cbse cbse class 10 science solved question paper 2010 set 1

CBSE Class 10th Science Solved Question Papers 2010 www.jargranjosh.com

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Solved Question Paper 2010Subject: Science

Class: XSet: I

Time Allowed: 3Hours Maximum Marks: 70

General Instructions:

(i) All questions are compulsory.

(ii) The question paper consists of 34 questions divided into four sections A, B, C and D.

Sections A contains 8 questions of one mark each, which are MCQs Section B contains 6 questions of two marks each Section C contains 10 questions of three marks each Section D contains 10 questions of four marks each.

(iii) Use of calculators is not permitted



SECTION A1. What changes in the colour of iron nails aid copper sulphate solution do you observe after keeping the iron nails dipped in copper sulphate solution for about 30 minutes?

Solution:

Iron nail kept in the copper sulphate solution displays displacement reaction, where iron is

removed by copper of copper sulphate solution.

Reaction:

Fe(s) + CuSO4(aq) FeSO4(aq) + Cu(s)

(Copper sulphate) (Iron sulphate)

2. State two characteristic features of carbon which when put together give rise to a largenumber of carbon compounds?

Solution:

The two most important characteristics feature that makes it source of many carbon

compound, characteristics - tetravalency and catenation.

3. Explain why a ray of light passing through the centre of curvature of concave minor gets

reflected along the same path.

Solution:

The light falling on the centre of curvature is reflected back along the same path because

incident ray falls on the mirror along the normal to the reflecting surface.



4. What is the nature of the image formed by a concave mirror if the magnification produced

by the minor is +3?

Solution:

The image will be a minute structure reducing its size to 3 times, of its original structure will

be virtual and erect.

5. A charged particle enters at right angles into a uniform magnetic fieldas shown. What

should be the nature of charge on the particle if itbegins its interaction with the magnetic

field.

Solution:

According to Flemings left hand rule the direction of current where force is perpendicular to the direction of magnetic. In the given figure direction of current is taken opposite to the

direction of motion of electrons. The force is therefore directed into the page

6. Name the part of our eyes that helps us to focus near and distantobjects in quick succession.

Solution:

Eye lens, helps us to see the object clearly either object is near or distant.



7. What happens when an aqueous solution of sodium sulphate reacts withan aqueous

solution of barium chloride? State the physical conditionsof reactants in which the reaction

between them will to take place.Write the balanced chemical equation for the reaction and

name the type of reaction.

Solution:

When aqueous solution of sodium sulphate reacts with aqueous barium chloride it results in

formation of barium sulphate (BaSO4) along with the formation of white precipitation,

visualized physically. Such type of reaction involves displacement of two molecules so called

as double displacement reaction.

Reactions which form white precipitation are called precipitation reaction, these are insoluble components.

Na2SO4(aq) + BaCl2(aq) BaSO4(s) + 2NaCl(aq)

(Sodium sulphate) (Barium chloride) (Barium sulphate) (Sodium chloride)

8. What is the main constituent of biogas? How is biogas obtained from biomass? Write anytwo advantages of using this gas.

Solution:

Two major constituents of biogas is cow-dung and water

Obtaining biogas from biomass:

Biogas is produced by decomposing cow dung, vegetable waste, sewage and plant residue

after harvesting in a dome like structure without the presence of oxygen, it is popularly

known as gobar-gas. Mixture of cow-dung and water is fed into a closed chamber fordigestion by anaerobic micro-organism which generates methane, carbon dioxide, hydrogen

and hydrogen sulphide.

Advantages of biogas:

a) Excellent fuel as it contains up to 75% methane



b) It burns without smoke, leaves no residue like ash in wood, charcoal and coal burning.

c) Slurry left behind can be used periodically in fields as excellent manure, rich in

nitrogen and phosphorous

9. In the figure given below a narrow beam of white light is shown to passthrough a

triangular glass prism. After passing through the prism itproduces a spectrum XY on a

screen?

a) State the colour seen at X and Y.

b) Why do different colours of white light bend through different anglesWith respect to

the incident beam of light?

Solution:

a) Colour observed is red and violet.

b) Light entering the prism gives different coloured of light bend through different angle

when an incident ray through it, as the colour bands are produced at different bends.

10. What is a solenoid? Draw the pattern of magnetic Field lines of a solenoid through which

a steady current flows. What does the pattern of field lines? Inside the solenoid indicate?



Solution:

Solenoid can be defined as a coil of many circular turn of insulated copper wire wrapped in

cylindrical structure. The lines inside the solenoid are parallel and straight, indicating uniform

magnetic field. Strong magnetic field inside the solenoid can be used for magnetizing soft

iron when placed inside the coil.

