science and technology std 9th

7/23/2019 Science and Technology Std 9th

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No part of this book may be reproduced or transmitted in any form or by any means, C.D. ROM/Audio Video Cassettes or electronic, mechanical

including photocopying; recording or by any information storage and retrieval system without permission in writing from the Publisher.

STD. IXScience

andTechnology

Written as per the revised syllabus prescribed by the Maharashtra State Board

of Secondary and Higher Secondary Education, Pune.

TEID : 881

Printed at: Repro India Ltd., Mumbai

Fifth Edition: April 2015

Salient Features

• Written as per the new textbook.

• Exhaustive coverage of entire syllabus in question answer format.

• Covers answers to all textual questions, intext questions and activities.

• Includes Questions based on diagrams / flow-charts.

• Includes Higher Order Thinking Skills (HOTS).

• Ample Solved and Practice Problems.

• Neat and labelled diagrams.

• Attractive layout of the content.



Preface

In the case of good books, the point is not how many of them you can get through, but rather how many can

get through to you.

Science is the observation, identification, experimental investigation and theoretical explanation of

phenomenon. It is the study of physical, chemical and biological aspects of natural phenomenon. It dealswith inherent properties of space, matter, energy and their interactions.

Technology is the application of scientific knowledge for the benefit of mankind. It includes the use of

materials, tools, techniques and knowledge to make life more pleasant and work more productive. Whereasscience is concerned with how things happen, technology focuses on making things happen.

The study of Science and technology requires a deep and intrinsic understanding of concepts. Hence to ease

this task we bring to you “Std. IX: Science and Technology” a complete and thorough guide extensivelydrafted to boost the students confidence. The topicwise question and answer format of this book helps the

student to understand each and every concept thoroughly. It includes all the important definitions, laws and

formulae. Neat and labelled diagrams are provided wherever necessary. Numerical problems at the end ofrelated topics help the students to understand the technique of solving numerous problems efficiently.

Lastly, I would like to thank all those who have helped me in preparing this book. There is always room forimprovement and hence we welcome all suggestions and regret any errors that may have occurred in the

making of this book.

A book affects eternity; one can never tell where its influence stops.

Best of luck to all the aspirants!

From

Publisher

No. Chapter Name Page No.

1 World of Matter 1

2 Understanding Matter 14

3 Inside the Atom 26

4 Counting Matter 38

5 Cell: The unit of Life 50

6 Life: Simple and Complex 70

7 Life Around You 94

8 Highway to Health 117

9 Quality Food, Quality Life 142

10 Moving Objects 166

11 The Laws of Motion 183

12 The Pull of the Earth 198

13 Why Bodies Float 212

14 Energy : The Driving Force 225

15 The Music of Sound 243

16 Bonding with Ecosystems 260

17Solid Waste – Ecofriendly

Management273

ont nts

Note: Textual Questions are represented by * mark.

Intext Questions are represented by # mark.

Section A : Chapter No. 3, 4, 10, 11, 12, 13, 14, 15, 16

Section B : Chapter No. 1, 2, 5, 6, 7, 8, 9, 17



Std. IX: Science and Technology

2

Publications Pvt. Ltd.Target

Answer the following questions

in one sentence each

17. ______ is a sublimatory substance.

(A) Iodine

(B) Sodium chloride

(C) Potassium permanganate

(D) Calcium oxide

1.6 Absorption of heat

18. The outer side of the container of a solar

cooker is painted ______.

(A) blue (B) black

(C) white (D) red

19. Cricketers playing a test match wear ______

clothes.

(A) blue (B) black

(C) white (D) red

20. Traditionally umbrellas are ______ in colour.

(A) yellow (B) blue

(C) white (D) black

1.1 Properties of matter

1. The ______ of an object gives an indication of

the amount of matter that an object contains.

2. Matter occupies ______.

3. ______ is made up of very tiny particles.

4. Matter has ______ and ______.

1.2 States of matter

*5. We usually find matter in ______, ______ and

______ forms.

6. The particles in a solid are bound to each other

by a ______.

7. Particles of a solid cannot move much. This is

one of the ______ characteristics of solids.

8. Less viscous liquids ______ easily.

9. Liquefied Petroleum Gas (LPG) cylinders are

used at home and ______ cylinders are used invehicles.

10. ______ spread out to fill the container.

11. ______ can be easily compressed.

1.3 Change of state

*12. On heating, solids get converted to ______

and ______ get converted to gases.

