to be equipped with simple scientific apparatus and equipmentsto enable students to learn science by doing, in the presence of the teacher.Since all schools do not have science laboratories, especially in the ruralareas of the country, you can build a science corner in the classroom usinglow cost materials, charts, specimens of plants and animals, models etc. Inthis unit you will learn some ways of creating a science corner in theclassroom and the methods of using that corner by involving students inperforming simple scientific experiments and activities.

4.2 OBJECTIVES

After reading this unit, you will be able to� explain the meaning of Science Corner and how we can make a science

corner.� develop a science corner in the school� describe the benefit of science corner for classroom transaction.� identify plant and animal specimens.� describe the process of collection and preservation of various

specimens and the precautions needed.� prepare posters, charts and albums as teaching aids.� use experimental cards for performing experiments

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Science Corner� discuss the need and importance of reference books and magazines ina science corner

� prepare low cost teaching aids.� identify simple apparatus and equipment required for a science corner� develop a science kit.

4.3 CONCEPT OF SCIENCE CORNER

Rohan, a student of class VI comes with a thermometer and tells his friendsthat it can measure temperature. His friends have not seen it earlier, hencethey are unable to recognize. One boy Rahul said it was a thermometer.Rohan describes that last Sunday he was ill so his mother used this to seehow much fever I had. Rahul took them to his mother to know more aboutit. Mother informs the students that it was clinical thermometer whichmeasures body temperature. It has a bulb at the bottom filled with mercury.It works on the principle that liquid expands when heated. Mother tells thechildren that there are so many things in our house and surrounding areaswhich we do not know how to use them in science experiments. As she isa teacher herself she says that we can make a science corner in our schools.

The main motive to have a science corner in our schools is to attain practicalknowledge. The topics of science can be easily explained through simpleexperiments to clarify doubts among the students. It can also improve thequality of education. The teacher can motivate the students to performsimple experiments in his/her presence.

We can keep scientific instruments related to the current topics in theirscience text books. These may include simple mirror, lenses, thermometers,flasks, beakers, petridish, test tubes, prism, glass rods and tubes, burners,spirit lamps, Real specimen of various plants and animals. Process ofcollection and preservation of specimen is also very important. Let us seethat this unit helps you all in acquiring knowledge about specimens, sciencecorner, collection and preservations of specimens.

In our country, there are many schools where science laboratory are notavailable. So the students do not get the practical exposure to the scientificprinciples. By utilizing low-cost materials, charts, working models, wecan create a laboratory in the classroom itself. The main motive of thescience corner is to improve the quality of education among the studentsby the motivation of teachers (Science can be learnt best by doing).

4.3.1 How to Develop a Science Corner in School

We can develop the science corner in our school by doing activities of suchtypes and collecting the material related with science. Real specimen ofplant, root, stem, leaves, flowers, fruits and seed can be shown to the studentsby the teacher in the classroom. Real specimen like insects, organs likeheart, lungs, snakes, reptiles, frog, and birds can be shown to the student.Regarding physics experiments mirrors, lenses, glass slabs, prisms,

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thermometers, magnets and for chemistry teaching we can use beakers,funnels, conical flasks spirit lamps etc.

Charts: A flowering plant, Part of plant cell, Animal cell, Variousmodifications of root, stem, etc.

Models: Like heart, lungs, circulatory system, digestive system, nervoussystem, skeletal system, etc.

Electrical Gadgets: Battery, dry cells, volta cell, electric bulbs toconnecting wires, electric bell etc.

Reference Books for various experimental guidance.

Field Visits to Planetarium, Botanical and Zoological Garden, ScienceMuseum and Industrial plants.

4.3.2 Activities in a Science Corner

The drawing and picture of a rainbow can be displayed in the sciencecorner

Activity 1 (Formation of Artificial Rainbow)Put some water in the beaker and place a strip of mirror as shown in thefigure. You will observe that the rainbow must be formed in the oppositedirection when the dispersion of light will take place though the light. (Partof mirror strip dipped in water)

This simple activity shows spitting of white light into seven colors by wayof formation of artificial rainbow.

