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Paper 1

SUMMATIVE ASSESSMENT –I

SCIENCE (Theory)

Class – X

Time allowed: 3 hours Maximum Marks: 90

General Instructions: a) All questions are compulsory. b) The question paper comprises of two sections, A and B. You are to attempt both the sections. c) Questions 1 to 3 in section A are one mark questions. These are to be answered in one word or in one sentence. d) Questions 4 to 6 in section A are two marks questions. These are to be answered in about 30 words each. e) Questions 7 to 18 in section A are three marks questions. These are to be answered in about 50 words each. f) Questions 19 to 24 in section A are five marks questions. These are to be answered in about 70 words each. g) Questions 25 to 27 in section B are 2 marks questions and Questions 28 to 36 are multiple choice questions based on practical skills. Each question of multiple choice questions is a one mark question. You are to select one most appropriate response out of the four provided to you.

Section A

1.

Define Electrolysis.

2.

What is breathing?

3.

A wire of resistance 10 Ω is bent in the form of a closed circle. What is the effective resistance between the two points at the ends of any diameter of the circle?

4.

A calcium compound which is a yellowish white powder is used as a disinfectant and also in textile industry. Name the compound. Which gas is released when this compound is left exposed to air?

5.

Name the ovarian hormones and give the function of any one of them.

6.

What is the difference between direct and alternating currents? Write one important advantage of using alternating current.

7.

Balance the chemical equation:

(a) Cu + H

2

SO

4

---------------------



CuSO

(b) Na + Cl

2

-------------------------



NaCl

4

+ H

2

(c) KClO

3

-------------------------



KCl + O

2

8.

Write one equation each for decomposition reactions where energy is supplied in the form of heat, light or electricity.

9.

(i) Differentiate between ‘strong’ and ‘weak’ electrolyte.

Select the strong electrolytes from amongst the following: Molten NaCl, glacial CH3COOH, strong

NH4OH solution, dil. HCl

10.

Give reasons:

(a) Germanium is called a metalloid.

(b) Zirconium is known as a strategic metal.

(c) Nitrogen in used to preserve food.

11.

(a) What are strategic metals? Give one example also.

(b) State the reason for the following behaviour of Zinc metal:

On placing a piece of Zinc metal in a solution of mercuric chloride, it acquires a shining silvery surface but when it is placed in a solution of magnesium sulphate no change is observed.

12.

What is the function of epiglottis in man? Draw a labelled diagram showing the human respiratory system.

13.

Draw a diagram of the front view of human heart and label any six parts including at least two, that are concerned with arterial blood supply to the heart muscles.

14.

Draw the diagram of a neuron.

15.

In a household 5 tubelights of 40 W each are used for 5 hours and an electric press of 500 W for 4 hours everyday. Calculate the total electrical energy consumed by the tubelights and press in a month of 30 days.

16.

Aslam is a welder by profession who was working at Mohan’s house. After making a ‘railing’ by using electric welding with naked eyes, Aslam was using a grinder on it to smoothen the welding joints. Just them some particles fell into Aslam’s eye. He started crying with pain. Mohan hired an auto and took him to an eye hospital, doctor used a device connected to two electric wires to remove the particles form Aslam’s eye. Aslam asked Mohan what had fallen into his eye and what device was used by the doctor to remove that particle from the eye. Being a science student of class X,

Mohan explained everything to Aslam and asked him to be careful in future.

Read the above passage and answer the following questions:

(a) What could be the particle fell into Aslam’s eye?

(b) What device was used by the doctor to remove the particle and how it worked?

(c) What values are shown by Mohan during this episode?

[Value Based Question]

17.

Explain the difference between nuclear fission and nuclear fusion reaction with examples. Give reason why the energy due to fusion is not being used to meet our day to day energy needs?

18.

With the help of a labelled diagram, describe the working of a solar water heater.

19.

With the help of an activity, explain that hydrogen and oxygen are released when electric current is passed through water.

Or

(a) Crystal of copper sulphate are heated in a test tube for some time:

(i) What is the colour of copper sulphate crystals before heating and after heating?

(ii) What is the source of liquid droplets seen on the inner upper side of the test tube during the heating process?

(b)

A metal ‘X’ when dipped in aqueous solution of aluminiumsulphate no reaction is observed whereas when it is dipped in an aqueous solution of ferrous sulphate, the pale green solution turns colourless. Identify the metal ‘X’ with reason.

20.

(i) Define the term alloy and amalgam. Name the alloy used for welding electric wires together. What are its constituents.

(ii) Name the constituents of the following alloys:

(a) Brass (b) Stainless steel (c) Bronze

State one property in each of these alloys, which is different from its main constituents.

Or

What method of concentration of ore is preferred in each of the following cases and why?

(i) The ore has higher density particles interspersed with a large bulk of low density impurities.

(ii) The ore consists of copper sulphide intermixed with clay particles.

(iii) Give an example of amalgam.

21.

(i) Name the blood vessel that brings oxygenated bloof to human heart.

(ii) Which chamber of human heart receives oxygenated blood?

(iii) Explain how oxygenated blood from this chamber is sent to all parts of the body.

Or

(i) Name the blood vessel that brings deoxygenated blood to human heart.

(ii) Which chamber of human heart receives deoxygenated blood?

(iii) Explain how deoxygenated blood from this chamber is sent to lungs for oxygenation.

22.

(a) Name an instrument that measures electric current in a circuit. Define the unit of electric current.

(b) What do the following symbols represent in a circuit diagram:

(c) An electric circuit consisting of a 0.5 m long Nichrome wire XY, an ammeter, a voltmeter, four cells of 1.5 V in series each and a plug key was set up.

(i) Draw the electric circuit diagram to study the relation between the potential difference maintained between the points X and Y and the electric current flowing through XY.

(ii) Following graph was plotted between V and I values using above circuit:

What would be the values of

V

ratios when the potential difference is 0.8 V, 1.2 V and

I

1.6 V respectively? What conclusion do you draw from these values?

Or

Explain the following:

(i) Why is the tungsten used almost exclusively for filament of an electric lamp?

(ii) Why are the elements of electric heating devices, such as bread-toaster and electric irons, made of an alloy rather than a pure metal?

(iii) Why is the series arrangement of appliances not used for domestic circuits?

(iv) How does the resistance of a wire vary with its area of cross-section?

(v) Why are copper and aluminium wires usually employed for electric energy transmission?

23.

What is electromagnetic induction? Give two methods of inducing electric current in a coil. Explain each method with the help of diagram.

Or

Draw a labelled diagram of domestic circuit. What is the importance of earthing in a circuit?

24.

State the principle on which an electromagnet works. Describe an activity to make an electromagnet.

Give two uses of electromagnet.

Or

Describe an activity to draw magnetic lines of force around a current carrying (a) straight conductor,

(b) circular loop.

Section B

25. Which of the following gas turn limewater milky:

(a) CO2 (b) SO2

(c) Both CO2 and SO2 (d) Neither CO2 nor SO2

Write chemical reactions involved.

26.

A student wanted to decolourise a leaf. In which solvent, he should boil the leaf? Justify your answer.

27.

The current flowing through a resistor connected in an electrical circuit and the potential difference developed across its ends is shown in figure. Calculate the value of resistance of the resistor in ohms.

28.

Given below are the observations reported by four students I, II, III and IV for the changes observed with dilute HCl or dilute NaOH and different materials.

Material DilHCl Dil. NaOH

I. Moist litmus paper Blue to red Red to blue

Zinc metal

III. Zinc metal on heating

React at room temperature

Liquid becomes milky

IV. Solid sodium bicarbonate No reaction

Does not react at room

Temperature

Remains clear and

Transparent

Brisk effervescence

The incorrectly reported observation is:

(a) I (b) II (c) III

29.

Dil. H2SO4 cannot be used in preparation of SO2 because:

(a) It is not a good oxidizing agent.

(d) IV

(b)

I.

It is a good reducing agent.

(c) It is bleaching agent.

(d) It is dehydrating agent.

30.

A student asked to demonstrate the following two properties of sulphur dioxide gas:

It is heavier than air and

II.

It is highly soluble in water.

Which two of the following four arrangements would the student use to demonstrate these properties:

(a) I and II (b) II and III (c) I and III (d) II and IV

31. Medulla Oblongata is originated from:

(a) Mesoderm (b) Ectoderm

32. The innermost layer of the human eye is:

(b) cornea (a) sciera

(c) Endoderm

(c) retina

(d) Ectomesoderm

(d) lens

33.

In the experiment on studying the dependence of current (I) on potential difference (V), four student set up their circuits as shown below:

The best set up is that of:

(a) student I (b) student II (c) student III (d) student IV

34.

The following circuit diagram shows the experimental set-up for the study of dependence of current on potential difference. Which two circuit components are connected in series:

(a) Battery and Voltmeter (b) Ammeter and Voltmeter

(c) Ammeter and Rheostat (d) Resistor and Voltmeter

35.

For a current in a long straight solenoid N and S-poles are created at the two ends. Among the following statements, the incorrect statement is:

(a) The field lines inside the solenoid are in the form of straight lines which indicate that the magnetic field is the same at all the points inside the solenoid.

(b) The strong magnetic field produced inside the solenoid can be used to magnetize a piece of magnetic material like soft iron, when placed inside the coil.

(c) The pattern of magnetic field associated with the solenoid is different from the pattern of the magnetic field around a bar magnet.

(d) The N and S-poles exchange position when the direction of current through the solenoid is reversed.

36.

Which is the ultimate source of energy:

(a) Water (b) Sun (c) Uranium (d) Fossil fuels


SCIENCE (Theory)

Class – X

(Solutions)

SECTION-A h) Electrolysis is a process in which a compound is broken down in simpler substance whenelectric current is passed through it in motion state or in aqueous solution. i) The process of letting in oxygen from air into the lungs and carbon dioxide out of the lungs is called breathing. j) Two points at the ends of any diameter will divide the resistor into two equal parts. So parts are in parallel combination.

1 1 2 5

 1

   ⇒ R eq

  2.5  eq

5 5 5

10.

Bleaching powder (Calcium oxychloride)

Chlorine gas is released.

2

CaOCl

2

+ CO

2

 CaCO

3

+ Cl

2

(g)

5.

The hormones secreted by ovaries are estrogen and progesterone.

At puberty, estrogens stimulate the growth, maturation and functions of female secondary sex organs such as uterus, fallopian tubes and the duct system of mammary glands.

6.

Difference between direct and alternating current:

Direct current always flows in one direction only whereas alternating current reverses its direction periodically.

Advantage of an alternating current:

(a)

(b)

(c)

R

Alternating current can be transmitted over a long distances without loss of energy.

7. Cu + H

2

SO

4

---------------------



CuSO

4

+ H

2

2Na + Cl

2

-------------------------



2NaCl

2KClO

3

-------------------------



2KCl + 3O

2

8 (a) CaCO

3

 s

  heat

CaO

 s



+ CO

2

 g



(b) 2AgCl

(c) 2H

2

O



 s

  Sunlight

2Ag

 s



+ Cl l

  electricity  2H

2

 g



+ O

2

2

 g



 g



9(i) Strong electrolytes are those which dissociate into ions completely in aqueous solution. Weak electrolytes are those which do not associate into ions completely in aqueous solution.

(ii) CH

3

COOH and NH

4

OH are weak electrolytes whereas molten NaCl and dilute HCl are strong electrolytes.

13.

10.

(a) Germanium shows the properties of both metals and non-metals, therefore, it is regarded as metalloids.

(b) Zirconium is highly valuable for economy for country as it is very useful in nuclear reactor, therefore it is called a strategic metal.

(c) Nitrogen prevents food from getting oxidized, therefore, it is used to preserve food.

11.

(a) Strategic metals are those which are very important for the economy or defence of a country. These metals and their alloys are used in atomic energy, space science projects, jet engines, high grade steels, etc., e.g., Titanium, Zirconium, Chromium, Manganese etc.

(b) When Zinc metal is placed in solution of mercuric chloride, Zn displaces mercury and a shining silvery surface is formed because zinc is more reactive than mercury.

Zn

 s



+ HgCl

2

 aq

  ZnCl

2

 aq



+ Hg

 l



When zinc metal is placed in MgSO

4

solution, no reaction takes place because Zn is less reactive than Mg, therefore it cannot displace Mg from MgSO

4

.

12.

The function of epiglottis in man is that at the time of swallowing food, the epiglottis closes the tracheal opening thereby preventing the food from entering the windpipe.

14.

15. Energy consumed by 5 tubelights of 40 W for 5 hours in 1 day = 5 

40

 5 = 1 kWh

Energy consumed by an electric press of 500 W for 4 hours in 1 day =

1000

500  4

= 2 kWh

1000

Energy consumed in 1 day = 1 + 2 = 3 kWh

 Total electrical energy consumed in 30 days = 3 x 30 = 90 kWh = 90 units

16.

(a) An iron particle fell into Aslam’s eye while using the grinder on iron railing.

(b) The doctor used an electromagnet to remove the tiny iron particle. Electromagnet is a powerful magnet and the iron particle in the eye is strongly attracted by the electromagnet, sticks to the electromagnet and gets removed.

(c) Mohan showed the values of (i) Ability to handle a serious situation with calmness and (ii)

Desire to help others (by rushing Aslam to an eye hospital).

17.

Difference between Nuclear fission and Nuclear fusion:

Nuclear Fission Nuclear Fusion

(i) Heavy nucleus splits to form lighter nuclei.

(ii) Products are radioactive.

(iii) Energy released to nearly 200 MeV.

(iv) Energy per nucleon is less.

(i) Lighter nuclei fuse together to form heavy nucleus.

(ii) Products are non-radioactive.

(iii) Energy released to nearly 21.6 MeV.

(iv) Energy per nucleon is more.

Example:

Fission:

Fusion:

235

92

U +

1 n 

0

139

56

1

2 H +

1

2 H  4

2

Ba + 94

36

Kr + 3

He + Energy

0

1 n + Energy

Fusion is not used to meet day-to-day energy requirements because it is not controlled so far, and it can be self sustained only at 10 8 K temperature.

18.

Solar water heater: It is a device in which water is heated by using solar energy.

Principle: Solar water heater works on the heat absorbing property of balck surfaces and greenhouse effect.

It consists of an insulated box B which is painted black from inside and in which copper tube is fitted in the form of a coil. These copper tubes are painted black from outside so that they may absorb hot rays of the sun more efficiently. The box is covered with glass lid so as to prevent heat loss by convection and radiation. The two ends of the copper tube of solar water heater are joined to the water storage tank.

19.

Activity

(i) Take a plastic vessel. Drill two holes at its bottom and set rubber stoppers in these holes.

(ii) Insert carbon electrodes in these rubber stoppers and connect these electrodes to a 6 volt battery and a switch.

(iii) Fill the vessel with water such that the electrodes are immersed. Add a few drops of dilute sulphuric acid to the water in the vessel.

(iv) Take two graduated test tubes filled with water and invert them over the two carbon electrodes.

(v) Switch on the current.

(vi) After sometime you will observe the formation of bubbles at both the electrodes. These bubbles displace water in the graduated tubes.

(vii) Once the test tubes are filled with the respective gases, remove them carefully.

(viii) Test these gases one by one by bringing a burning splinter of wood close to the mouth of the test tubes.

(ix) When the glowing splinter of wood is brought close to the mouth of one test tube, it relights and when it is brought close to the mouth of other test tube, the gas burns with a pop. Oxygen is the only common gas that relights the splinter and hydrogen gas buns with a pop.

Or

(a) (i) Blue; white

(ii) The liquid droplets are actually the water droplets. The source of water droplets is the water of crystallization of hydrated copper sulphate crystals



CuSO

4

.5H

2

O



.