13. ______ describes a physical state of matter.

14. The fourth state of matter is ______.

15. Our body temperature is measured in a unit

called ______.

16. The boiling point of water is ______ C.

1.4 Evaporation, cooling by evaporation,

condensation

17. All liquids can evaporate at ______

temperature under normal air pressure.

18. ______ is the process which creates clouds.

1.5 Sublimation

*19. ______ and ______ are sublimatory

substances.

20. Out of sand and iodine, sand is a ______

substance.


21. ______ enters the object and warms it.

Answers

1. mass 2. space

3. Matter 4. volume, mass

5. solid, liquid, gaseous 6. force

7. physical 8. flow

9. Compressed Natural Gas (CNG)

10. Gases

11. Gases 12. liquids, liquids

13. Phase 14. plasma

15. Fahrenheit 16. 100

17. room 18. Condensation

19. Camphor, naphthalene balls

20. non-sublimatory

21. Heat

1.0 Introduction

1. What is matter?Ans: Anything that occupies space, has mass and

can be perceived through our senses is called

matter.

1.1 Properties of matter

2. What is density?

Ans: Density is the ratio of mass to volume.

Density (d) =Mass(m)

Volume(v)

Fill in the Blanks




4



2. State the characteristics of solids.

Ans: Characteristics of solids:

i. Solids have a definite shape and volume.

ii. Most of the solids are rigid, while some

are elastic.iii. Solids are almost incompressible, i.e.,

their volume and shape is not changed

by external force.

iv. The particles in a solid are closely

packed.

*3. Why do solids have definite shape?

Ans: Solids have definite shape because:

i. The particles of solids are very close to

each other.

ii. The forces holding these particles are

strong.

4. What is elasticity of solids?

Ans: Elasticity of solids:

i. When an external force is applied to a

solid, it undergoes a change in its

volume and shape.

ii. When this external force is removed, the

solid regains its original shape and

volume.

iii This property of solids is known as

elasticity.

Eg. Rubber band, spring, etc.

5. State the characteristics of liquids.Ans: Characteristics of liquids:

i. Liquids have a definite volume.

ii. Liquids flow and have the property of

viscosity.

iii. Liquids cannot be compressed easily.

iv. Liquids do not have a definite shape.

They take the shape of the container in

which they are kept.

6. State the characteristics of gases.

Ans: Characteristics of gases:

i. Gases flow.ii. Gases are highly compressible.

iii. Gases spread everywhere in the

available space.

iv. Gases do not have definite shape and

volume.

#7. It is easier to walk through air than

through water. Why is it so?

Ans: i. Air is in gaseous state and water is in

liquid state.

ii. In air, the particles are so far apart that

the resistance offered by them is

negligible.

iii. In water, the particles are closer than in

air and the resistance offered by them is

more than that of air.

Hence, it is easier to walk through air thanthrough water.

1.3 Change of state

*8. What is the physical state of water at:

i. 257 °C ii. 100 °C

iii. 0 °C

Ans: i. At 257 °C, water is in gaseous state.

ii. At 100 C, water co-exists in liquid and

gaseous state.

iii. At 0 C, water co-exists in the solid

and liquid state.9. Why do temperature of a substance

remains constant while changing from one

state to another?

Ans: i. When substance changes from one state

to another distance between two

molecules get increased.

ii. While changing state heat provided tosubstance is utilised in increasing

distance between the molecules of

substance.

1.4 Evaporation, cooling by evaporation,condensation

10. Why does a desert cooler cools better on a

hot dry day?

Ans: i. On a hot dry day, the temperature is

higher. Thus, there is more dryness in

the surrounding air (i.e. relative

humidity of the air is low).

ii. At a high temperature, rate of

evaporation is more. Thus, a desert

cooler produces more cooling which

results in large fall in the temperature ofits surrounding air.

Hence, a desert cooler cools better on a hot

dry day.

#11. We find dew drops, especially in the early

morning on the leaves. Why?

Ans: i. The temperature of air during the early

morning is generally low.

ii. As the temperature falls, the capacity of

air to hold water vapour becomes less.



Chapter 01: World of Matter

5


iii. During cold nights, the temperature of

air may fall to dew point or below the

dew point.

iv. Thus, excess of water vapour in air

condenses to form drops which falls on

the leaves at night.Hence, we find dewdrops, especially in the

early morning on the leaves.