Figure: Movement of magnetic field inside the solenoid

11. A coil of insulated wire is connected to a galvanometer. What would beseen if a bar

magnet with its north pole towards one face of the coil is

(i) Moved quickly towards it,

(ii) Moved quickly away from the coil and

(iii) Placed near its one face?

Name the Phenomena involved.

Solution:

`



(i) Movement of needle (galvanometer) toward right indicate the flow of current from AB, as

the motion in magnets stops deflection becomes zero.

(ii) Withdrawal of North Pole away from coil leads to the deflection of galvanometer to the

left, indicating flow of current in opposite direction.

(iii) Magnet kept near the face, the deflection of the galvanometer drops to zero.

This phenomenon is called Electromagnetic Induction

12. Mention any four limitations in harnessing wind energy on a large scale.

Solution:

1. Continuous blowing of air is required to develop wind energy farms

2. Wind speed should be higher than 15 km/h to maintain the speed of the turbine.

3. Back-up facilities have is important during a period when there is no wind.

4. For preparing 1 MW generator wind farm we need about 2 hectares of land.

13. At what distance should an object be placed from a convex lens of focal Length 18 cm to

obtain an image at 24 cm from it on the other side. WhatWill be the magnification produced

in this case?

Solution:

Given that,

Focal length f = 18

Image distance v =24

From the lens formula, 1/v 1/u = 1/f (where u = object distance)

or 1/u =1/v 1/f



= 1/24 1/18

= 1/6

or u= 6

Magnification is given by m = v/u

= 24/( 6)

= 4

The object must be placed 18 cm away from the lens, on the other side to produce a

magnification of 4.

14. No chemical relation take place when granules of a solid. A, are mixed withthe powder of

another solid. B However when the mixture is heated, a reaction takes place between its

components. One of the products, C, is ametal and settles down in the molten state while the

other product. D. floatsover it. It was observed that the reaction is highly exothermic.

(i) Based on the given information make an assumption about A and B and write a chemical

equation for the chemical reaction indicating theconditions of reaction indicating the

conditions of reaction. Physicalstate of reactants and products and thermal status of reaction.

(ii) Mention any two types of reactions tinder which above chemical reaction can be

classified. 3

Solution:

(i) Suppose that solid A is MnO2 while solid B is Aluminium (Al), on mixing and heating the

mixture of solid A & B, manganese (Mn) is formed in liquid state and aluminium oxide

(Al2O3) floats freely. Formation of Mn release extensive heat energy so called as exothermic

reaction.

Equation: 3MnO2 (s) + 4Al (s) 3Mn (l) + 2Al2O3 (s) + Heat



(ii) Reaction mentioned above can be classified as

a) Redox reaction

b) Displacement reaction

OR

Name the functional group of organic compounds that can be hydrogenated. With the help of

suitable example, explain the process of hydrogenation mentioning the condition of the

reaction and any one change in physical property with the formation of the product. Name

any one natural source of organiccompounds that are hydrogenated.

Solution:

Alkenes and Alkynes

Saturated hydrocarbon can be produced by adding hydrogen withunsaturated hydrocarbons in

the presence of nickel. The reaction is completed by using nickel acts as a catalyst.

On hydrogenation, unsaturated fatty acid which is liquid at room temperature will change into

solid and saturated, after completing reaction.

Vegetable oil is a Natural source of organic compound that is hydrogenated.

15. Atoms of eight elements A. B. C. D, E, F. G and H have the same number ofelectronic

shells but different number of electrons in their outermost shell. Itwas found that elements A

and G combine to form an ionic compound. Thiscompound is added in a small amount to

almost all vegetable dishes duringcooking. Oxides of elements A and B are basic in nature



while those of E andF are acidic. The oxide of D is almost neural. Based on the above

information answer the following questions :

(i) To which group or period of the periodic table do the listed elements belong?(ii) What would be the nature of compound formed by a combination of elements B and F?(iii) Which two of these elements could definitely by metals?

(iv) Which one of the eight elements is most likely to be found in gaseous state at room

temperature?

(v) If the number of electrons in the outermost shell of elements C and G3and 7 respectively,

write the formula of the compound formed bythe combination of C and G.