(b) When metal ‘X’ is dipped in aqueous solution of aluminiumsulphate no reaction is observed, it means it is less reactive than aluminium. But when it is dipped in ferrous sulphate solution, the solution turns form pale green to colourless, so ‘X’ is more reactive than iron and thus displaces it from its solution.

Therefore, ‘X’ must be Zinc. It reacts with ferrous sulphate to form colourless zinc sulphate solution by displacing iron.

Zn

 s



+ FeSO

4

 aq

  ZnSO

4

 aq



+ Fe

 s



20. (i) Alloy is homogeneous mixture of two or more metals. One of them can be a non-metal also.

Amalgam is an alloy of any metal with mercury.

Solder is an alloy used for welding electric wire together. It contains lead (Pb) and tin (Sn)

(ii) (a) Brass contains copper and zinc.

(b) Stainless steel containing iron, carbon along with chromium and nickel.

(iii) Bronze is an alloy of copper and tin.

Brass does not get rusted easily whereas copper does. Stainless steel does not get rusted whereas iron does. Bronze is harder than copper and tin

Or

(i) Hydraulic washing: It is used for enrichment of oxides ore in which density ofimpurities is less than that of ore.

In this process, the crushed and finally powdered ore is washed with a steam of water.

The lighter impurities are washed away, leaving behind the heavier ore particles.

(ii) Froth floatation process: It is used to separate gangue from the sulphide oresespecially of copper. In this process, the finally powdered ore is mixed with water in a large tank to form a slurry. Then some pine oil is added to it. The sulphide ores are preferentially wetted by the pine oil whereas the gangue particles are wetted by water.

When air is blown through the mixture, the lighter oil froth carrying the metal sulphides rises to the top of the tank and floats as scum. It is then skimmed off and dried. The gangue particles being heavier, sink to the bottom of the tank.

(iii) Amalgam are alloys of mercury with other metals, e.g., Sodium amalgam, Zinc amalgam.

21.

(i) The pulmonary vein brings oxygenated blood to the human heart.

(ii) The left auricle of human heart receives oxygenated blood.

(iii) (a) When oxygenated blood comes into the left atrium it contracts and pours blood into left ventricle.

(b) The left ventricle contracts and the oxygenated blood from here is distributed to all parts of the body though aorta.

Or

(i) The pulmonary artery brings deoxygenated blood to the human heart.

(ii) The right auricle of human heart receives deoxygenated blood.

(iii) (a) Right auricle pours deoxygenated blood into right ventricle.

i From right ventricle deoxygenated blood flows to the lungs through pulmonary artery for oxygenation.

(d) (a) An instrument that measures electric current in a circuit is called Ammeter. The unit of electric current is Ampere (A). 1 ampere is constituted by the flow of 1 coulomb of charge through any point in an electric circuit in 1 second.

(b) (i) Variable resistance or rheostat (ii) Plug key or switch (closed)

(c)

(ii) Following graph was plotted between V and I values:

Or

(vi) Pure tungsten has a high resistivity and a high melting point (nearly 3000 o C). When an electric current is passed through the filament, the electric energy is converted to heat and light energy due to the heating of the filament to a very high temperature. Due to the high melting point of tungsten, the filament does not melt.

(vii) The resistivity of an alloy is generally higher than that of its constituent metals. Alloys do not oxidize (burn) readily at higher temperatures. Therefore conductors of electric heating devices such as toasters and electric irons are made of an alloy rather than pure metal.

(viii) The series arrangement is not used for domestic circuit because:

If connected in series total resistance will increase. Therefore current flowing through the circuit will be low.

If one appliance is switched off or gets damaged than all other appliances will also stop working because their electricity supply will be cut-off.

(iv) The resistance of a wire is inversely proportional to its cross-sectional area. Thus, a thick wire has less resistance and a thin wire has more resistance.

(v) Copper and aluminium wires are usually employed for electric energy transmission because copper and aluminium have very low resistivities.

23.

The production of electric current due to relative motion between a conductor and a magnetic field is called electromagnetic induction. Electric current produced due to this phenomenon is called induced current. This was discovered by Michael Faraday and Joseph Henry.

The direction of induced current can be reversed by reversing the direction of magnetic field. If the coil as well as the magnet are stationary, no current is induced in the coil.

There are two ways to producing induced current in the coil:

Self Induction: When the current flowing through a coil changes, then the current is inducedin the coil itself. This phenomenon is called Self induction.

Mutual Induction: Another way to induce current in a coil is by the process of mutualinduction. A current carrying coil called primary coil is placed close to a secondary coil as shown in figure.

When the current in primary coil is switched on, it takes a little time to rise from zero to a maximum value. This causes a momentary change in the magnetic field around this coil and hence induces a momentary current in the secondary coil. The same happens in reverse direction when the current in primary coil is switched off.

Or

To avoid risk of electric shock, the metal body of appliances is earthed. Earthing means to connect the metal case of the appliance to earth (i.e. zero potential) by mean of a metal wire called earth wire (in green insulation cover).

One end of the metal wire is buried in the earth. The appliances is connected to the earth by using he top pin of a 3-pin plug which connects to earth. Earthing saves us from electrical shocks.

31.

An electromagnet works on the principle of magnetic effect of current.

Aim: To construct an electromagnet.

Material required: Iron nail, copper wire, sand paper, cell, iron filings

Procedure:

(a) Take an iron nail and clean it with cloth.

(b) Take insulated copper wire of length 1 m and shave off both its end with the help of sand paper.

(c) Wind the wire nearly on the iron nail to form a cylindrical coil.

(d) Connect the free ends of the wire to the terminals of a cell.

(e) Bring iron filings near the nail and observe what happen.

Iron filings get attracted to the iron nail because iron nail behaves like a magnet when current passes through it.

Uses: Electromagnets are used in electric bell, cranes etc.

Or

Aim: To draw magnetic lines of force around a current carrying (a) straight conductor,

(b)circular loop

Material required: A cell, switch, connecting wires, an insulated copper wire, iron filings, cardboard.

Procedure:

Hang the cardboard horizontally on a stand.

Pass the copper wire through the centre of the cardboard.

Connect cell, switch and copper wire in series through the connecting wires.

Switch the circuit on sprinkle iron filings gently on the card board and tap it.

The iron filings will arrange themselves in the form of connecting rings around the wire.

Now bend the wire into a loop and pass it through the cardboard as shown. Repeat step

(iv) again.

Observe the pattern of field lines.

The magnetic field around a current carrying conductor appears in the form of concentric circles.

The magnetic field in the centre of a current carrying circular loop appears as straight lines.

25.

Option (c) is correct. Both CO

2

and SO

2 turns limewater milky.

CO

2

+ Ca(OH)

2

 CaCO

3

+ H

2

O

Carbon dioxide Limewater white ppt.

SO

2

+ Ca(OH)

2

 CaSO

3

+ H

2

O

Sulphur dioxide Limewater white ppt.

26. He should boil the leaf in Alcohol. Alcohol dissolved the chlorophyll and decolourise the leaf.

27.

R =

V



1.8 V

I 180 mA



1.8

 10 3 

1800

180 180

 10 

28.

(d)

29.

(a)

30.

(d)

31.

(b)

32.

(c)

33.

(b)

34.

(c)

35.

(c)

36.

(b)

Paper 2


SCIENCE (Theory)

Class – X


General Instructions: k) All questions are compulsory. l) The question paper comprises of two sections, A and B. You are to attempt both the sections. m) Questions 1 to 3 in section A are one mark questions. These are to be answered in one word or in one sentence. n) Questions 4 to 6 in section A are two marks questions. These are to be answered in about 30 words each. o) Questions 7 to 18 in section A are three marks questions. These are to be answered in about

50 words each. p) Questions 19 to 24 in section A are five marks questions. These are to be answered in about

70 words each. q) Questions 25 to 27 in section B are 2 marks questions and Questions 28 to 36 are multiple choice questions based on practical skills. Each question of multiple choice questions is a one mark question. You are to select one most appropriate response out of the four provided to you.

Section A

11.

What happens when Hydrogen combines with Oxygen in the presence of an electric current?

12.

Why is nutrition necessary for an organism?

13.

Why is tungsten metal selected for making filaments of incandescent lamp bulbs?

14.

Write two observations you would make when quicklime is added to water.

15.

16.

Where does cerebrospinal fluid occur in our body? Mention any two of its functions.

Draw a sketch of the iron fillings as you spray them on a magnet.

17.

(a) What is an ionic equation? Give an example.

(b) Write the name of following compounds:

(i) Mn(OH)

2

(ii) FeCl

3

7.

(a) What is Double displacement reaction? Give an example.

(b) Write balanced equation:

Sodium + Water  Sodium hydroxide + Hydrogen

8.

(i) What is the action on litmus of:

(a) Dry ammonia gas. (b) Solution of ammonia gas in water

(ii) State the observations you would make on adding ammonium hydroxide to aqueous solutions of (a) Ferrous sulphate, (b) Aluminium chloride.

2 What is an alloy? Name the constituents of 22-carat gold. Why is 24-carat gold converted to 22carat gold?

3 State reasons for the following:

(b) Aluminium oxide is called an amphoteric oxide.

(c) Sodium and potassium metals are kept immersed under kerosene oil.

(d) Hydrogen gas is not evolved when most metals react with nitric acid.

4 List two vital functions of the human kidney. Draw a labelled diagram of an artificial kidney.

5 Explain the process by which inhalation occurs during breathing in human beings.

6 Draw a diagram showing endocrine glands in a human male body. Label the following glands on it:

(a) Pituitary (b) Thyroid (c) Adrenal (d) Testes

17.

Name the unit used in selling electrical energy to consumers. Two lamps, one rated 100 W at

220 V and the other 40 W at 220 V are connected in parallel to a 220 V mains supply. Calculate the electric current drawn from the supply line.

18.

Draw the pattern of lines of force due to magnetic field associated with a current carrying straight conductor. State how the magnetic field produces changes:

(a) with an increase in current in the conductor and

(b) the distance from the conductor

19.

Vinod went to his ancestral village alongwith his father during the summer holidays. He found that the women of the village used dried cow-dug cakes (uple) as the fuel to cook food and for other heating purposes. One day Vinod went to Panchayat meeting in a village which is attended by all the village elders and requested them to install “Gobar Gas plant” in the village and used cow-dung in it to produce gobar gas, instead of burning cow-dung cakes directly. He explained the advantages of using the gobar gas as a fuel instead of cow-dung cakes. Everyone liked the idea and thanked Vinod for guidance.


(a) State one disadvantage of using dried cow-dung cakes as a fuel for cooking food.

(b) State one advantage of using gobar gas as a fuel for cooking food.

(c) What values are displayed by Vinod in this whole episode?


20.

(a) Write the principle of generation of electric power by a nuclear reactor. Name the coolant used in such a reactor.

Explain the process of generation of energy in the Sun and name the scientist who was first to propose it.

21.

Translate the following statements into chemical equations and then balance them:

Hydrogen gas combines with nitrogen to form ammonia.

Hydrogen sulphide gas burns in air to give water and sulohur dioxide.

Barium chloride reacts with aluminiumsulphate to give aluminium chloride and a precipitate of barium sulphate.

Potassium metal reacts with water to give potassium hydroxide and hydrogen gas.

Hydrogen sulphide gas reacts with oxygen gas to form solid sulphur and liquid water.

Or

Write the difference between Displacement reaction and Double displacement reactions. Write equations for these reactions also.

20.

Four metals A, B, C and D are, in turn, added to the following solutions one by one. The observations made are tabulated below:

Metal Iron (II) Sulphate Copper (II) Sulphate Zinc Sulphate Silver Nitrate

A No reaction

B

C

Displacement

No reaction

Displacement

---------

No reaction

---------

No reaction

No reaction

---------

---------

Displacement

D No reaction No reaction No reaction

Answer the following questions based on above information:

No reaction

19.

Which is the most active metal and why?

20.

What would be observed if B is added to a solution of Copper (II) sulphate and why?

21.

Arrange the metals A, B, C and D in order of increasing reactivity.

22.

Container of which metal can be used to store both Zinc sulphate and Silver nitrate solution?

23.

Which of the above solutions can be easily stored in a container made up of any of these metals?

Or

You are given the following materials:

(i) Iron nails

(iv) Copper powder

(ii) Copper sulphate solution

(v) Ferrous sulphate crystals

(iii) Barium chloride solution

(vi) quick lime

Identify the type of chemical reaction taking place when:

20.

Barium chloride solution is mixed with copper sulphate solution and a white precipitate is observed.

21.

On heating copper powder in air in a China dish, the surface of copper powder turns black.

22.

On heating green coloured ferrous sulphate crystals, reddish brown solid is left and smell of a gas having odour of burning sulphur is experienced.

23.

Iron nails when left dipped in blue copper sulphate solution become brownish in colour and the blue colour of copper sulphur fades away.

24.

Quick lime reacts vigorously with water releasing a large amount of heat.

21.

How is ‘Respiration’ is different from ‘Breathing’? Explain the process of ‘Aerobic respiration’ and ‘Anaerobic respiration’.

Or

Draw a diagram showing ‘Human respiratory system’. Label its following parts:

(i) Larynx (ii) Trachea (iii) Primary Bronchus (iv) Lungs Why do the walls of the trachea not collapse when there is less air in it?

21.

A household uses the following electric appliances:

(ii) Refrigerator of rating 400 W for 10 hours each day.

(jj) Two electric fans of rating 80 W each for 6 hours daily.

(kk) Six electric tubes of rating 18 W each for 6 hours daily.

Calculate the electricity bill for the household for the month of June if cost electrical energy is

` 3.00 per unit.

Or

(jj) The potential difference between two points in an electric circuit is 1 volt. What does is mean? Name a device that helps to measure the potential difference across a conductor.

(kk) Why does the connecting cord of an electric heater not glow while the heating element does?

(ll) Electric resistivities of some substances at 20 o C are given below:

Silver 1.60

 10

 8  m

Tungsten 5.2

 10

 8  m Iron

Copper 1.62  10

10.0

 10

 8  m

 8  m

Mercury 94.0  10

 8  m Nichrome

Answer the following questions using above data:

100  10

 6  m

(a) Among Silver and Coper, which one is a better conductor and why?

(b) Which material would you advise to be used in electrical heating devices and why?

22.

State Fleming’s Left hand rule. Write an activity to prove this rule.

24. What are magnetic field lines? How will you draw them? Write their characteristics.

Or

Show a domestic electric circuit with fuse, a bulb and a geyser from main electric line. Indicate also the capacity of fuse used for geyser and the bulb.

SECTION – B

25.

If we mix equal volume of 1 M NaOH solution with 1 M solution of HCl and then if we add blue litmus into it, then what will be the change in litmus paper? Write the chemical reaction involved.

26.

In an experiment on photosynthesis, a student fixed a strip of black paper on the dorsal surface of a Bougainvillea leaf in the morning. In the evening she tested the leaf for starch.

(a) What will be the result?

(b) Justify your answer

27.

In the experiment on studying the dependence of current (I) on the potential difference (V), three students plotted the following graphs between (V) and (I) as per their respective observations.

(a) Which observation is correct?

(b) Justify your answer.

28.

Four students I, II, III and IV were asked to examine the changes for blue and red litmus paper strips with dilute HCl (solution A) and dilute NaOH (solution B). The following observations were reported by the four students. The sign

  

indicating no colour change.