Experiment to show water and air are necessary for seed germination.Take three beakers say A, B, C respectively. Put one seed in each beaker.Pour water in beaker A till the seed dipped fully in it. In beaker B, put thewater to the extent that the seed may be partially exposed to air and partiallyto water. Let the seed in beaker C is exposed to air only. Now observe thegermination of seeds in the three beakers for few days. The germination of

Fig 4.1: Experiment showing splitting of white light to form a rainbow

ROYGBIV

MIRROR STRIP

WATER

BEAKER

ARTIFICIAL RAINBOW

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Science Cornerseed in beaker B occurs since it is exposed both to air and water. The seedin beaker A is only submerged in water only and it is not in contact with theair in atmosphere hence no germination while in seed in beaker C does notshow germination since it is in contact with air only but not water.

Take any empty plastic bottle of cold drink or beverage. Fill the half thebottle with Sodium Carbonate (Na

2CO

3) solution and insert a glass test

tube in it as shown in the figure.

Fig 4.2: Seeds left to germi-nate in a bowl

Fig 4.3 Diagram ofgermination of seeds

Fire Extinguishers

Fig 5.2: Laboratory set up of a Fire Extinguisher

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The bottom of the bottled should be dip in the sodium carbonate solution.Now fit a cork at the mouth of test tube before adding sulphuric acid in thetest tube and affix a thin iron rod in the cork which should have the one andhalf time more length than the length of the test tube. Make a hole near thetop of the bottle and when you will press the iron rod the test tube willbreak and sulphuric acid will react with sodium carbonate solution andcarbon-di-oxide gas will be produced. We will observe that when the gas ispassed over the burning candle, it will stop burning. This shows that thegas produced in the fire extinguisher is carbon dioxide.

4. Newton's Disc

Activity 2Take A Disc (saucer, compact disc, cardboard plate,etc.) of any material. Colour it with seven coloursviz VIBGYOR (Violet, Indigo, Blue, Green, Yellow,Orange, Red). Now affix a rod in the centre of thedisk and rotate it. You will observe that the rotatingcolourful disc appears white. This shows that thelight is the combination of seven colours.

5. Separation of Components from a Mixture

Activity 3Ask the students to separate the mixture of grains and stone? Tell them tonote down some other ways of separating this mixture, other thanhandpicking. They might suggest various ways like winnowing, gravityseparation etc.

Discuss the advantages and disadvantages of each method and help studentsarrive at a conclusion to decide the best method.

Fig 5.3: Newton's Disc



1. Name the instrument used for measuring body temperature.__________________________________________________

2. Name the metal used in liquid thermometer.__________________________________________________

3. Name the seven colours of light______________________________________________________________________________________________________________________________________________________

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Science Corner

4.4 REAL SPECIMENS

In the section the students can be made aware, what real specimens are. Inthe day to day life, every body comes across some specimens of a particular

4. Which gas is used in fire extinguisher?__________________________________________________

5. Name different methods used for separation of solids from solids.____________________________________________________________________________________________________

6. Name the necessary conditions for the germination of seed.______________________________________________________________________________________________________________________________________________________

Picture of a plant specimenPictures of some real animal specimens

item. The primary and elementary school children can be taught that if wehave samples of an item in reality, these can be termed as real specimens.

Science is termed as a study based on observations and collection of factsfor the preparation of a hypothesis. This hypothesis whenever verifiedpractically leads to evolution of facts. The real specimens are the collectionsmade from the real life taking in mind. These specimens can be divided intwo categories.

i. Perishable real specimens.ii. Preserved real specimens.

Activity 4Ask all the students of a group to collect a realspecimen each showing as many parts of a plantas possible.

o Some students may bring a sample with root,stem, leaves etc. but missing flowers, fruitsand seeds.

o Some students may be able to bring aspecimens have all the parts viz. - roots, stem,

Fig 5.4: Diagram of a flower-ing plant showing its parts

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leaves flowers, fruit or seed.

You can conclude about the parts.