Solution:

a) The listed chemicals belong to third period; it includes Na, Mg, Al, Si, P, S, Cl& Ar.

b) Compound formed by the combination of B (Mg) and F (S) will result in formation of

salt called MgSo4

c) Compound A (Na) and B (Mg)

d) Element H (Ar), is found in gaseous state in room temperature.

e) They will form Alcl3 (Aluminium chloride)

16. Write the names and symbols of two most reactive metals belonging to group IThe

periodic table. Explain by drawing electronic structure how either one ofthe two metals reacts

with a halogen. With which names the bond formedbetween these elements known and what

is the class of the compound soformed known? State any four physical properties of such

compounds.

Solution:

Two most reactive metals of group 1 are oxygen and sodium.



Electronic configuration of these metals resembles alkali metals.

H =1

Li =1,2

Na = 1,8,2

K = 1,8,8,2

Like halogen hydrogen, oxygen and sodium can form similar structure as halogen.

These molecule forms ionic bond, forming salts.

a) Physical property of group 1 compounds

b) They are soft and so can be cut with knife

c) They are very reactive, with higher melting and boiling point.

d) NaCl exist in the form of salt.

e) They have to be preserved under control condition, for Ionic compounds are soluble

in polar solvents (water) and insoluble in non-polar or organicsolvents (kerosene and

petrol).

OR

What is meant by refining f metals? Name the most widely used method of refining impure

metals produced by various reduction processes .Describe withthe help of a labelled diagram

how this method may be used for refining of copper.



Solution:

Metals which are refined differently depending upon the reactivity. Metals which are very

reactive can be obtained by electrolytic reduction which involves oxygen e.gsodium,

magnesium, calcium,aluminium, etc.

Most important method for refining impure metals is electrolytic refining; this process is used

to refine copper, zinc, nickel, silver, gold etc. Here impure metal is kept in anode while a thin

section of pure metal is kept at cathode dipped in electrolytic solution. On passing the current

pure metal from anode starts to dissolve in the solution, subsequently gets deposited on

cathode, while the impurity remains dissolved into the solution while solid impurity remain

settled at the bottom, the anode mud.

Figure: Electrolytic refining of copper.

17. Derive the expression for the heat produced due to a current I flowing for a time intervalt through a resistor R having a potential difference V acrossits ends. With which name isthe relation known? How much heat will aninstrument of 12W produce in one minute if it is

connected to a battery of 12 V.



Solution:

Lets consider current I flowing through resistance R, potential difference across is V, t istime during the charge Q flowing across.

Work done for moving Q through V = VQ

The power input in t time is = VQ/t =VI

Energy supplied to the circuit by the source in time t is P * t,i.eVIt

For steadycurrent I, the amount of heat H produced in time t is H= VIt

Using ohms law the equation H = I2RtThis is known as Joules law of heating.

Numerical: We know H = I2Rt, H can be written as P * t

So, H = 12 * 60 = 720 J

OR

Explain with the help of a labelled circuit diagram how you will find theresistance of a combination of three resistors, of resistance R1, R2 and R3 joined in parallel. Also mention how you will connect the ammeter and the voltmeter in the circuit when measuring the current in the circuit and the potential difference across one of the threeresistors of the combination.

Solution:

Figure: R1, R2, R3 with voltmeter and ammeter

Total current I, is equal to the sum of all the separate currents through each branch of thecombination.

I = I1 + I2 + I3

Lets assume that resistance Rp be the equivalent resistance of the parallel combination ofresistors.

Using Ohms law to the parallel combination of resistors, and to each resistor



I = V/Rp

I1 = V /R1; I2 = V /R2; and I3 = V /R3

V/Rp = V/R1 + V/R2 + V/R3

or 1/Rp = 1/R1 + 1/ + 1/R3 (12.18)

It is conclude that reciprocal of the equivalent resistance of a group of resistances joined in parallel is equal to the sum of the reciprocals of the individual resistances.

In parallel combination XY connect the circuit with battery, key and ammeter while putvoltmeter in parallel to the resistors.For calculating individual resistance plug ammeter andvoltmeter from circuit, insert ammeter in series with resistance R1 as given in figure and notereading in ammeter I1.

Figure: Checking the individual resistance

19. Name the green dot like structures in some cells observed by a student when aleaf peel

was viewed under a microscope. What is this green colour due to?

Solution:

Green dots appearing on the leaf peels is cellular organelles called chloroplasts which contain

chlorophyll, the green colour is due to the presence of chlorophyll.

20. How is the spinal cord protected in the human body?

Solution:

Spinal is protected by a hard bumpy structure called the vertebral column orcommonly called

as backbone in the back side of body.