#12. Why do we paint the outer side of the

container of a solar cooker with black

paint?

Ans: i. In a solar cooker, the food is cooked due

to the heat energy obtained from the

sun.

ii. Black surface absorbs about 98% of the

incident heat radiation that falls on it.

iii. Due to this, the temperature of the solar

cooker increases and the food is cooked

properly.

Hence, we paint the outer side of the container

of a solar cooker with black paint.

#13. Why do cricketers playing test match wear

white clothes?

Ans: i. White clothes reflect most of the radiant

heat falling on them.

ii. Therefore, cricketers do not feel hot

even though it is hot outside.

Hence, cricketers playing test match wear

white clothes.

#14. Traditionally umbrellas are black in colour.

Why are they better than coloured ones?

Ans: i. A black body is a perfect absorber of

heat radiation.

ii. So, the black coloured umbrella absorbsthe heat radiations and does not allow

heat radiations to pass through.

Hence, black umbrellas are better than

coloured ones.

#15. When you go for trekking, which coloured

cap do you prefer to use?

Ans: When I go for trekking, I prefer to use white

coloured cap.

#16. In the state of Rajasthan the temperatures

are very high in summer. Which colour for

the roof is preferable in such regions?

Ans: In Rajasthan, where the temperature is very

high in summer, white colour for the roof is

preferable.

1.3 Change of state

1. Describe the change of phase or change of

state of matter when energy is supplied or

taken away from a substance.

Ans: Change of phase:

i. The phase or state of matter can change

when the temperature changes.

ii. When the temperature is increased, solid

gets converted into liquid and liquid gets

converted into gas.

iii. As the temperature rises, matter moves

to a more active state.

iv. Phase describes a physical state of

matter. Things only move from one

phase to another by physical means.

v. If energy is supplied (like increasing

the temperature or decreasing the

pressure) or if energy is taken away

(like freezing something or increasing

the pressure), a physical change is

created.

*2. The smell of hot sizzling food reaches you

several meters away, but to get the smell

from cold food, we have to go close. Why?

Ans: i. Gases from the hot sizzling food mix

with air easily in the form of vapour.

ii. The molecules of vapour have a lot of

energy. So, these molecules spread

around in all the directions.

+E+E

+E

SolidLiquid

GasPlasma

Each addition of

energy creates achange in state

Answer in brief




6


iii. But molecules of gases from cold food

cannot mix easily with air as molecules

have low energy due to its lowtemperature.

Hence, we have to go close to get the smell

from cold food.

1.4 Evaporation, cooling by evaporation,condensation

3. How does the condensation and

evaporation process keep the earth’s

climate balanced?

Ans: i. Condensation is the formation of liquid

drops from vapour.

ii. It usually occurs when a parcel of rising

air expands and cools.

iii. If it cools enough, some of the water

vapour molecules clump together at a

faster rate.iv. This process creates clouds which

results in rain and snow, causing the

earth’s climate to become cooler.

v. When cloud form heat removed from

the earth’s surface through evaporation

is released again in atmosphere.

1.5 Sublimation

#4. How would you separate the mixture of

sand and iodine crystals?

Ans: i. In the mixture of sand and iodine

crystals, iodine is a sublimatory and

sand is a non-sublimatory substance.ii. By using sublimation method, we can

separate the constituents of this mixture.

iii. Take this mixture in a china dish.

iv. Put an inverted gas funnel over it. Place

a cotton plug in its stem.

v. Heat the china dish. Iodine sublimates

and its vapours get condensed on the

inner side of the funnel and cotton plug.

Sand remain in the china dish.


condensation

1. EvaporationAns: i. Evaporation is the process by which a

liquid gets converted into gaseous form

at any temperature below its boiling

point.

ii. All liquids evaporate at room

temperature and normal air pressure.

iii. In this process, atoms or molecules

escape from the liquid and turn into

vapour.

iv. There are always a few atoms or

molecules with a lot of energy and some

with very low energy.v. The atoms or molecules with lot of

energy are able to build up enough

energy to get converted into gaseous

state.

vi. Once they reach that energy level, they

leave the liquid state. When the atoms or

molecules leave the liquid, we say it has

evaporated.

vii. The rate of evaporation depends upon

the surface area, temperature, humidity,

wind speed, etc.


1. Solids are rigid.

Ans: i. In solids, the particles are closely

packed together and the forces holding

these particles are strong.

ii Solids are almost incompressible.

iii. Their volume is not changed by any

outside force.iv. Their shape remains unchanged even if

an external force is applied.