Activity 5Repeat the above activity with thetypes of carbon

o The students can be madeaware that

o Carbon is blacko Carbon is present in all living

being.o It is an elemento They can be told about the

allotropy of carbon.o Inform students that diamond is also an allotrope of carbon.o From different samples of carbon collected by children, it can be

brought to their notice that all the allotropes produce CO2 after burning

in air.

Difference between real and artificial specimens

Real specimen are those which can be observed in real life e.g. living animalsand plants and are real working models in real sense.

Artificial specimens are those that are similar to real species but artificiallyprepared either static or robotic.

Allotropes of carbon



1. What are the real specimens?____________________________________________________________________________________________________

2. What is the importance of real specimen?____________________________________________________________________________________________________

3. Tick mark the correct answers(a) Real specimen can be collected from the real life.(b) No conclusion can be drawn from the study of real specimens.(c) Research work follows from the critical study of real specimen.(d) Real specimens can be preserved for future use.

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Science Corner4.5 COLLECTION AND PRESERVATION OF SPECIMENS

Collection and preservation of specimen is very important. By collectingand preserving different specimen, students know their characteristics, theirhabits, habitat and their economic importance.

Have you seen stuffed animals and birds in the museum? They are displayedto see animals in reality. The real size, shape, texture and look can be seenwhen they see the preserved ones.

Preserved Plant and Animal Specimens

Activity 6Instruct the students to collect samples as below

� The whole plant/animal wherever is possible.� The specific part of the specimen.� Sorting out unwanted portion of the specimen� Retaking the required specimen as per need.

The specimen collected as above can have more than required percentageof moisture which can hamper their storage. This moisture content can bereduced by proper dehydration process through alcohol. The dried upspecimen can be preserved into the 5- 40 percent solution of formaldehyde,according to the nature of the specimen.

� There can be mishandling while collecting the specimen.� Precautionary measures have to be maintained.� Proper preservatives must be used.� There may be some snags the whole process.

Examples of various collections can be as follows: Pigeon, Wall lizard,earthworm, scorpion, frog, flies, fishes, Skelton of different animals, leavesof various plants, radish, carrot, cauliflower, bryophyllum , fern, palm.

You talk to expert and invite experts from other educational institutions.He/she can guide the student to collect more and more information aboutscience from newspapers, magazines and media any other information canbe presented on bulletin board.

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Activity 7Ask students to prepare scrap books on different ideas. Guide them to collectinformation on plants, animal, diseases, environment and new discoveries,herbarium (leaves, flowers, roots, seeds, wings, etc.). They can even collectfeathers of various birds.

4.6 POSTERS

Posters are diagrammatic representation or brief account of a theme,thematic representation or cartoonic representation of a theme or concept.Posters may be in the form of symbols, slogans, pictures, and flow charts,cartoon or bullet points. Posters explain the theme briefly. Here are sampleof posters.



1. Write the stages in preserving a plant and a reptile in a bottle?______________________________________________________________________________________________________________________________________________________

2. What are the uses of preservation?______________________________________________________________________________________________________________________________________________________

3. Visit a museum and observe the preservation process and preserved specimens.__________________________________________________

4 Name the plants which can be collected easily from our surrounding.__________________________________________________

5 Name the animals which can be preserved.__________________________________________________

WATER POLLUTION

Causes of Water Pollution� Adding industrial effluents, chemical effluents into water bodies� Washing clothes, cattles in the river, lake etc.� Frequent clearing of water bodies

Dangers of Water pollution� Diseases caused: Diarrhea, vomiting, other diseases etc.� Water is potable� Water bodies filled with aquatic plants� Cause algal bloom� Dangerous to fishes

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Science CornerYou can prepare posters and keep them in the science corner. You can alsoconduct poster competition to students by giving certain themes like waterwaste/solid waste management, natural calamities, etc. and select certainposters and keep in the science corner. Here is the simple Slogan Posterdiscouraging use of the cell phones while driving.

AVOID CELL PHONEDon't use the cell phone while driving; it may be a call from hell

While teaching about pollution, waste management chapters you can usethe posters and teach. You can also make the students to make posters forcertain concepts like sound pollution, biodegradation.