Litmus

Blue

Red

(I)

A

----

----

B

Red

Blue

Litmus

Blue

Red

(II)

A

Red

----

B

----

Blue

Litmus

Blue

Red

(III)

A B

Red Red

Blue Blue

Litmus

Blue

Red

(IV)

A B

Blue Blue

Red Red

The correct observation would be of the student:

(a) I (b) II (c) III (d) IV

(e) The apparatus should be kept air tight because:

(i) SO

2

is lighter than air.

(ii) SO

2

is soluble in water.

SO

2

will escape from the gaps. (iii)

(iv) SO

2

is poisonous.

(f) When acidified potassium dichromate solution is added to a jar containing sulphur dioxide gas, the solution becomes:

(a) colourless (b) brown (c) dark orange (d) green

(ix) Which structure out of I, II, III and IV marked in the given diagram of the epidermal peel of leaf should be labelled as stoma:


32. Phototropism : Shoots : Geotropism : __________

(a) Leaves (b) Flowers (c) Roots (d) Shoots

24.

The rest positions of the needles in a Milliammeter and Voltmeter were shown in figure A.

When a student used these in her experiment, the final readings of the needle were in the position shown in figure B.

The correct readings of the two instruments are:

(a) 34 mA and 4.2 V respectively (b) 37 mA and 4.8 V respectively

(c) 31 mA and 4.8 V respectively (d) 31 mA and 4.2 V respectively

25.

To study the dependence of current (I) on the potential difference (V) across a resistor, two students used the two set ups shown in figure (A) and (B) respectively. They kept the contact J in four different positions, marked (i), (ii), (iii), (iv) in the two figures.

For the two students, their Ammeter and Voltmeter readings will be minimum when the contact J is in the position:

(i) in both the set ups.

(iv) in both the set ups.

(iv) in set up (A) and (i) in set up (B)

(i) in set up (A) and (iv) in set up (B)

24.

A circular loop placed in a plane perpendicular to the place of paper carries a current when the key is ON. The current as seen from points A and B (in the plane of paper and on the axis of the coil) is anti-clockwise respectively. The magnetic field lines from B to A. The N-pole of the resultant magnet is on the face close to:

(a) A

(b) B

(c) A, if the current is small and B, if the current is large.

(d) B, if the current is small and A, if the current is large.

36.

In a hydro power plant:

(a) Potential energy possessed by stored water is converted into electricity.

(b) Kinetic energy possessed by stored water is converted into potential energy.

(c) Electricity is extracted from water.

(d) Water is converted into steam to produce electricity.


SCIENCE (Theory)

Class – X

(Solutions)

SECTION-A

6.

r) When Hydrogen combines with Oxygen in the presence of electric current, water is formed.

2H

2

+ O

2

 electric  2H

2

O current

18.

Nutrition is necessary for an organism because it serves as energy source which is utilized in all physiological activities like growth, development and maintenance of life.

19.

Tungsten metal has high resistivity and high melting point.

20.

(i) The solution becomes hot.

(ii) Quicklime forms milky solution with water.

CaO + H

2

O  Ca(OH)

2

8.

The cerebrospinal fluid occurs in the sub-arachnoid space in the cerebral ventricles and spinal canal.

Functions:

9.

It serves to maintain a constant pressure inside the cranium.

10.

It provides protection to the ears against mechanical injury and shock.

(iii) a) The equation involving ions and elements is called an ionic equation, e.g.,

2I

  aq

  Br

2

 aq

  I

2

 aq

  2Br

  aq



(b) (i) Manganese Hydroxide, (ii) Ferric chloride

7 Double displacement reaction is a reaction in which compounds exchange their ions, i.e. two atoms or ions displace each other, e.g.,

Ba



NO

3



2

 aq







NH

4



2

CO

3

 aq



 BaCO

3

 s



 2NH

4

NO

3

 aq



Barium Nitrate Ammonium carbonate Barium Ammonium Nitrate Carbonate

(b) 2Na + 2H

2

O  2NaOH + H

2

9.

(i) (a) Litmus has no action on dry ammonia gas.

(b) Solution of ammonia gas in water turns red litmus blue.

13.

(a) When ammonium hydroxide is added to ferrous sulphate solution, geren precipitate is formed.

FeSO

4

+ 2NH

4

OH  Fe(OH)

2

+ (NH

4

)

2

SO

4

(b) Gelatinous white precipitate is formed.

AlCl

3

+ 3NH

4

OH  Al(OH)

3

+ 3NH

4

Cl

10. An Alloy is homogeneous mixture of two or more metals. Ore of them can be non-metals also.

22-carat gold contains

22

24

 100  90.66% gold and remaining copper.

It is because 24-carat gold (pure gold) is too soft to make ornaments.

11.

(a) It reacts with both acids as well as bases therefore, it is called amphoteric oxide.

(b) It is because they are highly reactive and catch fire in moist air.

(c) It is because nitric acid is strong oxidizing agent

12.

The vital functions of human kidney are as follows:

Excretion: Metabolic wastes are excreted in the form of urine.

(ii) Osmoregulation: Maintenance of water quantity in all the parts of the body.

13.

Inhalation or inspiration is the process by which air is brought into the lungs during breathing in human beings. It involves the following steps.

(i) The external intercostal muscles contract causing ribs to pull out and chest cavity to expand.

(ii) Diaphragm contracts and is brought down a little. This also expands the chest cavity.

(iii) There is a contraction of the abdominal muscles. The expansion of chest cavity creates a partial vacuum and atmospheric air rushes the lung.

14.

15. In parallel connection,

⇒

1



1



1

R p

R

1

R

2

P = 100 + 40 = 140 W

Potential applied = 220 V

⇒

V 2



V 2



V 2

R p

R

1

R

2

⇒ P = P

1

+ P

2

 Current drawn from the power supply I = P  140  7 A

V 220 11

16.

(i) Magnitude of field increases as



B  I



(ii)

Magnetic field decreases with an increase in distance from the conductor

B 

1 r

17.

(a) Burning of dried cow-dung cakes as fuel produces a lot of smoke which cause air pollution in the houses and damage the health of all the family members, especially women and children.

(b) Gobar gas burns without producing any smoke and hence does not cause any air pollution.

This ensures good health for village people especially women and children who spend most of their time inside the house.

(c) General awareness of the alternative sources of energy and concern about the environment and health of village people.

18.

(a) It is based on the fission of self sustaining controlled chain reaction of U-235. The heat produced in the reactor is taken away the coolant such as water or heavy water or liquid sodium and used to heat the water and convert it into steam. The high pressure steam rotates the turbine which generates electricity.

(b) The process of generation of energy in the sun is nuclear fusion. For every fusion of deuterium, it releases 21.6 MeV energy. It was Hans Bethe who first proposed it. Helium is the product of the fusion.

1

2 H +

1

2 H  4

2

He + 21.6 MeV

19.

(a) N

2

 g



+ 3H

2

 g

  2NH

3

 g



(b) 2H

2

S

 g



+ 3O

2

 g

  2H

2

O

 l



+ 2SO

2

 g



(c) 3BaCl

2

 aq



+ Al

2



SO

4



3

 aq



 2AlCl

3

 aq



 3BaSO

4

 s





(d) 2K

 s

  2H

2

O

 l

  2KOH

 aq

  H

2

 g



(e) 2H

2

S

 g



+ O

2

 g



 2S

 s



+ 2H

2

O

 l



Or

Displacement reaction: In a displacement reaction, a more reactive element displaces orremoves another element from its compound.

For example, Zinc being more reactive, displaces copper from its compound.

Zn

 s

  CuSO

4

 aq

  ZnSO

4

 aq

  Cu

 s



Double Displacement reaction: In case double displacement reaction, two compounds reactby exchanging their ions and form two new compounds.

For example, Silver and Sodium exchange their ions, NO

3

 and Cl

 respectively and form two

20. (i) ‘B’ is most active metal because it can displace iron from iron (II) sulphate, whereas A, C, D new compounds in the following reaction.

AgNO

3

 aq cannot displace iron from iron (II) sulphate.

3

(c) ‘B’ will displace copper (reddish brown) from copper sulphate solution because ‘B’ can displace both iron as well as copper.

(d) B > A > C > D

D, C, A, B is increasing order of reactivity.

(f) Zinc sulphate



 NaCl

 aq



 AgCl

 s



 NaNO

 aq



(e) Zinc sulphate solution can be stored in metal B, C and D, silver nitrate solution can be stord in container of metal D.

Or

(a) BaCl

2

(aq) + CuSO

4

(aq)  BaSO

4

(s) + CuCl

2

(aq)

Barium Copper

Chloride sulphate

White ppt

(Barium sulphate)

Copper chloride

It is precipitation reaction and Double Displacement reaction.

(b) 2Cu (s) + O

2

(g)  2CuO (s)

Copper Oxygen Black copper oxide

It is Combination reaction. It can also be called as Oxidation reaction.

heat

(c) 2FeSO

4

(s)  Fe

2

O

3

(s) + SO

2

Iron (II) sulphate (Ferric oxide) Sulphur

+ SO

3

(g)

Sulphur

Green Reddish Brown dioxide

Solid

It is Decomposition reaction.

trioxide

(smell of burning sulphur)

(d) Fe (s) + CuSO

4

(aq)  FeSO

4

(aq) + Cu(s)

Iron Blue Pale green Copper (reddish brown)

It is Single Displacement reaction. Iron can displace copper from copper sulphate solution. 21. Difference between Breathing and Respiration:

Breathing Respiration

(i) It is a bio-physical process where oxygen (i) It is a bio-chemical process where is taken and carbon dioxide is given out.

oxidation of food occurs and carbon

(ii) It does not require enzymes.

dioxide is released.

(ii) It occurs in the presence of respiratory enzymes.

(iii) No energy is released during the process.

(iii) Energy is released in the form of ATP.

(iv) It occurs at organ level.

(v) It is found in higher animals only.

(iv) It occurs at cellular level.

(v) It is found in all animals and plants.

Aerobic respiration: When tissues carry our oxidation of food materials, utilizing molecularoxygen, the process is called Aerobic respiration.

Glycolysis

Glucose  Pyruvic acid  6CO

(in cytoplasm)

 in presence of O 2





in mitochondria



(2 molecules of pyruvate)

2

+ 6H

2

O + 38 ATP

(energy)

Anaerobic respiration: When cells or organisms carry out oxidation of nutrients withoututilizing molecular oxygen, the process is called Anaerobic respiration.

Glucose 

Glycolysis

Pyruvic acid  2C

(in cytoplasm)

 in absence of O 2





yeast fermentation



(2 molecules of pyruvate)

2

H

5

OH + 2CO

2

+ 2 ATP

(energy)

Or

The walls of trachea does not collapse when there is less air in it as it is supported by rings of cartilage.

22. Energy consumed per day by refrigerator = 0.4 kW x 10 h = 4 kWh

(Power of refrigerator = 400 W =

400

kW = 0.4 kW)

1000

Energy consumed per day by fans = 2 x 0.08 kW x 6 h = 0.96 kWh

80

(Power of each fan = 80 W = kW = 0.08 kW)

1000

Energy consumed per day by Lights = 6 x 0.018 kW x 6 h = 0.648 kWh

Total energy consumed per day = 4 + 0.96 + 0.648 = 5.608 kWh

Energy consumed in 30 days = 30 x 5.608 = 168.24 kWh

Cost of 261.84 units @ ` 3.00 = 1.68.24 x 3 = ` 504.72

Or

23.

The potential difference between two points is 1 volt means that if a charge of 1 coulomb is moved from one point to other, 1 joule of work is required.

The potential difference across a conductor us measured by means of an instrument called the “Voltmeter”.

(c) The electric power P is given by P = I 2 R

The resistance of the heating element is very high. Large amount of heat generates in the heating element and it glows hot.

The resistance of connecting cord is very low. Thus, negligible heat generates in the connecting cord and it does not glow.

(d) (a) Silver is a better conductor due to its lower resistivity.

(b) Nichrome should be used in electrical heating devices due to very high resistivity.

28.

Fleming’s Left hand rule: Stretch the first three fingers of the left hand mutuallyperpendicular to each other such that the fore finger points the direction of magnetic field, the middle finger points the direction of current, then the thumb will indicate the direction of force experienced by the conductor. It is to be applied when the current and field are perpendicular to each other.

24.

Magnetic field: Surrounding a magnet its influence is felt by any other magnetic element.

Itmay be an attractive of a repulsive influence.

The direction of magnetic field at a point is determined by drawing a tangent at that point. The direction of tangent gives the direction of magnetic field.

Characteristics of Magnetic field lines:

(i) The direction of the magnetic field is indicated by the arrow in the line at any point

(Tangent).

(ii) The field lines come out of the North pole and get into the South pole (closed loops are formed).

(iii) The strength of magnetic field is indicated by the closeness of the field lines. Closer the lines, more will be the strength and farther the lines, lesser will be the field strength.

(iv) No two field lines will intersect each other – if they intersect there will be two different directions for field at the same point which is not possible.

Or

25.

No effect will be on blue. NaOH

+ HCl  NaCl + H

2

O

NaCl is neutral, so blue litmus will remain blue. There is no effect.

26.

(a) The entire leaf turned blue black.

(b) In the diffused light reaching the ventral surface, photosynthesis takes place and so the whole leaf responds to starch test.

27.

(a) The observation of student II is correct.

(b)

28.

(b)

As V = 0, then I should also be zero, since V = IR.

29.

(c)

30.

(d)

31.

(c)

32.

(c)

33.

(c)

34.

(b)

35.

(a)

36.

(a)

Paper 3


SCIENCE (Theory)

Class – X

Time allowed: 3 hours

General Instructions:

Maximum Marks: 90 s) All questions are compulsory. t) The question paper comprises of two sections, A and B. You are to attempt both the sections. u) Questions 1 to 3 in section A are one mark questions. These are to be answered in one word or in one sentence. v) Questions 4 to 6 in section A are two marks questions. These are to be answered in about 30 words each. w) Questions 7 to 18 in section A are three marks questions. These are to be answered in about

50 words each. x) Questions 19 to 24 in section A are five marks questions. These are to be answered in about

70 words each. y) Questions 25 to 27 in section B are 2 marks questions and Questions 28 to 36 are multiple choice questions based on practical skills. Each question of multiple choice questions is a one mark question. You are to select one most appropriate response out of the four provided to you.

Section A

21.

Why does milk become sour if kept fora long time?

22.

Name the respiratory organs of: (i) fish, (ii) mosquito, (iii) earthworm.

23.

Name a metal which offers higher resistance to the passage of electricity other than copper.

24.

(i) An aqueous solution has a pH value of 7.0. Is this solution acidic, basic or neutral?

(a) Which has a higher pH value, 1 M HCl or 1 M NaOH solution?

25.

Taking the example of auxins and cytokinins together, explain (i) a synergistic action in plants,

(a) an antagonistic action in plants.

26.

A wire carrying current is passing through a hole at the middle of a cardboard. Plot the magnetic field lines.

27.

What information can be included in a chemical reaction? (Any 3 points)

28.

What happens when Zn metal is dipped in CuSO

4

solution? Give the chemical reaction involved.

State which is more reactive, Zn or Cu?

29.

(a) Name the raw material used in the manufacture of sodium carbonate by Solvay process.

(b) How is the sodium hydrogen carbonate formed during Solvay process separated from a mixture of NH

4

Cl and NaHCO

3

?

(c) How is sodium carbonate obtained from sodium hydrogen carbonate?

12.

(a) Explain the term ‘roasting’ as used in metallurgical processes. Give one suitable example for it.

(a) What changes takes place when Cinnabar (HgS) is heated in air for a long enough time?


(b) Metals are good conductors of heat.

(c) Addition of some silver to pure gold for making ornaments.