Hence, solids are rigid.

2. Gases are more compressible than liquids.

Ans: i. In liquids, the distance between the

neighbouring particles is less than those

in the gases.

ii. In gases, the particles spread out to fill

the container.

Inverted funnel

Iodine

China dish

Burner

Cotton plug

Write short notes on

Give scientific reasons




7


iii. The forces of attraction between the

particles are extremely weak in gases,

there are no forces to stop them fromgoing apart but not so weak in liquids.

Hence, gases are more compressible thanliquids.

3. Some liquids like honey flow slowly, while

other liquids such as kerosene flow rapidly.

Ans: i. The differences in flow rate is due to the

property of viscosity.

ii. The viscosity of honey is greater than

that of kerosene.

iii. More viscous a liquid, less is its rate of

flow.

Hence, some liquids like honey flow slowly,

while other liquids such as kerosene flow

rapidly.

*4. A gas exerts pressure on the walls of aclosed container.

Ans: i. In the gaseous state, the particles of a

gas move with a very high speed in alldirections.

ii. As the forces of attraction between the particles of a gas are very weak, they

move fast and collide with the walls of

the container, where a pressure is

created.

Hence, a gas exerts pressure on the walls of a

closed container.

*5. In LPG cylinder, the gas filled is in the

liquefied state.

Ans: i. Gases are highly compressible. They

can be compressed into very small

volumes by applying large pressure.

ii. Gases are liquefied by lowering their

temperature and applying high pressure

where they get compressed. This

process converts the gas into a liquid.

iii. As a result, small LPG cylinders can

contain more gas if it is in liquid form.

Such cylinders can be easily

transported from one place to another.Hence, in LPG cylinder, the gas filled is in the

liquefied state.


condensation

#6. In summer, we wear cotton clothes.

Ans: i. The temperature of the surroundings

becomes very high in summer due to

which we feel hot.

ii. Cotton clothes absorb sweat.

iii. Heat is taken from the body for

evaporation of sweat.

iv. Thus, due to evaporation of sweat body

temperature remains constant.

Hence, we use cotton and light coloured

clothes in summer.

7. The tea in a saucer gets cooled faster than

in a cup.

Ans: i. When we pour very hot tea in a saucer,

it cools quickly due to the process of

evaporation.

ii. Evaporation takes place only at the

surface of a liquid. The rate ofevaporation is directly proportional to

the surface area of a liquid.

iii. The exposed surface area of saucer is

greater than the exposed surface area ofa cup.

Hence, tea poured in a saucer gets cooled

faster than in a cup.

1.5 Sublimation

8. Naphthalene balls disappear over a period

of time, without leaving behind any solid

particles.

Ans: i. Naphthalene balls sublimate at room

temperature.

ii. All its molecules go into vapour phasewithout changing into liquid.

iii. This process takes place when

naphthalene balls absorb heat energy

from the surrounding, which occurs

slowly but continuously.

Hence, naphthalene balls disappear over a

period of time, without leaving behind any

solid particles.

1. The fifth state of matter.

2. The unit which is used to measure the body

temperature.

3. The scientist who discovered the Fahrenheit

scale.

4. A substance which is used as fuel in vehicles.

5. A substance which is used as ideal domestic

fuel in our home.

Name the following




8


Answers

1. Bose-Einstein condensate

2. Fahrenheit

3. Gabriel Daniel Fahrenheit

4. CNG (Compressed Natural Gas)

5. LPG (Liquefied Petroleum Gas)

1. Two objects can occupy the same space at the

same time.

2. When kerosene and water are mixed together,

water will form the upper layer.

3. The particles of a solid cannot move much.

4. Some liquids flow easily as compared to otherliquids.

5. Liquids do not have a definite volume.

6. Gases cannot be compressed easily.

7. It is easier to walk through water than air.

8. Water freezes at 100C.

9. The absorption of energy from the surrounding

reduces the temperature of the surrounding.

10. The rate of evaporation increases with

increase in humidity.

11. Condensation is the process which creates

clouds.

Answers

1. False: Two objects cannot occupy the same

space at the same time.

2. False: When kerosene and water are mixedtogether, kerosene will form the upper layer.

3. True

4. True

5. False: Liquids have a definite volume.

6. False: Gases can be compressed easily.

7. False: It is easier to walk through air than water.

8. False: Water freezes at 0C.

9. True10. False: The rate of evaporation decreases with

increase in humidity.