CHECK YOUR PROGRESS 4Note: Write your answers in the space given below

1. What did you learn from the posters you have seen in thesci ence lab?____________________________________________________________________________________________________

2. Make a cartoon on tsunami.

4.7 CHARTS

Chart is a good teachinglearning aid for science, especially when youteach certain microscopic organism like amoeba, paramecium etc. andcertain cross-section of stem, leaf, etc. This also enables the students tounderstand faster and to draw the diagram.

The chart can be hung on the walls of theclassroom and using a stick, teacher can pointout the diagram and show the parts and teach.You must remember the following:

� The diagram drawn in a chart must becolourful, big and legible.

� The parts of the diagram should be labeled.� Diagram should be drawn proportionately,

according to the size of various parts.

CHART

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� Some projected parts of the diagram can be drawn in a chart and theoutline can be cut and can be made projected.

� Certain apparatus, equipments can also be drawn on the chart.� Certain flow charts can be drawn on a chart

CHECK YOUR PROGRESS 5Note: Perform the given exercise

You can prepare charts for graphical representation like compositionof air, life span of different animals, etc. You can also ask the studentsto make charts on different topics.

4.8 ALBUM

Albums are booklets of collection of materials classified under one heador theme. It can have Pictures of plants (hydrophyte, mesophyte andxerophytes), animals (vertebrates and non-vertebrates, insects), and picturesof birds. These pictures can be pasted on the album.

Activity 8Any interesting news item from newspaper on astronomy, regardingsatellites, stars, lunar and solar eclipse, tsunami etc. can be cut along withphotos and stored in the scrap book. Instruct students to prepare an albumin a given theme and keep in the science corner.Ask students to prepare scrap books on certain assigned topics like pollution,waste management, earthquake, forest fire, etc. You can utilize the picturesin the album when teaching the particular topic.

Whenever you come across any novel pictures, news or information in thenewspaper or magazines, you too can cut and collect the items and store inthe box and then utilize for album preparation.

How will you use the science corner especially with the albums when youteach plants and animals?

Projects

A variety of projects can be planned taking into account the resourcesavailable and the interest of the students. You can ask students to collectthe specimen of different plants and prepare their herbaria. You can alsoinstruct them to collect different insects and prepare a display. Types ofcrops in the locality could be an issue for a group of students while diseasesin the locality could be an issue for another group of students.

4.9 EXPERIMENTAL CARDS

You can simple experiments or ask students to do them in groups or inpairs. The various sequential steps of the experiments are given in the cards;following the steps, you and the students can do the experiments.

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Science CornerObjectivesThe learner is able to� do the experiment on their own.� Do in groups or in pairs� Procure the materials needed for the experiments from the tale.

Teaching Strategies� Pick up the experimental cards� Procure the materials needed� Perform the experiments� Note your observation

Examples of the experiments using cards

SOLUBILITY TESTSalt, sugar, sand - which are soluble or which are not soluble.Beaker, salt, sugar, sand, water� Take beaker� Put salt� Add water� Stir well� Observe whether soluble or not� Repeat with sugar and sand� Observe whether soluble or not� Note down which is soluble and which is not souble.

CONDUCTION OF HEATPencil lead (graphite), Metal rod, glass rod, wooden stick, burner� Heat one end of pencil lead.� Touch the other end after some time.� Can you feel the heat?� If so, then the pencil lead is good conductor.� Repeat with wooden rod� Observe and note your observations

Note to the TeacherTeacher can make experimental cards for various concepts and ask thestudents to perform the experiments. The following points have to be keptin mind when the teachers are preparing the experimental cards

� The cards must have simple steps to perform the experiments.� The diagram of the devise used for the particular experiment should

necessarily be given in the card.� All the materials headed for the experiment have to be kept near the

experimental cards.

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� If any precautions, that has to be mentionedin the card.

� The sentences/words used in the cardshould be simple and can be understandableto the learners.

� The card should have 5 cm x 7 cmmeasurement and that may be laminatedand colourful and attractive.

Example of sentences/ questions to be written on the cards-

What happens when you add water to sugar and sand?Give reasons for what you observed?