(d) Inability of non-metals for displacing hydrogen from dilute sulphuric acid.

9 Name the three kinds of cells present in blood. Write one function each of them.

10 Draw a diagram of human alimentary canal showing duodenum, small intestine, liver and pancreas.

11 Draw a diagram of human brain and label the following parts:

(a) Cerebrum (b) Hypothalamus (c) Medulla oblongata (d) Cerebellum

20.

Vikalp’s father had constructed a new room in their house. An electrician was called in to do the electric wiring. The electrician was asked to do wiring for two fans, two bulbs, a light socket and a power socket. Vikalp studies in tenth standard. Just when the electrician had completed the wiring, Vikalp returned home from school. Vikalp wanted to check the wiring by using all the switches and sockets. Vikalp found that the two fans and two sockets worked properly, each having a separate switch but there was a problem in the working of bulbs. Both the bulbs could be switched on and switched off with the same switch. Vikalp explained the mistake in wiring to electrician and then two separate switches were provided for the two bulbs.


(a) In what way were the two fans and two sockets connected in the household circuit by electrician?

(b) What mistake made by the electrician in connecting two bulbs in the circuit?

(c) What values were displayed by Vikalp during this incident?


22.

Draw the pattern of field lines due to a bar magnet. Mention any two properties of the magnetic field lines.

23.

(a) Name the device used to convert:

Solar energy into heat and

Solar energy into electricity.

Explain the principle of working of a wind mill.

24.

Name three forms in which energy from ocean is made available for use. What are OTEC power plants? How do they operate?

25.

Write the balanced chemical equations for the following reactions:

Calcium hydroxide + Carbon dioxide  Calcium carbonate + Water

(ii) Zinc + Silver nitrate  Zinc nitrate + Silver

(iii) Aluminium + Chromium oxide  Aluminium oxide + Chromium

(iv) Barium chloride + Potassium sulphate  Barium sulphate + Potassium chloride

(v) Hydrogen + Chlorine  Hydrogen chloride

Or

Give the characteristic tests for the following gases:

(i) CO

2

(ii) SO

2

(iii) O

2

(iv) H

2

20. Differentiate between an alloy and an amalgam. How are alloys made? State with examples any two properties in which an alloy may be different from those of its constituents. Write the constituents and special advantages of:

(i) Stainless Steel (ii) Magnalium

Or

What is meant by the term “Enrichment of Ore”? Name four methods generally used for enrichment of ore. With the help of a labelled diagram, describe the method for the enrichment of sulphide ore.

21. Define the terms ‘Nutrition’ and ‘Nutrients’. List two differences between ‘Holozoic nutrition’ and ‘Saprophytic nutrition’. Give two examples of each of these two types of nutrition.

Or

Explain why the rate of photosynthesis in plant is low both of lower and higher temperature.

Is green light most or least useful in photosynthesis and why?

Describe an activity to show that chlorophyll is necessary for photosynthesis in plants.

22.

Draw the schematic diagram of a circuit containing the following electrical equipments:

(i) a resistance (ii) a voltmeter (iii) an electric bulb

(iv) a cell (v) plug key (open) (vi) an ammeter

Or

Three incandescent bulbs of 100 W each are connected in series in an electric circuit. In other set of three bulbs of the same wattage are connected in parallel to the source.

(b) Will the bulb in the two circuits glow with the same brightness? Justify your answer.

(c) Now, let one bulb in both the circuits get fused. Will the rest of the bulbs continue to glow in each circuit? Give reason.

(iii)

State ‘Fleming’s Right hand rule’. Give an activity to show this rule.

24.

Draw the line of forces (indicating field direction) of the magnetic field through and around (a) a single loop wire carrying electric current and (b) a solenoid carrying electric current.

Or

2 Draw a schematic diagram of a domestic electric circuit which includes a main fuse, a power meter, a light point, a fan and a power plug.

3 Why is it necessary to earth the metallic electric appliances?

Section B

25.

When red litmus paper is added to limewater, then what will be the change in litmus paper?

Give reason. Write the chemical formula of limewater also.

26.

A destarched leaf on a potted plant was covered with black (A), white (B) and transparent (C) strips of paper as shown in the figure.

After six hours to exposure to sunlight the leaf was removed from the plant and tested for starch.

(v) What changes will be observed?

(vi) Justify your answer.

27A student draw the following circuit diagram for the experiment on studying the dependence of current (I) on potential difference (V) across a resistor. What are the parts labelled X, Y and Z in this diagram respectively? Justify your answer also.

28. When the colour of pH paper becomes red, the solution is _________ and pH is between _________.

(a) strongly acid, pH = 1 to 2 (b) weakly acid, pH = 6 to 7

(c) strongly basic, pH = 12 to 13 (d) weakly basic, pH = 7 to 8

29.

To study the reaction between HCl and Zn student has to :

(a) Heat the mixture

(b) Add HCl on hot Zn granules

(c) Add ho t HCl to Zn granules

(d) Simply add dil. HCl to Zn granules at room temperate

30.

If iron are added to ZnSO4 solution possible observation would be.

(a) No reation takes place

(b) Silvery cotting on iron nails

(c) Black cotting on iron nails

(d) Pale green colour of solution is seen

31.

Growth hormone : Pituitary : Thyroxin : __________

(a) Thyroid (b) Parathyroid (c) Pancreas (d) Adernal

32. How many spinal nerves are present in human being:

(a) 31 pairs (b) 19 pairs (c) 27 pairs (d) 30 pairs

33 The rest positions of the needles in a Milliammeter and Voltmeter when not being used in a circuit are as shown in the figure. The ‘zero error’ and ‘least count’ of these two instruments are:

(+4 mA, –0.2 V) and (1 mA, 0.1 V) respectively


(–4 mA, +0.2 V) and (2 mA, 0.2 V) respectively


34 While performing the experiment on studying the dependence of current (I) on the potential difference (V) across a resistor, four students I, II, III and IV set up the circuit is shown.

The correct result will be obtained by the student.


35 If the key in the arrangement is taken out (the circuit is made open) and magnetic field lines are drawn over the horizontal plane, the lines are: a.

concentric circles. b.

elliptical in shape. c.

straight lines parallel to each other. d.

concentric circles near the point O but of elliptical shapes as we go away from it.

36 Fuel used in thermal power plants is:

(a) water (b) uranium (c) biomass (d) fossil fuels


SCIENCE (Theory)

Class – X

Time allowed: 3 hours


Maximum Marks: 90 z) All questions are compulsory. aa) The question paper comprises of two sections, A and B. You are to attempt both the sections. bb) Questions 1 to 3 in section A are one mark questions. These are to be answered in one word or in one sentence. cc) Questions 4 to 6 in section A are two marks questions. These are to be answered in about 30 words each. dd) Questions 7 to 18 in section A are three marks questions. These are to be answered in about

50 words each. ee) Questions 19 to 24 in section A are five marks questions. These are to be answered in about

70 words each. ff) Questions 25 to 27 in section B are 2 marks questions and Questions 28 to 36 are multiple choice questions based on practical skills. Each question of multiple choice questions is a one mark question. You are to select one most appropriate response out of the four provided to you.

Section A

30.

Why does milk become sour if kept for a long time?

31.

Name the respiratory organs of: (i) fish, (ii) mosquito, (iii) earthworm.

32.

Name a metal which offers higher resistance to the passage of electricity other than copper.

33.

(i) An aqueous solution has a pH value of 7.0. Is this solution acidic, basic or neutral?

(a) Which has a higher pH value, 1 M HCl or 1 M NaOH solution?

34.

Taking the example of auxins and cytokinins together, explain (i) a synergistic action in plants,

(a) an antagonistic action in plants.

35.

A wire carrying current is passing through a hole at the middle of a cardboard. Plot the magnetic field lines.

36.

What information can be included in a chemical reaction?

37.

What happens when Zn metal is dipped in CuSO

4

solution? Give the chemical reaction involved.

State which is more reactive, Zn or Cu?

38.

(a) Name the raw material used in the manufacture of sodium carbonate by Solvay process.

(d) How is the sodium hydrogen carbonate formed during Solvay process separated from a mixture of NH

4

Cl and NaHCO

3

?

(e) How is sodium carbonate obtained from sodium hydrogen carbonate?

13.

(a) Explain the term ‘roasting’ as used in metallurgical processes. Give one suitable example for it.

(a) What changes takes place when Cinnabar (HgS) is heated in air for a long enough time?


(b) Metals are good conductors of heat.

(c) Addition of some silver to pure gold for making ornaments.

(d) Inability of non-metals for displacing hydrogen from dilute sulphuric acid.

13 Name the three kinds of cells present in blood. Write one function each of them.

14 Draw a diagram of human alimentary canal showing duodenum, small intestine, liver and pancreas.

15 Draw a diagram of human brain and label the following parts:

(a) Cerebrum (b) Meninges (c) Medulla oblongata (d) Cerebellum

21.

Vikalp’s father had constructed a new room in their house. An electrician was called in to do the electric wiring. The electrician was asked to do wiring for two fans, two bulbs, a light socket and a power socket. Vikalp studies in tenth standard. Just when the electrician had completed the wiring, Vikalp returned home from school. Vikalp wanted to check the wiring by using all the switches and sockets. Vikalp found that the two fans and two sockets worked properly, each having a separate switch but there was a problem in the working of bulbs. Both the bulbs could be switched on and switched off with the same switch. Vikalp explained the mistake in wiring to electrician and then two separate switches were provided for the two bulbs.


(a) In what way were the two fans and two sockets connected in the household circuit by electrician?

(b) What mistake made by the electrician in connecting two bulbs in the circuit?

(c) What values were displayed by Vikalp during this incident?


26.

Draw the pattern of field lines de to a bar magnet. Mention any two properties of the magnetic field lines.

27.

(a) Name the device used to convert:

Solar energy into heat and

Solar energy into electricity.

Explain the principle of working of a wind mill.

28.

Name three forms in which energy from ocean is made available for use. What are OTEC power plants? How do they operate?

29.

Write the balanced chemical equations for the following reactions:

Calcium hydroxide + Carbon dioxide  Calcium carbonate + Water

(vi) Zinc + Silver nitrate  Zinc nitrate + Silver

(vii) Aluminium + Chromium oxide  Aluminium oxide + Chromium

(viii) Barium chloride + Potassium sulphate  Barium sulphate + Potassium chloride

(ix) Hydrogen + Chlorine  Hydrogen chloride

Or

Give the characteristic tests for the following gases:

(i) CO

2

(ii) SO

2

(iii) O

2

(iv) H

2

20. Differentiate between an alloy and an amalgam. How are alloys made? State with examples any two properties in which an alloy may be different from those of its constituents. Write the constituents and special advantages of:

(i) Stainless Steel (ii) Magnalium

Or

What is meant by the term “Enrichment of Ore”? Name four methods generally used for enrichment of ore. With the help of a labelled diagram, describe the method for the enrichment of sulphide ore.

21. Define the terms ‘Nutrition’ and ‘Nutrients’. List two differences between ‘Holozoic nutrition’ and ‘Saprophytic nutrition’. Give two examples of each of these two types of nutrition.

Or

Explain why the rate of photosynthesis in plant is low both of lower and higher temperature.

Is green light most or least useful in photosynthesis and why?

Describe an activity to show that chlorophyll is necessary for photosynthesis in plants.

23.

Draw the schematic diagram of a circuit containing the following electrical equipments:


(iv) a cell (v) plug key (open) (vi) an ammeter

Or

Three incandescent bulbs of 100 W each are connected in series in an electric circuit. In other set of three bulbs of the same wattage are connected in parallel to the source.

(d) Will the bulb in the two circuits glow with the same brightness? Justify your answer.

(e) Now, let one bulb in both the circuits get fused. Will the rest of the bulbs continue to glow in each circuit? Give reason.

(iv) State ‘Fleming’s Right hand rule’. With a labelled diagram, describe the working of an A.C. electric generator.

Or

Explain with neat and labelled diagram, the principle, construction and working of D.C. generator, showing the output.

25.

Draw the line of forces (indicating field direction) of the magnetic field through and around (a) a single loop wire carrying electric current and (b) a solenoid carrying electric current.

Or

4 Draw a schematic diagram of a domestic electric circuit which includes a main fuse, a power meter, a light point, a fan and a power plug.

5 Why is it necessary to earth the metallic electric appliances?

Section B

27.

When red litmus paper is added to limewater, then what will be the change in litmus paper?

Give reason. Write the chemical formula of limewater also.

28.

A destarched leaf on a potted plant was covered with black (A), white (B) and transparent (C) strips of paper as shown in the figure.

After six hours to exposure to sunlight the leaf was removed from the plant and tested for starch.

(vii) What changes will be observed?

(viii) Justify your answer.

37.

A student draw the following circuit diagram for the experiment on studying the dependence of current (I) on potential difference (V) across a resistor. What are the parts labelled X, Y and

Z in this diagram respectively? Justify your answer also.

28. When the colour of pH paper becomes red, the solution is _________ and pH is between _________.

(a) strongly acid, pH = 1 to 2 (b) weakly acid, pH = 6 to 7

(c) strongly basic, pH = 12 to 13 (d) weakly basic, pH = 7 to 8

32.

When SO

2

gas is passed through acidified K

2

Cr

2

O

7

solution:

(a) The solution becomes green due to formation of K

2

SO

4

.

(b) The solution becomes green due to formation of Cr

(a) It is poisonous.

2

(SO

4

)

(c) The solution becomes yellow due to formation of K

2

SO

4

.

(d) The solution becomes red due to formation of Cr

33.

SO

2

gas should not be inhaled because:

2

(SO

4

)

2

.

2

.

(b) It is acidic in nature.

(c) It is lighter than air.

(d) It is pungent smelling.

34.

Growth hormone : Pituitary : Thyroxin : __________

(a) Thyroid (b) Parathyroid (c) Pancreas (d) Adernal

32. How many spinal nerves are present in human being:

(a) 31 pairs (b) 19 pairs (c) 27 pairs (d) 30 pairs

26.

The rest positions of the needles in a Milliammeter and Voltmeter when not being used in a circuit are as shown in the figure. The ‘zero error’ and ‘least count’ of these two instruments are:





25.

While performing the experiment on studying the dependence of current (I) on the potential difference (V) across a resistor, four students I, II, III and IV set up the circuit is shown.

The correct result will be obtained by the student.


2 If the key in the arrangement is taken out (the circuit is made open) and magnetic field lines are drawn over the horizontal plane, the lines are:

(a) concentric circles.

(b) elliptical in shape.

(c) straight lines parallel to each other.

(d) concentric circles near the point O but of elliptical shapes as we go away from it.

3 Fuel used in thermal power plants is:

(a) water (b) uranium (c) biomass (d) fossil fuels

Paper 4


SCIENCE (Theory)

Class – X


General Instructions: gg) All questions are compulsory. hh) The question paper comprises of two sections, A and B. You are to attempt both the sections. ii) Questions 1 to 3 in section A are one mark questions. These are to be answered in one word or in one sentence. jj) Questions 4 to 6 in section A are two marks questions. These are to be answered in about 30 words each. kk) Questions 7 to 18 in section A are three marks questions. These are to be answered in about

50 words each. ll) Questions 19 to 24 in section A are five marks questions. These are to be answered in about

70 words each. mm) Questions 25 to 27 in section B are 2 marks questions and Questions 28 to 36 are multiple choice questions based on practical skills. Each question of multiple choice questions is a one mark question. You are to select one most appropriate response out of the four provided to you.

Section A

39.

What is the chemical formula of bleaching powder ?

40.

Name the excretory unit of kidney.

41.