11. True

1. Water, Kerosene, Sugar, Milk

2. Stone, Common salt, Ice, Oil

3. Sodium, Hydrogen, Oxygen, Nitrogen

4. Sulphur, Phosphorous, Magnesium, Chlorine

5. Camphor, Iodine, Ammonia, Ammonium

chloride

Answers

1. Sugar: Others are liquids.

2. Oil: Others are solids.3. Sodium: Others are gases.

4. Chlorine: Others are solids.

5. Ammonia: Others are sublimatory substances.

1. Solids 2. Rigid solids

3. Elastic solids 4. Liquids

5. Less viscous liquids

6. Higher viscous liquids

7. Gases

8. Sublimatory substances

Answers

1. Blackboard, Ice

2. Stone, Iron

3. Rubber band, Spring

4. Milk, Oil

5. Water, Kerosene

6. Honey, Lubricants

7. Hydrogen, Oxygen

8. Iodine, Camphor

1. Wooden block: Solid :: Milk: …….

2. Stone: Rigid :: Spring: …..

3. Dust: Solid :: Carbon dioxide: ……

4. Solid: Incompressible :: Gas: ..…..

5. Water: Liquid :: Water vapour: ……..

6. The melting point of solid oxygen: 218.4 °C

:: Melting point of glucose: ..…….

7. Boiling point of water: .......... :: Freezing point

of water: 0 °C

8. Ammonium chloride: Sublimatory substance ::Sodium chloride: ……..

Answers

1. Liquid

2. Elastic

3. Gas 4. Compressible

5. Gas 6. 150 °C

7. 100 °C

8. Non-sublimatory substance

State whether the following

statements are true or false,

If false rewrite the correct

statement

T F

Find the odd man out

Give two examples of

Complete the analogy




9


1.

No. Column I Column II

i. Solids a. High compressibility

ii. Liquids b. Incompressible

iii. Gases c. Low compressibility

Ans: (i – b), (ii – c), (iii – a)

2.

No. Column I Column II

i. Solid converts into liquid a. Evaporation

ii. Gas converts into liquid b. Freezing

iii. Liquid converts into gas c. Melting

iv. Liquid converts into solid d. Condensation

Ans: (i – c), (ii – d), (iii – a), (iv – b)

*3.

No.State of

matterA B

1. Gas a. Soil i. Milk

2. Solid b. Kerosene ii. Oxygen

3. Liquidc. Carbon

monoxide

iii. Peas

Ans: (1 – c - ii), (2 – a - iii), (3 – b - i)

1. Solids and Liquids

Solids Liquids

i. Solids have definite

shape.

Liquids do not have

definite shape.

ii. Solids are almost

incompressible.

Liquids are less

compressible.

iii Solids do not flow. Liquids flow.

Eg. Sugar, stone Water, milk

2. Liquids and Gases

Liquids Gases

i. Liquids have

definite volume.

Gases do not have

definite volume.

ii. Liquids have very

low compressibility.

Gases have high

compressibility.

iii Liquids flow upto

certain extent.

Gases flow

everywhere in the

available space.

Eg. Water, kerosene Hydrogen, oxygen

3. Solids and Gases

Solids Gases

i. Solids have definite

shape.

Gases do not have

definite shape.

ii. Solids have definite

volume.

Gases do not have

definite volume.

iii. Solids are

incompressible.

Gases are highly

compressible.

Eg. Table, iron Nitrogen, chlorine

4. Evaporation and Boiling

Evaporation Boiling

i. It takes place at all

temperatures.

It takes place only at

the boiling point.

ii. It causes cooling. It does not cause

cooling.

1. Sample structure of a solid

Ans:

2. Effort needed to compress solid, liquid and

gas

Ans:

More Less

Effort Needed to Compress

GasSolid Liquid

Match the following

Distinguish between the

following pairs

Draw neat & labelled

diagrams of the following




10


3. Condensation due to the expansion of air

Ans:

4. Condensation due to direct cooling of air

Ans:

1. In the following figure water changes into

ice:

a. Which type of change is observed in

the process?

b. For this change of state, is energy

released or absorbed?

Ans: a. Changing of water into ice is a physical

change.

b. In freezing (i.e., in conversion of water

to ice), energy is taken away from water.

So, water releases energy to get

converted into ice.