4.10 REFERENCE BOOKS AND MAGAZINES

Reference books and magazines play an important role in science teachingand learning. It will build the enthusiasm of students and improve readingskills too.

Teaching PointsWhen you teach about bryophytes/ferns you tell them about the plantswhich are present near the walls of well which are marshy are calledbryophytes. The plants used for decorating purpose at home which willnot give flowers are called ferns. Ask them to observe the brown spots onthe margin of the older leaves. They are nothing but spores.

Experimental Cards on Protozoa

CHECK YOUR PROGRESS 6Note: Ask the students to answer

1. Which books did you refer today?__________________________________________________

2. What are the interesting points you read today?__________________________________________________

3. Did you have any doubts or confusion for clarification?__________________________________________________

Ask the students to refer the books on Bryophytes and Pteriodophyte atlibrary and learn more interesting points on ferns. Likewise, when youteach about pollution or global warming you can ask the students to referlibrary books on pollution and global warming and get interestingobservation.

You may conduct small seminar on a given topic for which you may askthe students to refer to books.

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Science CornerTips for youPrinted materials in the science corner must be very interesting andillustrative. You can prepare the printed materials if there is no materialavailable for any concept. For example, when you want to prepare a materialon Bryophytes, you can write how it originated, first as land form, how thestructure is having leaf-like, stem-like, root-like organs and the sporophyteand where it is available (on the marshy walls of the well) and how onecan see the plant through the magnifying lens. It can also be collected andteased with the needle and can be seen under dissection microscope.

Here you can also explain how to use the dissection microscope.

Activity 9� Put the plant on the microscope slide.� Put little glycerine.� Slide the cover slip on the glycerin gently without any air bubble.� Keep the slide on the field and adjust the eye piece and the mirror to

provide enough light on the specimen and look through the eye piece.� Ask the students to draw the diagram.

� First explain the concepts.� Give enough references.� See whether the books are available in the library or internet.� See whether the language is simple.� If not, prepare small booklet of your own and keep in the library or

learning corner (Science Corner).� Ask the students to read and get notes out of it.� Ask the learners to have a discussion with the other students.

There are also magazines like Science, Nature, Resonance, etc which canbe made available in the library.

4.11 APPARATUS AND EQUIPMENTS

Science laboratory is provided with so many apparatus and equipments.For example, delivery tube, wire gauze, test tube, conical flask, test tubestand, etc.

ApparatusYou can keep the following in the science corner.

(i) Labwares: Beaker, conical flask, single hole rubber cork, two holedrubber cork, delivery tube, gas jar, test tube, test tube holder, wiregauze, tripod, spirit lamp, Bunsen Burner, Stirrer, microscopic slides,cover slips.

(ii) Hardwares� Multimedia� Galvanometer� Ammeter

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� Simple circuit� Ganongs' photometer� Respiroscope� Apparatus for O

2, CO

2, H

2 preparation

(iii) Microscope� Dissection Microscope� Compound microscope

(iv) Optical Bench� Mirror� Stand� Lens� Slab� Prism� screen

(v) Chemicals� HCl� H

2SO

4

� Sodium Carbonate� Sodium Chloride� Litmus paper� pH paper� Glycerine� Pins� Slides� Cover slips

You can show the apparatus like Beaker, Test tube, Funnel, Pipette andBurette to the students and can explain about the apparatus and their uses.

Teaching strategy

� Experimentation� Demonstration� Observation

You will demonstrate these exemplar activities to the students

Activity 10

Preparation of dil. HCL acidTake the Beaker. Add water. Pour concentrated Hydrochloric acid drop bydrop. Test it with litmus paper

Activity 11Preparation of Hydrogen gas

Take a test tube. Put Zinc metal in it. Add dilute Hydrochloric acid drop bydrop. Observe the bubbles coming out. Collect the gas in another test tube.Test the gas by a burning flame which produces a 'pop' sound. It's ahydrogen gas.