There are two electric bulbs (i) marked 60 W, 220 V and (ii) marked 100 W, 220 V. Which one of the two has a higher resistance?

42.

What is efforescence? Give an example.

43.

Differentiate between tropic and nastic movements in plants, give one example of each..

44.

What are magnetic lines of force? Roughly trace the magnetic field lines for a bar magnet.

45.

What are the displacement reactions. Give example also.

46.

What is a chemical formula? What information is conveyed by a chemical formula.

47.

What is observed when:

(a) Dilute sulphuric acid is added to solid sodium carbonate.

(b) Hot concentrated sulphuric acid is added to sulphur.

(c) Sulphur dioxide is passed through lime water?

Also write chemical equations to represent the chemical reaction taking place in each case. 10. Explain the following terms by giving one example of each:

(i) Mineral (ii) Ore (iii) Gangue

2 Give reasons:

(b) Metals are regarded as electropositive elements.

(c) When a piece of Copper metal is added to a solution of Zinc sulphate, no change takes place, but the blue colour of Copper sulphate fades away when a piece of Zinc is placed in its solution.

(d) Articles made of aluminium do not corrode even though aluminium is an active metal.

3 Draw a diagram of the human respiratory system and label the following in it:

(a) Lungs (b) Primary bronchus (c) Trachea (d) Larynx

14.

Give reasons for the following:

(a) The glottis is guarded by epiglottis.

(b) The lung alveoli are covered with blood capillaries.

(c) The wall of trachea is supported by cartilage rings

15.

What are the male and female gonads in human beings? State any two functions of each of them.

16.

(a) Draw a schematic diagram of a circuit consisting of a battery of five 2 V cells, a 5 ohm resistor and a plug key, all are connected in series

(b) Calculate the electric current passing through the above circuit when the key is closed.

22.

How does the strength of the magnetic field at the centre of a circular coil of wire depend upon:

(a) the radius of the coil the number of turns of wire in the coil the strength of current flowing in the coil?

18.

(a) Name the four gases commonly present in biogas.

(b) list two advantages of using biogas over fossil fuels.

19.

Dinesh is a student of class 10 th standard. He went to a remote area of Rajasthan for trekking with his friends. Dinesh found that it was a sparsely inhabited area. He was surprised to know that there was still no electricity in this area. The people used kerosene oil lamps to light up their homes at night and there were no street lights. The children also had to study with kerosene lamps at night. The village farmers used diesel to run irrigation pumps. Actually there were no pwer transmission lines which could bring electricity to this remote area.

Dinesh was really disturbed by the living conditions of the people in thei part of Rajasthan. One day Dinesh gathered all the people of village in the village school. He told them thay if they put pressure on their area MLAs and MPs for making available the required funds, then he could tell them about the devices to light up their homes and streets at night, play radio and television and also run irrigation pumps with electricity without there being power

transmission lines. All the people agreed and Dinesh described them the devices to get electricity in their area in detail. The village people were very happy to know this and soon they got electricity in their area.

Read the passage and answer the following questions:

24.

What was the device described by Dinesh to the village people to obtain electricity locally?

25.

What source of energy is made uses of in this device to obtain electricity?

26.

Why do you think this device is more appropriate for an area like Rajasthan?

27.

What is the name of the single unit of this device?

28.

What values are shown by Dinesh in this incident?


25.

You are provided with two containers made up of copper and aluminium. You are also provided with solutions of dil. HCl, dil. HNO

3

, ZnCl

2

and H

2

O. In which of the above containers these solutions can be kept?

Or

What happens when zinc granules are treated with dilute solution of H

2

SO

4

, HCL, HNO

3

, NaCl and NaOH? Also write the chemical equations if reaction occurs.

20. (a) What is an ‘activity series’ of metals? Arrange the metals Zn, Mg, Al, Cu and Fe in a decreasing order of reactivity.

22.

What would you observe when you put: some zinc pieces into blue copper sulphate solution? some copper pieces into green ferrous sulphate solution?

23.

Name a metal which combines with hydrogen gas. Name the compound formed.

Or

Describe with examples the following steps associated with the extraction of metals from their ores:

(c) Froth-floatation process

(d) Roasting of an ore

(f) Calcinations of an ore

(v) Explain the process of Photosynthesis in plants. List four factors which influence this process and describe how each of them affects the rate of the photosynthesis process.

Or

List three differences between respiration in plants and respiration in animals. Describe with a labelled diagram how gaseous exchange occurs through root hair in plants.

26.

(i) State and prove the Joule’s law of heating.

Give the commercial unit of electrical energy and relate it to Joule.

When 40 W, 220 V bulbs are connected in series to a source of 220 V, find the current flowing in each. If one of the bulb fuses, what will be the current drawn from the source of

220 V?

Or

(iv) Give reason, explain how he resistivity of the conductor vary if: area is halved? length is doubled? area is doubled? both area and length are doubles?

(v) Draw the schematic diagram of a circuit containing the following electrical components:


(iv) a cell (v) lug key (open) (vi) an ammeter

29.

Calculate the electricity bill amount for a month of 30 days, if the following devices are used as specified:

4 bulbs of 60 W for 6 hours.

3 tubelights of 40 W for 8 hours.

A refrigerator of 300 W for 24 hours.

An electric mixer of 750 W for 1 hour.

A TV of 100 W for 6 hours.

The cost per unit of electricity consumed is Rs.2.50 for first 50 units and Rs.3.00 for every unit consumed in excess of 50.

Or

A 60 W bulb is connected (i) in series and (ii) in parallel with a room heater and is further connected across the mains. If 60 W bulb is now replaced by 100 W bulb in each case, will the heat produced by heater be less or more? Give reason.

24. (a) What are Magnetic field lines? How is the direction of a magnetic field at a point determined?

(b) Draw two field lines around a bar magnet along its length on its two sides and mark the field directions on them by arrow marks.

(c) List any three properties of magnetic field lines.

Or

Why is pure iron not used for making permanent magnets? Name one materials used for making permanent magnets.

Describe how permanent magnets are made electrically.

State two examples of electrical instruments made by using permanent magnets.

Section B

(x) If phenolphthalein is added to dilute HCl, then what will happen? Justify your answer also.

(xi) (a) Why does plant cool the atmosphere?

Define that term also.

(xii) The given wire made of material resistivity '  ' is stretched to triple its length. Then what will be new resistivity? Justify your answer also.

(xiii) Conc. H

2

SO

4

should be kept away from body because:

(a) it is oily liquid.

(b) it reacts with skin which gets burnt.

(c) of its pungent smell.

(d) it has high boiling point.

35.

: To study the reaction between HCl and Zn student has to :

(a) Heat the mixture

(b) Add HCl on hot Zn granules

(c) Add ho t HCl to Zn granules

(d) Simply add dil. HCl to Zn granules at room temperate

36.

If iron are added to ZnSO4 solution possible observation would be.

(a) No reation takes place

(b) Silvery cotting on iron nails

(c) Black cotting on iron nails

(d) Pale green colour of solution is seen

31. Which of the following is not a part of reflex arc:

(a) Sensory neuron

(c) Relay neuron

(b) Brain

(d) Spinal cord

32. Which hormone is not released from pituitary gland:

(a) Growth hormone (b) Oestrogen (c) Oxytocin (d) Prolactin

28.

A resistor is connected to an ammeter in series and a voltmeter in parallel to a source of energy. The quantity that cannot be found directly is:

(a) Current (b) Potential Difference

(c) Resistance (d) All of these

29.

Four different measuring instruments are shown below. Out of these, the instrument that can be used for measuring current is/are the instruments labelled as:

(f) I and III with III more reliable of the two.

(g) I and IV with IV more reliable of the two.

(h) II and III with II more reliable of the two.

(i) II and IV with IV more reliable of the two.

J.

Choose the incorrect statement from the following regarding magnetic lines of field:

The direction of magnetic field at a point is taken to be the direction in which the north pole of a magnetic compass needle points.

Magnetic field lines are closed curves.

In magnetic field lines are parallel and equidistant, they represent zero field strength.

Relative strength of magnetic field is shown by the degree of closeness of the field lines.

K.

Acid rain happens because:

Sun leads to heating of upper layer of atmosphere.

Burning of fossil fuels release oxides of carbon, nitrogen and sulphur in the atmosphere.

Electrical changes are produced due to friction amongst clouds.

Earth atmosphere contains acids.


SCIENCE (Theory)

Class – X

(Solutions)

SECTION-A nn) CaOCl

2 oo) Nephron.

3. P =

V

2 ⇒ P 

1

⇒ R 

1

R R P

Therefore 60 W bulb has a higher resistance.

48.

It is property due to which a crystalline substance loses water of crystallization when exposed to air and becomes amorphous, e.g.,

Na

2

CO

3

.10H

2

O  air  Na

2

CO

3

.H

2

O + H

2

O

5.

Tropic movements Nastic movements

(i) Direction of movement is in the direction (i) Direction of movement is not determined of the stimulus.

(ii) Movements are slow.

by the direction of stimulus.

(ii) Movements are fast.

Example:

The growth of the pollen tube towards a chemical produced by an ovule during the process of fertilization in a flower.

Example:

The folding up and drooping of leaves of the sensitive ‘touch-me-not’ plant.

9.

Lines indicating the presence of magnetic field in a region are called magnetic lines of force.

10.

Displacement reaction is a reaction in which more reactive element displaces less reactiveelements from its salts.

Example: 2KI

 aq



+ Cl

2

 g

  2KCl

It is a displacement reaction.

11.

Chemical formula is a formula of a compound formed with the help of symbols and valency ofelements and radicals.

Information conveyed by a chemical formula:

(b) It conveys the name of the compound.

 aq

(d) It conveys the valency of atoms present in it.



+ I

2

 g



(c) It conveys the number and kind of atoms present in one molecule of compound.

(jj) It represents the molecular weight of the compound.

(kk) It indicates that the compound is not electrically charged. It is neutral molecule. For example, formula CaCO

3 conveys following information:

(c) It stands for calcium carbonate.

(d) It represents the one mole of calcium carbonate. Two molecules of calcium carbonate would be written as 2CaCO

3

and so on.

(e) It tells that each formula of CaCO

3

contains 1 atom of Ca, 1 atom of C and 3 atoms of O.

(f) It stands for 100 parts by weight of CaCO

3

.

(40 + 12 + 3 x 16 = 40 + 12 + 48 = 100)

(g) The ratio among Ca : C : O is 40 : 12 : 48 by weight.

14.

(i) CO

2

is formed.

Na

2

CO

3

+ H

2

SO

4

(dil.)  Na

2

SO

4

+ CO

2

+

H

2

O (ii) SO

2

is formed.

S + 2H

2

SO

4

(conc.)  3SO

2

+ 2H

2

O

(iii) SO

2

+ Ca(OH)

2

 CaSO

3

+

H

2

O Lime water turns milky.

10.

(i) Mineral: It is naturally occurring substance from which a metal may or may not be extracted profitably, e.g., Borax is mineral from which boron cannot be extracted economically.

(ii) Ores: They are naturally occurring rocky substances which contain sufficient quantity ofminerals from which metals can be extracted profitably, e.g., Al is extracted from

Bauxite.

(iii) Gangue: They are rocky materials present in the ores along with the minerals, e.g.,

SiO

2 ispresent as gangue in ore of iron.

11.

(i) It is because metals can loss electrons easily to form positive ions, therefore regarded as electropositive elements.

(ii) It is because copper is less reactive than Zn, therefore, it cannot displace Zn from ZnSO

4 solution.

Cu + ZnSO

4

 No reaction

But when Zn is dipped in copper sulphate solution, it displaces copper from CuSO

4

to form

ZnSO

4

which is colourless. Reddish brown copper metal gets precipitated because Zn is more reactive than Cu.

Zn + CuSO

4

 ZnSO

4

+ Cu

Zinc (Blue) (colourless) Copper

(x) It is because oxide layer is formed on the surface of aluminum due to which it does not react further because it is non-penetrating layer.

12.

(iv) (a) Glottis is guarded by epiglottis to prevent food from entering the windpipe at the time of swallowing.

The lung alveoli are covered with blood capillaries for the easy diffusion of respiratory gases, since both alveoli and blood capillaries are thin-walled.

The wall of trachea is supported by cartilage rings so that it does not collapse when there is not much air in it.

(v) Male gonads are testes and female gonads are ovaries in human beings.

Functions of Testes:

(ii) Testes produce sperms, the male haploid gametes.

(ii) They produce male sex hormones, i.e., testosterone.

Functions of Ovaries:

(g) They produce ova, the female haploid gametes.

(h)

(vi) (a)

They produce female sex hormones i.e., estrogen and progesterone.

27.

R eq

= R

1

+ R

2

+ R

3

= 5 + 10 + 15 = 30 

V = V

1

+ V

2

+ V

3

+ V

4

+ V

5

= 2 + 2 + 2 + 2 + 2 = 10 V

 I =

V



10



30 3

1

A R eq

6 The strength of the magnetic field produced at the centre of a circular coil of radius r , having N turns and carrying a current I, is given by:

B =

 NI o

2 r

tesla

Thus the strength of the magnetic field in the coil is:

(i) inversely proportional to the radius of the loop.

B 

1 r directly proportional to the number of turns.



B  N

 directly proportional to the current passing through it.

(g) (a) Methane, Carbon di-oxide, Hydrogen and Hydrogen sulphide

(b) Advantages of biogas over fossil fuels:



B  I



(i) Biogas burns without smoke and does not cause air pollution while fossil fuel burns and causes air pollution.

(ii) Biogas does not leave any residue after burning while fossil fuel leaves residue like ash which have a disposal problem.

(iii) Biogas is cheaper than fossil fuel.

(h) (a) Solar panals

(b) Solar energy.

(c) Because Rajasthan gets a lot of sunshine throughout the year.

(d) Solar cell.

(e) General awareness, concern for the environment to improve it, desire to help people.

(i) The containers made up of copper or aluminium is suitable for storing the given solutions, can be decided by studying their reactions:

(i) Reaction of copper with

Dil. HCl. Cu + dil. HCl  No reaction.

So it can be stored in Cu container.

Dil. HNO

3

. Being a strong oxidizing agent, dil. HNO

3

reacts with copper, so it cannot be stored in copper container.

ZnCl

2

. Copper is less reactive than zinc so it does not react with ZnCl

2

solution.

Therefore it can be stored in copper container.

H

2

O. Copper does not react with water. So its container can store H

2

O in it.

(ii) Reaction of ALuminium with

Dil. HCl. Al reacts with Dil. HCl, so it can not be kept in aluminium container.

2Al + 6HCl  2AlCl

3

+ 3H

2

Dil. HNO

3

. When dil. HNO

3

is kept in Al container, it forms a protective layer of aluminium oxide on it, therefore it can be kept in Al container.

ZnCl

2

. Al is more reactive than zinc, so it cannot keep ZnCl

2

solution in it. 2Al + 3ZnCl

2

 2AlCl

3

+ 3Zn

H

2

O. Al does not react with water (hot or cold). Therefore water can be kept in Al container.

Aluminium is attracted by steam to form aluminium oxide and hydrogen.

2Al

 s



+ 3H

2

O

 g

  Al

2

O

3

 g



+ 3H

2

 g



Or

The reactions of zinc granules with various reagents are as follows:

(i) Dil. H

2

SO

4

Zn

 s



+ H

2

SO

4

 aq

  ZnSO

4

 aq



+ H

2

 g



(ii) Dil. HCl

Zn



2 Dil. HNO

3

Zinc sulphate

Dil. HNO

3

is an oxidizing acid so its reaction with a metal (e.g. Zn) is different than other dilute acids.