2. In the following figure, water changes to

hydrogen peroxide:

a. Which type of change is observed in

the process?

b. Is this change reversible?

Ans: a. In the process, chemical change is observed.

b. Changing of water into hydrogen

peroxide is not reversible change.

#1. Classify the following into solids, liquids

and gases: Air, bench, kerosene, bag, bottle,

chalk, brass, water vapour, blackboard,

dust, table, soil, chair, water, door, pen,milk, eraser, petrol, book, windowpanes,

ice, diesel, carbon dioxide, cupboard,

oxygen, mercury.

Ans:

Solids Liquids Gases

Bench, bag, bottle,

chalk, brass,

blackboard, dust,

table, soil, chair,

door, pen, eraser,

book,

windowpanes, ice,cupboard

Kerosene, water,

milk, petrol,

diesel, mercury

Air,

water

vapour,

carbon

dioxide,

oxygen

#2. Suggest one scientific word for all of the

following changes:

i. Solid wax converts into liquid wax.

ii. Ice changes into water.

iii. A plastic bowl kept near the flame,

changes its shape.

iv. Frozen butter is kept outside the

refrigerator.

Ans: Melting

y Activity … II (Textbook page no. 1)

Ans: i. No, we cannot count the number of

particles present in a piece of chalk.

ii. The cotton cloth becomes wet due to

absorption of water.

iii. Yes, we can break the stream of water

with our fingers.

iv. No, it is not possible to fill any more

liquid in the bottle as it is already filled

up to the brim. It is air in the spacewhich was earlier occupied by water.

Activity … III (Textbook page no. 2)

Ans: i. The pebble will sink in water becausethe density of pebble is greater than the

density of water, which is not the case in

plastic spoon.

ii. Dry wood, ice, leaves, kerosene, oil,

etc. are some substances which float on

water.

Water Ice

H2O H2O2

Ice

Water

Liquid water

droplets

Rising air parcel

Activities

Miscellaneous

Questions Based on

Diagrams




11


Activity … IV (Textbook page no. 3 and 4)

Ans: Observation:

i. The liquids come down in the order ofdecreasing speed as follows:

kerosene > water > milk > honey

ii. Among the four liquids, honey is themost viscous and kerosene is the least

viscous liquid.

iii. Kerosene, water and milk take the

shape of the container faster.

iv. Honey forms layers and these layers

take the shape of the container slowly.

Conclusion:

Rate of flow of liquids depends on their

viscosity.

Activity ... V (Textbook page no. 4)

Ans: i. Inflated balloons become heavier than

uninflated balloons because air inside

the inflated balloons also has some

mass.

ii. a. Yes, we get the smell of incense

stick in the other corner. When

an incense stick is ignited, its

material starts burning. The

fragrance present in the incense

stick is gaseous and spreads into

the air in the form of smoke. As

gas molecules move faster thanliquid or solid, they reach from

one corner of a room to the other

corner easily and so a person at

the other corner gets its smell.

iii. Perfume is a volatile substance (easily

escapes into air). Thus, the molecules

of the perfume spread everywhere in

the surrounding air. So, Sabiha can

smell the perfume though she is sitting

in a far off corner.

Activity … VI (Textbook page no. 5)Ans: i. Small droplets of the water are

observed on the inner surface of the lid

because water vapours from the tea get

condensed.

ii. In winter morning, the temperature of

atmosphere is very low. The coconut

oil freezes at this temperature and

becomes solid. In the summer

morning, the temperature of

atmosphere is higher as compared to

winter. Thus, oil does not freeze and

remains in the liquid state.

Activity … VII (Textbook page no. 7)

Ans: i. The wet handkerchief kept in the

open space would dry up faster.

ii. The puddle will reduce in size due to

evaporation of water present in it.

iii. We feel cool at the site where spirit

is applied.

iv. We pour very hot tea in saucer to cool

it rapidly. By doing so, the exposed

surface area increases and the rate of

evaporation also increases which

makes the tea cool faster.

v. a. The water kept in an earthen pot

becomes cool due to the process

of evaporation. b. Large number of pores are

present on the surface of

earthen pot. Water comes out

continuously from these pores

into the outside environment.

c. As a result, evaporation takes

place and the temperature of

water in the pot decreases.

d. Hence, the water kept in an

earthen pot (matka) becomes

cool even in summer.

Activity … VIII (Textbook page no. 8)

Ans: i. Camphor is a sublimatory substance.

It sublimates at room temperature and

changes into gaseous state slowly.