21. How is the increasing demand for energy adversely affecting our environment?Solution:

The burning fossil fuels cause air pollution on burning; in some cases assembly of solar

device may result in environmental damage however the release of water from hydroelectric

power plant may cause death of fishes and animals in water.

22. What are hormones? Name the hormone secreted by thyroid and state its function.

Solution:

Hormones are the chemical messenger that brought about changes in body; coordinate proper

body function, development of sexual characters etc. they may act locally or distantly

depending upon there function. Thyroid secrets thyroxinhormone for carbohydrate, fat and

protein metabolism, while Iodine is essential for thyroxin synthesis.

23. With the help of diagrams show the different stages of binary fission in Amoeba.

Solution:

Figure: Reproduction of Amoeba



24. Give one example each of characters that are inherited and the ones that are acquired in

humans. Mention the difference between the inherited and the acquired characters.

Solution:

Example

a) Mendel performed an experiment by crossing tall and dwarf plant, in F1 generation all

the plants were tall while in F2 quarter of plants were short, indicate that tallness and

dawrfness was inherited from parental character.

b) Change in the weight of beetels because of starvation doset transfer the gene to next generation.

Difference

Inherited characters get incorporated with change in DNA sequence, with formation of new

proteins causing harm to human body, while acquired character are not incorporated with

DNA.

25. Write the full form of DNA. Name the part of the cell where it is located.Explain its role

in the process of reproduction of the cell.

Solution:

DNA (Deoxy-ribo Nucleic Acid)

The DNA is located in the nucleus of a cell.

It acts as an information source for making proteins

26. Explain the phenomenon of biological magnification. How does it affectorganisms belonging to different tropic levels particularly the tertiary the tertiary consumers? 3



Solution:

Biological magnification is the process of accumulation of harmful chemicals in the body

tertiary consumers.

Autotrophs are responsible for producing food with the help of sunlight and it absorbs

nutrients, water and minerals which is available for heterotrophs as secondary consumer

through food chain, which is then eaten up by tertiary consumer the human being. The

chemicals gets accumulated at each level.

27. Explain the process of digestion of food in mouth, stomach and small intestine in human body.

Solution:

Mouth

Human being at hungry state eats various kinds of food so that hunger can be minimized.

Whatever food we eat it has to be processed and crushed into small particle by teeth for

proper absorption of minerals and movement of food in the food pipe. The food we eat gets

mixed with saliva released from salivary gland which contain essential enzyme called

salivary amylase which mainly involves the breakdown of starch, a complex mixture of

sugar. Food mixed with saliva is then passed to the stomach for further digestion by the

process called peristalsis.

Stomach

The food then moves to the stomach where muscular wall helps in mixing of food with more

digestive juice secreted by gastric glands present in its walls. It release hydrochloric acid and

creates acidic medium helping pepsin to function properly. Food is then forwarded to small

intestine by a pour guarded by sphincter muscles.

Small intestine



It is the longest part of alimentary canal, which is compacted in such a way that it doesntlooks like the longest part of alimentary canal. It is the site for digestion of carbohydrate,

protein and fats; it also receives secretion from liver and pancreas. Here bile juice degrade the

fat droplets by emulsification, finally enzymes convert theproteins to amino acids, complex

carbohydrates into glucose and fats into fatty acids and glycerol.

OR

(a) List the three events that occur during the process ofphotosynthesis. Explain the role of

stomata in this process.

(b) Describe an experiment to show that sunlight is essential for photosynthesis.

Solution:

(a) Three most important steps of photosynthesis is-

i. Absorption of light energy by chlorophyll

ii. Conversion of light energy to chemical energy and splitting of water molecules into

hydrogen and oxygen

iii. Reduction of carbon dioxide to carbohydrates

Stomata are present in enormous amount over leafs, this tiny pores helps in the exchange of

gaseous by photosynthesis. Since large amount of water can also be lost through these

stomata, the plant closes these pores when it does not need carbon dioxide for photosynthesis,

opening and closing of pours is regulated by guard cells, it swell up when water flows inside

them, causing the stomatal pore to open. Similarly the pore closes if the guard cells shrink.

(b) Experiment to prove that sunlight is essential for photosynthesis

i. Select two healthy plants.

ii. Keep them in a dark room for 3 days.

iii. Now place them in different air tight chambers, one supplied with potassium

hydroxide, which is used to absorb carbondioxide.

iv. Now keep the plants in sunlight for 2 hr.



v. Pluck leaf from both plants and check the presence of starch.

vi. Higher starch content in the jar with potassium hydroxide indicate that in the presence

of light the photosynthesis have occurred so higher starch content is found.

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