4Zn s



+ 2HCl

 aq

 s



+ 10 HNO



3



Zinc sulphate

ZnCl

2

 aq



+ H

 aq

  4ZN



NO

3

2





2 g



 aq



+ 5H

2

O

 l



+ N

2

O

 g



(iv) NaCl solution

Reaction does not take splace.

Zinc Nitrate

Zn

 s



+ NaCl

(v) NaOH solution

 aq

  No reaction

Nitrous oxide

Zn

 s



+ 2NaOH

 aq

  Na

2

ZnO

2

 aq



+ H

2

 g



Sodium zincate

Thus, hydrogen gas is evolved with H

2

SO

4

, HCl and NaOH, nitrous oxide gas is evolved with dilute HNO

3

and no reaction takes place with NaCl solution.

20. (a) ‘Activity series’ of metals is the series in which metals are arranged in decreasing order of their reactivities.

Mg > Al > Zn > Fe > Cu is in a decreasing order of reactivity.

(b) (i) When zinc is placed in copper sulphate solution, the solution becomes colourless and brown colour copper metal is depicted.

Zn

 s



+ CuSO

4

 aq

  ZnSO

4

 aq



+ Cu

 s



(ii) Copper does not react with ferrous sulphate because it is less reactive than iron. No change takes place.

(f) Sodium metal combines with hydrogen to form Sodium hydride.

2Na + H

2

 2NaH (Sodium hydride)

Or

32.

Froth Floatation process: It is the process to concentrate sulphide ore. The ore is mixedwith water and pine oil and mixture is agitated with the blast of air. Froth is formed.

Sulphide ore gets collected in froth whereas impurities are left behind e.g., Zinc Blende

(ZnS) is concentrated by Froth Floatation process.

33.

Roasting of an ore: The process of heating sulphide ore in presence of oxygen so as to convert it into oxide is called roasting, e.g.,

2ZnS + 3O

2

 2ZnO + 2SO

2

(e) Calcination of an ore: It is defined as heating of ore in absence of oxygen so as to convert it into oxide, e.g.,

ZnCO

3

 heat ZnO + CO

2

JJ.

Photosynthesis is a process in which plants use sunlight, chlorophyll, Carbon di-oxide andwater to synthesize food.

It occurs in two stages:

Light reaction: During this reaction ATP and NADPH are generated. This step is lightdependent.

Dark reaction: It is not dependent on light. During this reaction, carbon di-oxide isproduced to carbohydrate. Source of energy is ATP and NADPH.

Factors affecting rate of photosynthesis process:

(i) Light: Rate of photosynthesis increases at the low intensities and decreases at its higherintensities.

(ii) Temperature: Low and high temperature has inhibitory effect on the rate ofphotosynthesis.

(iii) Water: The rate of photosynthesis will become slow under water deficient conditions.

(iv) Carbon dioxide: the rate of photosynthesis increases with an increase in

CO

2 concentration up to a certain level beyond that it may prove inhibitory.

Or

Difference between Respiration in plants and Respiration in animals:

Respiration in plants Respiration in animals

(i) Plants do not have respiratory system.

(i) Animals have respiratory system.

(ii) Direct diffusion of respiratory gas into (ii) The respiratory gases are transported up the cells.

to the tissue cells.

(iii) Plant respiration occurs at slower rate.

(iii) Animal respiration occurs at faster rate.

Gaseous exchange through root hair in plants:Roots take up oxygen present in between the soil particles by the process of diffusion. Root hairs, the extension of epidermal cells of root are in contact with oxygen in the soil. Oxygen diffuses into root hairs and passes into other cells of the root. Carbon dioxide from root cells moves out into the soil. Thus, root hair provide increased surface area for gaseous exchange.

22.

(i) According to Joule’s law of heating, the heat H produced in a wire of resistance R while carrying a current I in time ' t ' is directly proportional to the square of current, resistance and time.

H = I 2 R t

Proof: Work done to carry a charge dq against a potential difference V is, d

W = V dq  VI dt ⇒ W = VI t = I

2

R t

This work done is dissipated as heat energy.

(ii) Commercial unit is kWh.

1 kWh = 3.6

 10

6 joules

(iii) Resistance of 40 W bulb =

220

2

220 2

40

Net resistance = 4 x

= 4840 

40

Current drawn and flowing through them = I =

220



220

= 0.045 A

R 4840

If one bulb fuses, no current flow will be seen in them.

Or

(a) Since resistivity depends neither on the length nor on the cross-sectional area of the conductor, the resistivity will remain unaffected in all variations. Also here material is same.

(b)

23.

Electrical energy used by:

(a) 4 bulbs of 60 W = 4 x 60 x 6 x 30 = 43200 Wh

(b) 3 tubelights of 40 W = 3 x 40 x 8 x 30 = 28800 Wh

(c) 300 W refrigerator = 300 x 24 x 30 = 216000 Wh

(d) 750 W mixer = 750 x 1 x 30 = 22500 Wh

(e) TV of 100 W = 100 x 6 x 30 = 18000 Wh

Net energy consumption = 328500 Wh = 328.5 kWh = 328.5 units Cost for first 50 units = 2.50 x 50 = Rs.125.00

Cost for the remaining units = 3.00 x 278.50 = Rs.835.50

Total cost of electricity consumed = Rs.960.50

Or

(i) Series

Net resistance = R

60

+ R

H

Where R

60

is the resistance of 60 W bulb and R

H

is the resistance of the heater.

Heat produced with a source of potential V (H) =

V

2

R t

60

+ R

H

R

100

– Resistance of 100 W bulb is less than that of R

60

.

 Heat produced in same time ' t ' should be more with 100 W bulb than with 60 W bulb.

(ii) Parallel

Net resistance in parallel will be, R =

R

60

R

H

R

60

+ R

H

This will be less than R

60

and R

H

.

Heat produced, H =

V

R

2 t

If 60 W is replaced by 100 W bulb, the resistance R will further reduce. So heat produced will be increased.

24. (a) Magnetic field: Surrounding a magnet its influence is felt by any other magnetic element. It may be an attractive of a repulsive influence.

(b) The direction of magnetic field at a point is determined by drawing a tangent at that point. The direction of tangent gives the direction of magnetic field.

(c) Aim: To demonstrate the direction of the magnetic field generated around a currentcarrying conductor.

Procedure:

(i) Obtain the concentric circles pattern of iron fillings around the copper wire by flowing current through it as shown.

(ii) Place a magnetic needle (compass) at any point (P) over a circle.

(iii) Observe the direction of needle.

(iv) Show the direction by arrows.

Conclusion: The direction of the north pole of the compass needle would give the directionof the field lines produced by the electric current through the straight wire at that point. The direction

of the field is perpendicular to the plane of the coil and directed inwards forthe clockwise current flowing. For anticlockwise current, it will be outwards.

Or

Pure iron is not used for making permanent magnets because it cannot retain their magnetism for long time and used only for electromagnet since alloys of iron and steel have strongly magnetized and have a capacity to hold it for a longer time period, they are used for permanent magnets.

Material used for permanent magnets – ALNICO

Formation of a permanent magnet electrically: Permanent magnets can be formed byplacing a hard steel rod in the strong uniform magnetic field produced by the solenoid. Steels have the quality to retain its magnetism after switch off the solenoid current.

Permanent magnets are used in:

(i) Galvanometer (ii) Ammeter

25.

The solution remains colourless because HCl is acid and It does not react with phenolphthalein.

26.

(a) Transpiration.

(b) Water loss due to evaporation from the plane is called transpiration.

27.

No change will be there i.e. the resistivity '  ' will be same because it is a material constant.

28.

(b)

29.

(d)

30.

(b)

31.

(b)

32.

(b)

33.

(c)

34.

(a)

35.

(c)

36.

(b)

Paper 5


SCIENCE (Theory)

Class – X


General Instructions: pp) All questions are compulsory. qq) The question paper comprises of two sections, A and B. You are to attempt both the sections. rr) Questions 1 to 3 in section A are one mark questions. These are to be answered in one word or in one sentence. ss) Questions 4 to 6 in section A are two marks questions. These are to be answered in about 30 words each. tt) Questions 7 to 18 in section A are three marks questions. These are to be answered in about

50 words each. uu) Questions 19 to 24 in section A are five marks questions. These are to be answered in about

70 words each. vv) Questions 25 to 27 in section B are 2 marks questions and Questions 28 to 36 are multiple choice questions based on practical skills. Each question of multiple choice questions is a one mark question. You are to select one most appropriate response out of the four provided to you.

Section A

49.

What happens when a chemical reaction occurs?

50.

Name the two stages of photosynthesis.

51.

What is meant by the statement, “Potential difference between points A and B in an electric field is 1 volt”?

52.

(a) What is observed when sulphur dioxide is passed through (i) water, (ii) limewater?

(a) Also write chemical equations for the reactions that takes place.

53.

Name the hormone responsible for regulation of:

(b) Metabolism of carbohydrates, fats and proteins.

(a) Balance of calcium and phosphate.

(b) Blood pressure.

(c) Water and electrolytic balance.

16 With the help of neat diagram describe how you can generate induced current in the circuit.

23.

Identify the substances oxidized and the substances reduced in the following reactions. Write the ionic equation for the substances oxidized and reduced.

(a) H

2

 g



+ Cl

2

 g



 2HCl

 g



(b) H

2

 g



+ CuO

 s

  Cu

 s



+ H

2

O

 l



(c) H

2

S

 g



+ SO

2

 g



 S

 s



+ H

2

O

 l



24.

2FeSO

4

 s

  Fe

2

O

3

 s



+ SO

2

 g



+ SO

3

 g



. Is it a redox reaction or not? If yes, why?

25.

(a) Write the formula and chemical name of Bleaching powder.

Write chemical equation to represent the action of atmospheric CO

2

gas on bleaching powder when left exposed in open.

State for what purpose is bleaching powder used in water treatment plants.

20.

Mrs. Sharma has gone to the jewelers to buy gold jewellery. She asks the jeweler if the jewellery is made of pure gold. The jeweler assure her that it is 10% gold and nothing has been mixed in it. Mrs. Sharma is happy and buys the necklace.


(b) Was the jeweler right in saying that the necklace is made of 100% gold?

(c) What values are promoted by the jeweler?

(d) What precautions should you take while purchasing gold jewellery?

(e) Why does Government insist on purchasing Hallmarked jewellery?

[Value Based Questions]

29.

Describe with labelled diagram, Explain electrolytic refining of copper metal.

30.

(a) Draw diagram of a Stomata when it is open.

Label Epidermal cell, Guard cell, Chloroplast and Stomatal opening on the diagram drawn.

31.

Write the functions of the following in the digestive process:

(c) Bile

(d) Bicarbonate secreted by the duodenal wall.

(e) Pancreatic amylase.

19.

What are ‘hormones’? Write any two functions of hormones.

20.

(a) State Ohm’s law.

(b) Draw a schematic diagram of the circuit for studying Ohm’s law.

21.

The flow of a current in a circular loop of wire creates a magnetic field at its centre. How many existence of this field be detected? State the rule which helps to predict the direction of this magnetic field.

20.

(a) Describe the steps involved in obtaining biogas and explain what is meant by anaerobic decomposition.

(b) Which isotope of Uranium can undergo fission readily?

21.

(a) State one limitation of solar energy available from solar cells.

(b) What is the minimum wind velocity required to obtain useful energy with a wind mill.

(c) Define the term ‘Nuclear fission’.

22.

Identify the type of chemical reaction taking place in each of the following:

Barium chloride solution is mixed with copper sulphate solution and a white precipitate is observed.

22.

On heating copper powder in air in a China dish, the surface of copper powder turns black.

23.

On heating green coloured ferrous sulphate crystals reddish brown solid is left and small of a gas having odour of burning sulphur is experienced.

24.

Iron nails when left dipped in blue copper sulphate solution become brownish in colour and the blue colour of copper sulphate fades away.

25.

Quick lime reacts vigorously with water releasing a large amount of heat.

Or

During the reaction of some metals with dilute hydrochloric acid, following observations were made:

(i) Silver metal doesn’t show any change.

(ii) The temperature of reaction mixture rises when aluminium (Al) is added.

(iii) The reaction of sodium metal is found to be highly explosive.

(iv) Some bubbles of a gas are seen when lead (Pb) is reacted with the acid.

(v) A gas produced when sodium carbonate is added to the acid.

Explain these observations giving suitable reasons.

29.

Give reasons for the following:

Metals conduct electricity.

Metals generally do not form compounds with hydrogen.

A piece of zinc placed in blue copper sulphate solution decolourize it.

Alumina is dissolve in molten cryolite for electrolysis to obtain aluminium metal.

Nitrogen gas is used to preserve food.

Or

(ix) What is corrosion of metals? Name one metal which does not corrode and one which corrodes on being kept in atmosphere.

(x) How will you show that the rusting of iron needs oxygen and moisture at the same time.

38.

(a) Draw a diagram of human alimentary canal.

37.

Label oesophagus, Liver, Pancreas and Gall bladder on the diagram drawn.

38.

What is the function of enzyme ‘pepsin’ in the digestion process?

Or

(a) Draw a diagram of the human urinary system and label on it:

(i) Kidney (ii) Ureter (iii) Urinary bladder (iv) Urethra

(b) Name the two major components of normal human urine. b (a) What is the function of an earth wire in electrical instruments? Why is it necessary to earth the metallic electric appliances?

(ii) Explain what is short circuiting and overloading in an electric supply.

(jj) What is the usual capacity of the fuse wire in the line to feed:

Lights and fans?

(ii) Appliances of 2 kW or more power?

Or

State Ohm’s law.

Describe the activity with the help of a diagram to establish the relationship between current (I) flowing in a conductor and potential difference (V) maintained across its two ends.

Draw the shape of the curve obtained when a graph is plotted between I and V.

23.

(a) What is meant by a magnetic field?

(b) How is the direction of magnetic field at a point determined?

(c) Describe an activity to demonstrate the direction of the magnetic field generated around a current carrying conductor.

(d) What is the direction of magnetic field at the centre of current carrying circular loop?

Or

(a) What is an electromagnet?

(b) List any of its two uses.

(c) Draw a labelled diagram to show how is an electromagnet made?

(d) What is the purpose of the soft iron core used in making an electromagnet?

24.

(a) Distinguish between renewable and non-renewable sources of energy giving one example of each.

(b) Why is the use of wood as a fuel not advised although forests can be replenished?

Or

Explain why:

35.

It is difficult to burn a piece of wood fresh from a tree.

36.

Pouring dry sand over the fire extinguishes it.

37.

It is difficult to use hydrogen as a source of energy.

38.

Charcoal is considered a better fuel than wood.

Section B

37.

In test tube A the solution turns blue litmus red evolves H

2

gas with Zn metal gives out CO

2

on treatment with

Na

2

CO

3

. In test tube B the solution turns red litmus blue, liberate H

2

with Zn metal and does not react with Na

2

CO

3

.

What are A and B? Give the chemical reactions involved.

26.

(a) In plant, when stomata is opened in night, are called _________.

(b) Justify your answer.

27.

Why key used in electric circuit should be kept off? Give reason.

28.

The pH of soft drink is _______ and they are _______.

(a) less than 7, acidic (b) more than 7, basic

(c) equal to 7, neutral (d) less than 7, basic

29.To study the reaction between HCl and Zn student has to :

(a) (a) Heat the mixture

(b) (b)Add HCl on hot Zn granules

(c) (iii)Add ho t HCl to Zn granules

(d) (D) Simply add dil. HCl to Zn granules at room temperate

(e)

(f)

30. If iron are added to ZnSO4 solution possible observation would be.

(a)No reation takes place

(b)Silvery cotting on iron nails

(g) (c)Black cotting on iron nails

(h) (d)Pale green colour of solution is seen

31. Sunlight used for photosynthesis is:

(a) 5% (b) 50% (c) 0.5% (d) 4%

32.