Due to this, camphor becomes smaller

in size and finally disappears.

ii. Naphthalene balls sublimate at room

temperature. They absorb heat energy

from the surrounding and convert into

gaseous form. Naphthalene present in

the gaseous form get mixed with air

due to which bad odour in the toilet

vanishes. So, naphthalene balls are

kept in the toilets.

Activity … IX (Textbook page no. 8)

Ans: Ammonium chloride is a sublimatory

substance. When heated, ammonium

chloride changes into gaseous state without

changing into liquid state. Ammoniumchloride, thus, gets deposited inside the

inverted funnel and on the cotton plug.




12


1. Two vessels contain different types of

liquids A and B. If density of A is two times

that of B and volume of both the liquid

remains same, then which liquid has lessmass?

Ans: B liquid has less mass.

2. X and Y are two substances. They are given

same quantity of heat. X changes its state

from solid to liquid. Y changes its state

from solid to gas.

a. Can X change its state from liquid to

gas when more heat is given?

b. What kind of substance is Y?

Ans: a. If more heat is given, then X can change

its state from liquid to gas.

b. Y is a sublimatory substance.

3. Complete the following chart:

Ans: 1. Solids

2. Liquids

3. Condense into liquids.

Type I: Problems based on

Density(d) =Mass(m)

Volume(v)

#1. What is the density of a wooden block of

mass 4 g and sides 2 cm 3 cm 1 cm?

Ans: Given: m = 4 g, l = 2 cm,

b = 3 cm, h = 1 cm

To find : d = ?

Formula: i. v = l b h

ii. d =m

v

Solution:

From formula (i)

v = 2 cm 3 cm 1 cm

= 6 cm3 From formula (ii)

d =4

6 = 0.67 g/cm3

The density of wooden block = 0.67 g/cm3

2. The mass of an iron block is 150 g and

density is 25 g/cm3. Calculate the volume of

the block.

Ans: Given: m = 150 g, d = 25 g/cm3

To find : v = ?

Formula: d = mv

Solution:

From formula

v =m

d

=3

150g

25g/cm = 6 cm3

The volume of iron block = 6 cm3

3. The density of an object is 30 g/cm3 and its

volume is 8 cm3. Calculate the mass of theobject.

Ans: Given: v = 8 cm3, d = 30 g/cm3

To find : m = ?

Formula: d =m

v

Solution:

From formula

m = d v

= 30 g/cm3 8 cm3

= 240 g

Mass of the object = 240 g

Type II: Problems based on (F 32) 5

9= C

4. The temperature of an object is 20 °C.

Express this temperature in Fahrenheit.

Ans: Given: Celsius temperature (C) = 20 °C

To find : Fahrenheit temperature (F) = ?

Formula: (F 32)

5

9= C

Melt into

liquids.

Sublimate into

gases.

Matter

Gases

can be converted

into

Evaporate into gases.

Freeze into solids

can be converted

into1 2

3

HOTS

Solved Examples




13


Solution :

From formula

5F = 9C +160

5F = 9 20 +160

= 180 +160

= 340

F =340

5 = 68 F

Temperature in Fahrenheit = 68 F

5. The temperature of an object is 95 F.

Express this temperature in Celsius.

Ans: Given: Temperature in Fahrenheit (F) = 95 F

To find : Temperature in Celsius (C) = ?

Formula: (F 32) 5

9 = C

Solution:

From formula

C = (95 32) 5

9

= 63 5

9

= 7 5

= 35 °C

Temperature in Celsius = 35 C

Type I

1. The mass and volume of an object are 50 g

and 25 cm3 respectively. Calculate the density

of that object.

2. The volume and the density of an object is 18

cm3 and 4 g/cm3 respectively. Calculate the

mass of that object.

3. Find the volume of an object having mass 27 g

and density 3 g/cm3.

Type II

4. Express the following temperature in

Fahrenheit.

i. 45 °C ii. 60 °C

iii. 15 °C iv. 70 °C

5. Express the following temperature in Celsius.

i 104 °F ii. 122 °F

iii. 194 °F iv. 50 °F

1. 2 g/cm3

2. 72 g

3. 9 cm3

4. i. 113 °F ii. 140 °Fiii. 59 °F iv. 158 °F

5. i. 40 °C ii. 50 °C

iii. 90 °C iv. 10 °C

Practice Problems

Answers to Practice Problems

science and technology std 9th

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