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Science CornerActivity 12Ganong's Potometer

� Show the apparatus� Ask the students to observe the parts.� Perform the experiment� Make the observation



1. What are all the apparatus you have seen in the class laboratory?__________________________________________________

2. Can you name them and draw their diagrams?__________________________________________________

3. Can you give the use of these apparatus and equipments that youhave seen in the laboratory?______________________________________________________________________________________________________________________________________________________

4.12 LOW COST TEACHING AIDS

Low cost teaching aids means teaching-learning materials (TLM) preparedout of waste materials. You can prepare same TLM and can keep in theScience Corner.

Following are the exemplar activities to make working and static models.

Activity 13Water Pressure ExperimentTake a water bottle. Make 3 holes on the lateral sides in different heights.Pour water by closing the holes. Water will come out with different pressures.Hence it is inferred that water has different pressures at different heights.When height increases, pressure also increases.

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Activity 14Thermocole ModelsYou can draw, Plant Cell, Animal Cell on the thermocole using differentcolours.

4.13 SCIENCE KIT

Primary and upper primary schools normally will not have separate sciencelaboratories. Hence science kit is supplied to those schools. Knowing thekit and using it effectively is very important.

When you teach about different properties of mater, you can use thematerials available in the kit like solids, liquids and gases and explain theproperties.

Activity 15You can involve the students to perform the following experiment usingmaterials kept in the science kit compiled in the classroom.

� Ask students to take solids like pebbles, stones, beaker, balloon fromthe kit

� Instruct them to arrange the pebbles in a container. What does thisshow?It shows that pebbles occupy space.

� Tell the learners that solid occupies space.� Ask them to pour water in a beaker.� Ask them to observe how water, which is a liquid, occupies space.� Instruct them to blow the balloon.

What happens?The balloon blows up.What does this prove?This proves that gas also occupies space.

Likewise, the materials like rubber band, glass tube, metal wire, stonescan be used to perform experiments to show elasticity, stirring of solution,heat experiment etc.

Note� You must prepare a list of materials in the science kit.� You can plan the possible activities using the materials in the

science kit

� Science kit can be prepared by the teachers by listing out simplematerials like stones, sand, sticks, papers, bottles, pins, rubber band,plastic materials, salt, sugar etc. and kept in the science kit. Small testtubes, beaker, some salts, water, acids, litmus paper can also be kept inscience kit.

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Science Corner� When you ask students to use the kit, give enough instruction to usethe materials.

� Students collections like leaf, flowers, herbarium, insects can also bekept in the kit.

CHECK YOUR PROGRESS 8Note: Perform the given exercise

Ask the students to use the material and perform the experiment givenon chit.

4.14 FIRST AID BOX

The children are prone to get injuries at school either in the classroom orplayground. Hence every class must have a First Aid Box.

Materials in the first Aid Box� Cotton� Spirit� Ointments,� Gauze cloth� Antibiotic cream� Plasters� Hydrogen peroxide� Bandage cloth

You can teach the students to make use of the First Aid Box whenever theyare in need. You can teach them when the students get wounded, they canwipe the wound with spirit and put a disinfectant on it.

4.15 LET US SUM UP

In this unit you learned that:

� Science Corner is important and crucial for improving the quality ofScience teaching in the classrooms.

� Components of a Science corner and the activities that can be performedduring classroom transactions.

� Preparation of Science Kits, Low Cost Teaching Aids like posters,charts, albums, stethoscopes etc.

� Methods of collection and preservation of specimens� Use of experimental cards for performing simple experiments.


Answer 11. Thermometer2. Mercury

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3. Violet, Indigo, Blue, Green Yellow, Orange, Red4. Carbon-di-oxide5. Winnowing, hand picking, gravity separation6. Air, Water and Sunlight

Answer 21. Those which can be observed in their actual form (shape and

size) e.g. plants, animals2. The actual structure of the real organism can be studied and

conclusions can be drawn by the teacher and students.3. (a), (c), (d).

Answer 31. Collection, drying (dehydration), preserving in 5% - 40%

solution of formaldehyde.2. It is possible to study the habits, habitats and other

characteristics of the specimens.4. Rose, tulsi, ornamental plants5. Fish, lizards, frog, pigeons, cockroach etc.

teaching of science

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