The process in which water is split during photosynthesis is called:

(a) Photolysis (b) Hydrolysis (c) Glycolysis (d) None of these

33.

Ammeter is always connected in:

(a) Series

(c) Either in series or parallel

34.

For current flow one need a:

(a) Closed circuit

(c) Both (a) and (b)

(b) Parallel

(d) Neither in series nor in parallel

(b) Source of potential difference

(d) Neither (a) nor (b)

35.

A voltmeter connected in parallel to a resistor reads 0.1 volt. There is:

(a) Zero error (b) Positive error (c) Negative error (d) Both (b) & (c)

36.

Which of the following is a non-renewable source of energy:

(a) Wood (b) Sun (c) Fossil fuels (d) Wind


SCIENCE (Theory)

Class – X

(Solutions)

SECTION-A ww) When a chemical reaction occurs, new products are obtained. xx) Light reaction and Dark reaction. yy) Work done to carry a unit positive test charge from A to B is 1 Joule. zz) (a) Sulphurous acid is formed.

SO

2

+ H

2

O  H

2

SO

3

(Sulphurous acid}

(b) Limewater turns milky due to formation of calcium sulphate.

SO

2

+ Ca(OH)

2



5. (i) Thyroxine hormone

CaSO

3

+ H

2

O

(ii) Calcitonine hormone

(iii) Adrenaline hormone (iv) Vasopressin hormone

54.

Connect a coil AB of wire having a number of turns. Connect it to a sensitive galvanometer as shown in figure.

Move a bar magnet towards the coil. When North Pole is taken fast towards or South Pole is taken fast towards the coil, the deflection occurs in the galvanometer but will be in opposite direction. When the coil and magnet both are stationary, there is no deflection in the galvanometer. Thus the motion of a magnet, with respect to the coil, produces an induced potential difference which sets up an induced electric current in the circuit.

11.

(a) H

2

 2H

  2 e

 (Oxidation)

Substance getting oxidized is H

2

.

Cl

2

 2 e

  2Cl



(Reduction)

Substance getting reduced is Cl

2

.

12.

Cu 2   2 e

  Cu

(Reduction) Substance getting reduced is Cu. H

2

 2H

2 e

 (Oxidation)

 


2

.

13.

2S 2

2

  2S + 4 e



(Oxidation)


2

S.

S 4   4 e

  S (Reduction)

Substance getting reduced is SO

2

.

(iv) It is a redox reaction because Ferrous



Fe 2 



is getting oxidized to Ferric



Fe 3 



whereas

SO 2

4

 is getting reduced to SO

2

.

(v) (a) CaOCl

2

, Calcium oxychloride

CaOCl

2

+ CO

2

 CaCO

3

+ Cl

2

It is used as disinfectant in water treatment plants.

(vi) (a) No, he was wrong. Pure gold is very soft and is therefore not suitable for making jewellery.

It is alloyed with either silver or copper to make it hard. But sometimes jewelers mix a large quantity of copper and silver in gold to earn more profit.

(b) Untrustworthiness, cleverness.

(c) We should always purchase the gold jewellery from a branded shop with proper receipt and Hallmark certificate.

(d) Government insists on purchasing Hallmarked jewellery as it contains the gold and its alloyed metal (i.e. copper or silver) in a fixed ratio.

12.

13.

The functions of the following in the digestive process are:

(b) Bile: Bile in the duodenum emulsifies fat present in the food, i.e. breaks fat molecules intosmall globules.

(c) Bicarbonate secreted by the duodenal wall: Bicarbonate ions secreted by the duodenalwall mke the medium alkaline because such a medium is required for the action of pancreatic enzymes.

(d) Pancreatic amylase: Pancreatic amylase acts on starch and hydrolyses it into maltose andisomaltose.

14.

‘Hormones’ are chemical substances secreted in trace amounts by specialized tissues called endocrine glands.

The two functions of hormones are as follows:

Hormones coordinate the activities of the body and also its growth.

(iii) Hormones regulate many functions like metabolism and reproduction in our body.

(vi) (a) Ohm’s law: Under similar physical conditions, such as temperature remains constant, the current flowing through a wire is directly proportional to the difference in potential applied across its ends, i.e., I  V.

or V = IR where R is the resistance offered.

(b)

24.

To detect the presence of the magnetic field created by the current in a circular loop at the centre, one can draw the magnetic field lines with the help of compass needle. The magnetic field lines appear as a straight line at the centre and other lines appear in the same direction without the loop.

Right hand thumb rule: Hold the wire in your right hand with your extended thumb pointing in the direction of current. Your folded fingers will indicate the direction of magnetic field around the wire.

23.

(a) Anaerobic decomposition: The process in which the complex compound of cow dung slurry decomposes or breaks down in the absence of oxygen by anaerobic micro organisms called anaerobic bacteria is known as anaerobic decomposition.

Steps involved in obtaining biogas:

Slurry is made by mixing of animal dung with an equal amount of water.

Slurry is passed through an inlet chamber of an underground digester tank.

In digester tank, slurry is decomposed by anaerobic bacteria in about 50-60 days to produce biogas.

The biogas collected in domes built over the digester tank and has a gas outlet with valve.

The pressure exerted by the biogas on the slurry forces the spent slurry to the overflow tank via outlet chamber.

The spent slurry is periodically removed and used as a good manure.

The whole process is repeated again for regular supply of biogas.

(c)

92

235 U can undergo fission readily.

24.

(a) Conversion efficiency is less.

Approximately 15 km/h.

The process in which the heavy Uranium nucleus splits into lighter nuclei of smaller atomic numbers is called Nuclear fission.

92

235 U + 1

0 n  141

56

Ba + 92

36

Kr + 3 1

0

n + Q

Q refers to the energy of 200 MeV released.

.

27.

(a) Double displacement reaction, precipitation reaction.

(a) Combination reaction, oxidation reaction.

(b) Thermal decomposition

(c) Displacement reaction

(d) Combination and exothermic reaction

Or

30.

Silver is very less reactive metal. So it does not react with dilute HCl.

31.

The reaction of Al with dilute HCl is exothermic i.e. heat is produced in the reaction, so the temperature of the reaction mixture rises.

32.

Sodium is a very reactive metal. It react vigorously with the evolution of heat too.

33.

Bubbles are seen due to the evolution of H

2

gas.

Pb

 s



+ 2HCl

 aq



 PbCl

2

+ H

2

 g



(v) CO

2

gas is produced when Na

2

CO

3

reacts with dilute HCl.

Na

2

CO

3

 s



+ 2HCl

 aq

  2NaCl

 aq



+ H

2

O

 l



+ CO

2

 g



30.

(a) It is due to presence of free electrons.

(b) Metals are good reducing agents and H

2

is weak oxidizing agent therefore, metals do not react with hydrogen to form hydrides.

(j) Zn + CuSO

4

 ZnSO

4

+ Cu

It is due to formation of ZnSO

4

(aq) which is colourless.

(k) It increases electrical conductivity and molten cryolite acts as a solvent.

(l) It prevents oxidation of food which prevents its spoilage.

Or

(a) Corrosion of metal is a process in which metal reacts with substances present in atmosphere to form surface compounds. ‘Al’ does not corrode whereas ‘Fe’ corrodes when placed in atmosphere.

(b) Take three test tubes and put iron nails in each of them. In the first test tube add H

2

O up to brim and leave no space for air. In the second test tube add fused CaCl

2

so as to absorb moisture. In the third test add water and leave space for air. Leave them for few days.

Rusting will not take place in first and second test tubes. But rusting will take place in third test tube showing that rusting of iron requires both air and moisture.

39.

The function of the enzyme ‘pepsin’ in the digestion process is that it breaks down proteins into peptones in acidic medium of gastric juice.

Or

(i)

(c) The two major components of normal human urine are water and nitrogenous substances, most of which is urea.

27.

(a) The earth wire helps us by offering a low resistance path to the high potential that might have come in contact with the body or other unwanted part of the device. This will not bring any damage to the device or to the person handling the device. The fuse may disconnect the electrical link in such cases.

Overloading is the situation which causes a sudden draw of larger current by the electrical appliances, when operated at the same time from a single parallel connection.

In short-circuit the live wire comes in contact with the neutral line. This gives a large drop of potential and flow or current through the fuse wire. So it burns.

(c) (i) 5 A (ii) 15 A

Or

(a) Ohm’s law: The electrical current (I) flowing through a metallic wire is directly proportional to the potential difference (V) across its ends provided the physical conditions like temperature remains constant.

Mathematically: V  I ⇒ V = IR

26.

Aim: To establish the relationship between potential difference across the resistor andcurrent passing through it.

Apparatus required: Nichrome or eureka wire (length 0.5 m) , an ammeter, a voltmeterand four cells if 1.5 V each.

Procedure: i Set the circuit as shown in the figure. ii First use only one cell as the source and note the reading of the ammeter and voltmeter. iii Now connect two cells in series and note the reading of the ammeter and voltmeter again. iv Now connect three cells in series in the circuit and again take the reading of both devices. v Lastly connect fourth cell in series in the circuit also note the reading of the ammeter and voltmeter again.

Observation: In this activity, we will observe that the current increases with potentialdifference, i.e. more cells being connected in series. We will get approximately the same value for

V

in each case and we will also obtain straight line graph of V vs I passing

I through the origin as shown in figure. From the graph, we observe that

V

I

= constant, i.e. V = constant x I or V  I

Conclusion: The constant is called Resistance. If we change the wire, the graph will varybut remain a line with a different slope/resistances.

(c) Shape of the V-I curve is a straight line passing through the origin as shown in figure.

23. (a) Magnetic field: Surrounding a magnet its influence is felt by any other magnetic element. It may be an attractive of a repulsive influence.

4 The direction of magnetic field at a point is determined by drawing a tangent at that point.

The direction of tangent gives the direction of magnetic field.

5 Aim: To demonstrate the direction of the magnetic field generated around a currentcarrying conductor.

Procedure:

(a) Obtain the concentric circles pattern of iron fillings around the copper wire by flowing current through it as shown.

(b) Place a magnetic needle (compass) at any point (P) over a circle.

(c) Observe the direction of needle.

(d) Show the direction by arrows.

Conclusion: The direction of the north pole of the compass needle would give the directionof the field lines produced by the electric current through the straight wire at that point.

37.

The direction of the field is perpendicular to the plane of the coil and directed inwards for the clockwise current flowing. For anticlockwise current, it will be outwards.

Or

(a) Magnetizing a material: When a material like soft iron, is placed inside a coil carryingcurrent (may be a solenoid), it will get magnetized. Once the current is put-off, the magnetic field will also be lost. Such magnets are called electromagnets.

(b) Two uses of electromagnet:

(i) In electric bells.

(ii) For sorting scrap metal.

(c)

The purpose of soft iron core used in making an electromagnet that:

It is temporary magnetized.

It retains magnetism as long as current flow is maintained.

It will ensure an uniform and stronger field.

38.

(a) Renewable sources of energy are those that can be used without depleting their reserves and do not get exhausted. E.g., solar energy, wind energy, hydro energy etc.

Non-renewable sources of energy are those which cannot be replenished and exhausted with the passage of time, e.g. coal, petroleum and natural gas.

(a) Wood is not advisable used as a fuel, although forests can be replenished due to the following reasons:

Burning of wood causes pollution.

The left-over residue after combustion have a disposed off problem.

Smoke produced by burning of wood caues health hazard.

Wood is a less heat generating fuel.

Trees are essential for our life as they absorb

CO2

and give out O

2

.

Or

(a) It is because a piece of fresh wood is not dry and therefore it is to be heated at high temperature before it catches fire that is why it is difficult to burn.

(b) It cuts off the supply of air (oxygen) which is required for combustion to take place.

(c) Hydrogen is highly combustible and burns with an explosion, therefore, it is difficult to store and transport.

(d) Charcoal, has higher calorific value than wood and produces less smoke than wood.

29.

‘A’ is HCl because it turns blue litmus red and liberates H

2

with Zinc and CO

2

with Na

2

CO

3

.

Zn + 2 HCl  ZnCl

2

+ H

2

Na

2

CO

3

+ 2HCl  2NaCl + CO

2

+ H

2

O

‘B’ is NaOH because it turns red litmus blue and liberates H

2

gas with Zinc metal.

Zn + 2 NaOH  Na

2

ZnO

2

+ H

2

Na

2

CO

26.

(a) Scotoactive

3

+ NaOH  No reaction

(b) Due to deficiency of oxygen, in most plants, stomata opens at night, e.g., Opuntia,

Bryophyllum.

27.

Key used in electric circuit should be kept off to avoid heating of the resistor because heating changes resistance.

28.

(a)

29.

(d)

30.

(b)

31.

(a)

32.

(a)

33.

(a)

34.

(c)

35.

(b)

36.

(c)

Paper 6

SAMPLE PAPER NO 1 (SA-I)

Subject- Science

Class –X Maximum Marks 90 Time :- 3Hrs.


1.The question paper comprises of two sections A and B .You are to attempt both the section.

2. All questions are compulsory.

3. There is no overall choice. However, internal choice has been provided in all the five questions of five marks category. Only one option in each question is to be attempted.

4. All questions of section A and all questions of section B are to be attempted separately.

5. Question No. 1 to 3 in section A are one mark question. These are to be attempted separately.

6. Question No. 4 to 6 are two marks question, to be answered in about 30 words each.

7. Question No. 7 to 18 are three marks question. To be answered in about 50 words each.

8. Question No.19 to 24 are five marks questions. To be answered in about 70 words each.

9. Question No.25 to 33 in section B are multiple choice based on practical skills. Each question is a one mark question. You are to choose one most appropriate response out of the four provided to you.

10. Question No. 34 to 36 in section B are question based on practical skills are two marks questions.

Section –A

1.

Give an example of a metal which can be cut with knife.

2.

Write a balance equation to represent the following reaction:-Aluminum reacts with copper chloride to give aluminum chloride and copper.

3.

State and define the unit of current.

4.

Name the respiratory organs of (a) Fish (b) Mosquito (c) Earthworm (d) Dogs

5.

Surface of some metals loose their brightness when they kept in air for a long time.

Why?

6.

The atomic no. of sodium is 11, fluorine is 9 and Neon is 10. Why are sodium and fluorine very reactive while Nein show almost no reactivity?

7.

Although bile juice has no digestive enzyme. It is still considered to be very important for digestion of food .Give two reasons.

8.

Define neutralization reactions. Give an example in daily life application .

9.

Describe an activity to show that acid produce ions only in aqueous solution.

10.

What is osmoregulation? How does it takes place in human beings ?

11.

Define phototropism. Which hormone is responsible for it . How?

12.

Calculate the number of electrons that will constitute a flow of charge 5 C.( charge of one electron is 1.6*10 -19 C.

13.

what is bio gas? How is it produced . Mention one feature of bio gas that make it an ideal fuel.

14.

(a) classify the following reaction into different types-

(i) AgNO

3

+NaCl(aq) ->AgCl(s) +NaNO

3

(aq)

(ii) CaO(s) +H

2

O->Ca(OH)

2

(iii) 2KClO

3

(s) -> 2KCl+3O

2

(b) which of the above reaction is/are precipitation reaction ? why i9s the reaction called precipitation reaction?

15. When water is added to a white powder ‘A’ vigorous reaction t akes place & a large amount of heat is released. ‘A’ is also used for white washing.

(a). identify the ‘A’

(b)give the balanced equation.

(c )give the name and formula of the product.

16.Apiece of wire having resistance R is cut into four equal parts –

(a) How does the resistance of each part compared with the original resistance.

(b) If four parts are joined together in parallel , how will resistance of combination with the resistance of original wire ?

17 .What is meant by the term of magnetic field lines ?list any two properties of field lines.

18 .An electric room heater is rated at 2KW .calculate the cost of using it for 2 Hrs. daily for the month of September ,if each unit cost is 4 Rupees.

19. Mention the name of secretory part / gland and function of following hormones.-

(a) Insulin

(b) Progesterone

( c )Oxytocin

20. A person has lost his control over muscular activities.

a) What can be the possible cause?

b) What would you advice the person to overcome the problem?

c) Which value is inculcated?

21.(a) Give two example of renewable & non- renewable energy sources.

(b) Why is there need for harnessing non-conventional sources of energy.

( c ) Write the name of eco-friendly energy sources.

22. Find out the following in the electric circuit given in the figure-

(a) Potential difference across 4 ohm resistance

(b) Difference in ammeter reading if any of A1 & A2

23. ( a) Explain inn brief the mechanism of circulation of blood circulation of blood in human body.

(b) Lymph is another type of fluid involved in transportation. Justify the statement by two reason.

OR

(a) Explain the excretory system in human beings.(see fig.6.13 page no.110 NCERT textbook)

(b) List any two strategies used by plants for excretion.

24. Give reason for the following –

(a) melting point of ionic compounds are high

(b) Aluminum is more active then iron yet there is less erosion of aluminium when boith are exposed to air.

( c )Solder is used for welding electricals wires together

(d ) a sulphide ore is converted into its oxide to extract the metal .

(e) turnished copper vessels are cleaned with tamarind juice.

OR

(a) Write balanced chemical equation for reaction taking place when –

(i) Zinc carbonate is calcinated

(ii) Zinc sulphide is roasted

(iii)

(iv)

Zinc oxide is reduced to zinc

Cinnabar is heated in air

(v) Manganese dioxide is heated with aluminum powder

SECTION :-B

25. What observations can be made after zinc granules are added to a test tube containing dilute HCl ?

26. What observations be made when : a) Lead nitrate is heated? b) CaO is added to water ?

27. What precautions are required for setting up the experiment “ to show that CO

2

is

given out during respiration “ ?

28. Bottle A contain acetic acid and bottle B contain sodium carbonate solution. When pH paper is dipped in each of the solution, the colour seen in A and B respectively will be: a) blue, orange b) orange, green c) orange, blue d) green ,blue

29. On putting of few drops of a liquid on pH strip the colourofpH strips change to green , the liquid is most probably

(a) Lemon juice3

(c) NaOH solution

(b) Dilute HCl

(d) Water

30. Colourless gas is liberated when HCl acid is added to a solution of washing soda, the name of gas is

(a) Carbon di oxide

(c) Sulphur di oxide

(b) Nitrogen di oxide

(d) Sulphur tri oxide

31. The colour of metal deposited when iron nails are dipped in aqueous solution of copper sulphate is (a)reddishbrowen (b) Green

(c) Grey (d) Silvery white

N22229

32. What is the least count of following voltmeter

(a) 0.5 volt (b) 0.1 volt

(c) 0.05 volt (d) 0.005 volt

33. A solution of ammonium chloride is

(a) Acidic (b) Basic

(c) Neutral (d) Amphoteric

34. The equivalent resistance of 4 ohm, 5 ohm ,2 ohm, is 6.33 ohm. Then how can they be connected z

(a) 1 b) 2 c)3 (D) None of these

35. In given circuit voltmeter reading will be

(a) 0 volt (b) 5 volt (c) 1 volt (d) 2 volt

36. The oxygen evolved during photosyntheciscome from

(a) Spliting of carbon di oxide (b) From air

(c) Splitting of water (d) None of above

MODEL ANSWERS SAMPLE PAPER NO 1(SA-I)

Section –A

1. Sodium(Na)

2.2Al +3Cucl

2 

2AlCl

3

+ 3Cu

3. Ampere, if 1C of charge flows in 1second then current is said to be 1A.

4. (1) gills (2) Trachea (3) Skin (4) lungs

5. This is due to formation of undesirable compound such as oxides, Sulphide,

Carbonates on the surface of metals due interaction with air & moisture.

6. Na=2,8,1Ne=2,8 F=2,7

Sodium Na & fluorine F have tendency to lose or gain electrons to complete their

Octet.Where as Ne has its Octet complete and is extra stable

7. (1) Bile juice helps in to emulsify fat.

(2) Due to basic nature it neutralizes the acidic traces reaching the small intestine.

8. Reaction between acid & base gives salts & water and release energy that is

Neutralization.

Reaction: HCl + NaOH



H

2

O + NaCl + Energy

Antacid (Mg(OH)

2

) is used to cure acidity in stomach.

9. Heat a pinch of NaCl with con.H

2

SO

4 in a test tube

.

Pass HCl gas on dry blue

Litmus paper no change in colour takes place. Now pass HCl through blue litmus solution it turns red. This is because in aqueous solution H + ions produced.

10. Balance the water & salt level in body is called osmoregulation. It takes place nephron by the ADH (anti diuretic hormone). It effects the permeability of cells of nephron for absorption of water.

11. The growth movement of plants induced by stimulus of light is called phototropism.

Auxins hormone is responsible for it.High amount of Auxins is present in shady or dark half region of shoot apex which causes high growth & turns the plant towards light source.

12. 1electron=1.6*10 -19 C

1C=1/ 1.6*10 -19

5C=5/ 1.6*10 -19

=3.12**10 -19

13.The fuel gas produced by the animals & plant waste is called bio gas which contains methane. It is non polluting& has high calorific value.

14. (a) 1. Double displacement reaction

2. Combination reaction

3. Decomposition reaction

(b) Double displacement reaction is a precipitation reaction because in this

Reaction one insoluble product settles down at the bottom of test tube& get

Separated from soluble product.

15. A is calcium oxide CaO

CaO +H2O-- Ca (OH)

2

16. (a) Resistance of a wire is proportional to its length. Therefore cut into four pieces, resistance of each pieces will be R/4.

(b) When 4 pieces each of resistance R/4 are connected parallel, the combined

Resistance will be R’

1/R’=1/R/4+1/R/4+1/R/4+ 1/R/4

1/R’=4/R+4/R+4/R+4/R

1/R’=16/R

R’=R/16

17. Intensity of magnetic field around a bar magnet is shown by lines that are called

Magnetic field lines.

1. They emerge from north pole& enter S pole

2. Two magnetic lines of force never intersect each other

18. P=2KW=2000W t=60Hrs September=30days

Energy Units consumed= P*T/1000

=2000*60/1000=120KWH/Unit

Total Cost=120*4=480Rs.

19 (1) Insulin – beta cells of pancreas, control sugar level

(2) Progesterone – carpus leutium of ovary, maintains pregency& fixes the embryo touterus wall.

(3)Oxytocin – Pitiutary gland, milk secretion, birth hormone

20.a)Cerbellum control is lost due to taking of excess of alcohol

b) Advice – Not to take alcohol

c) Value- concern for human life

21.a) Renewable – wind , solar energy

Non Renewable – coal, petroleum, natural gas

b) Sources of fossils are limited & will exhausted with in few decade and rapid growth of population is increasing demand of more energy.

c) Solar energy

22. a) Total R=4+4=8 ohm V=8volt

I=V/R=8/8

=1A

Potential difference across 4ohm=V’=IR

V’=1*4=4V

b) No,There is no difference in ammeter reading of A

1

and A

2 because both are in

Serie.

23. A )

b)1. It drains tissue fluid from the extra cellular space back into blood.

2. it takes lymphocytes and antibodies from the lymph nodes to the blood.

3. Some of the fluid from digestive tract is absorbed in the lymph and store the fluid

Temporarily.

OR

DIAGRAM OF EXCRETORY SYSTEM

B) 1. Transpiration

2. Bark formation

3. Stomata (gas exchange)

24. A) due to presence of strong electrostatic force of attraction between ions

B) This is due to the formation of thin protective oxide layer on the surface of

Aluminum but in case of iron the oxide layer peels off exposing fresh surface to

Corrosion.

C) Because it has low melting point

D) This because oxide can be reduced easily.

E) Because the carbonate layer dissolves in tamarind juice.

OR

A) ZnCO

3 calcination---------- >ZnO + CO

2

B) 2ZnS + 3O2roasting---------- >2ZnO +2 SO

2

C) ZnO + C heating---------- > Zn + CO

D) 2 HgS 3 O

2 heat---------- > 2HgO + 2 SO

2

E) 3 MnO

2

+ 4 Alheat---------- > 3 Mn + 2Al

2

O3

SECTION –B

25. C

26. A (Lemon juice)

27. A (CO

2)

28. A (reddish brown)

29. B (0.1V)

30. A (acidic)

31. A (X)

32. B (5V)

33. C (splitting of water)

34.i) Surface of zinc granules become dull and black . ii) Colourless gas evolves which burns with a pop sound . iii) Reaction mixture becomes hot suggesting the reaction to be exothermic.

35.a) (i) Crackling sound with evolution of brown gas (NO

2

) .

(ii) White coloured lead nitrate changes to light yellow compound (PbO). b) (i) Hissing sound and the solution becomes milky .

(ii) Heat is evolved during the reaction .

36.a) It

should be ensured that the experimental set up is air tight . b)KOHis corrosive .It should be handled carefully.

Paper 7


Time :- 3Hrs.


Class –X Maximum Marks 90

General Instructions: aaa) All questions are compulsory. bbb) The question paper comprises of two sections, A and B. You are to attempt both the sections. ccc) Questions 1 to 3 in section A are one mark questions. These are to be answered in one word or in one sentence. ddd) Questions 4 to 6 in section A are two marks questions. These are to be answered in about

30 words each. eee) Questions 7 to 18 in section A are three marks questions. These are to be answered in about 50 words each. fff) Questions 19 to 24 in section A are five marks questions. These are to be answered in about 70 words each.

Questions 25 to 27 in section B are 2 marks questions and Questions 28 to 36 are multiple choice questions based on practical skills. Each question of multiple choice questions is a one mark question.

You are to select one most appropriate response out of the four provided to you

Section A

Q1. Write the balanced chemical equation for the following reaction:

Sodium + Water  Sodium Hydroxide + Hydrogen

Q2. Name the pigment present in plants which can absorb solar energy.

Q3. Write any two characteristics of good fuel.

Q4. What is the difference between sensory and motor neurons? Which part of the brain maintains posture and equilibrium of the body?

Q5. What is an oxidation reaction? Identify in the following reactions

(i) The substance oxidized

(ii) The substance reduced

Zno + C  Zn + CO

Q6. Write the Namesand chemical formulae of the products formed by heating gypsum at

373 K.

Q7. What is meant by the term magnetic field lines ? List any two properties of magnetic field lines?

Q8.(a) Why cannot a chemical change be normally reversed?

(b) Why is it always essential to balance a chemical equation?

( c) Why does the colour of copper sulphate solution change when an iron nail is dipped in it?

Q9. Crystals of copper sulphateare heated in a test tube for some time.

(a) What is the colour of crystals (i) Before heating (ii) After Heating

(b) What is the source of liquid droplets seen on the inner wall of the test tube during the heating process?

Q10. (a) What are alloys

(b) Name the alloy of aluminium used in making aircraft?

( c)Write the names of metals present in solder?

Q11. (a) Classify the following reactions into different types

(i) AgNo

3

(aq) +Nacl(aq)  AgCl(s)+ NaNo

3

(ii) Cao(s)+H

2

O  Ca(OH)

2

(iii) 2KClO

3

(s)--------> 2KCl + 3O

2

(b)Which of the above reaction(s) is /are participation reaction(s) ?Why is a reaction called precipitation reaction?

Q12. Define the following terms:-

(1). Minerals

(2) Ores

(3) Gangue

Q13. What are the different ways in which glucose is oxidized to provide energy in various organisms?

Q14.Draw human excretory system and label

(1) Left Kidney

(2) Ureter

(3) Urinary bladder

(4) Urethra

Q15. Which animal or plant hormone is associated with the following

1.

Change at puberty in boys

2.

Goitre

3.

Inhibits growth of plants

4.

promotes cell division

5.

Increased sugar level in blood

6.

Dwarfism

Q16. State three advantages of using solar cell to produce electricity. Why is their use for domestic purposes limited?

Q17 (a) What is meant by saying that the potential difference between two points is 1V?

Name a device used to measure potential difference across a conductor.

(b) Electricity Resistivity of two substances at 20 0 C are given below

Silver

Copper

1.60 × 10 -8 Ωm

1.62 × 10 -8 Ωm

Among silver and copper, which one is better conductor ?Why ?

Q18 .State Ohm’s Law? How this law can be verified experimentally?

Q19 (a) State two factors on which the strength of magnetic field due to current carrying conductor depends

(b) Which rule is used to find the direction of magnetic field due to a straight current carrying conductor

Q20. Name the product formed in each case when

(1) Hydrochloric acid reacts with sodium hydroxide(aq)

(2) Cl

2

reacts with slaked lime

(3) Carbon dioxide is passed through lime water

(4) Zinc(s) reacts with Hydrochloric acid(l)

(5) Sodium Bicarbonate (s) is heated

Or

Give reasons for the following

(1) Zinc can displace copper from copper sulphate solution

(2) Silver articles become black after sometime when exposed to air

(3) H

2

gas is not evolved when most metals react with HNO

3

(4) We apply paint on iron grills

(5) We use gold in jewellery

Q21(a) Draw a diagram of nerve cell and label on it following

(1) Nucleus

(2) Dendrites

(b) With the help of schematic diagram trace the events occurring when you step on a sharp object

Or

(a) Name the enzyme present in the saliva? What is its importance

(b) What is emulsification of fats?

(c) Name the substance oxidized in human body during respiration

(d) Why are valves needed in the heart

(e) Why are lungs divided into very small sac like structures

Q22. What are the environmental consequences of the increasing demand of energy ? What steps would you suggest to reduce energy consumption

Or

(a) What ate the limitations of extracting energy from the wind?

(b) What are renewable & non-renewable sources of energy .write two examples of each

Q23(a) Write a short note on

(1) Fuse

(2) Earthing

(b) What is short circuit ?what happens if a domestic circuit is short circuited

Or

A current carrying wire is placed in east west direction. What will be the direction of force experienced by it due to a particular perpendicular magnetic field(external). How will the force will be affected on

(i) Doubling the magnitude of current

(ii) Reversing the direction of current through the wire

Q24(a)What is

(a) The highest (b) The lowest resistance that can be secured by combination of four coils of resistances 4Ω,8 Ω,12 Ω and 24 Ω

(b) An electric lamp of 100 Ω, a toaster of resistance 50 Ω and a water filter of resistance

500 Ω are connected in a parallel to a 220 V source. What is the resistance of an electric iron connected to the same source that takes as much current as all three appliances, and what is the current through it.?

Or

(a) What are the advantages of connecting electrical devices in parallel with the battery instead of connecting them in series

(b) How can three resisto rs of resistances 2 Ω,3 Ω and 6 Ω connected to give a total of (a)

4 Ω (b) 1 Ω

Section B

Multiple Choice questions

Q25. A solution has pH4. The solution will be

(a) Neutral

(b) Acidic

(c) Basic

(d) Ionic

Q26. What will be the pH of a basic solution

(a) pH>7

(b) pH=7

(c) pH < 7

(d) pH=0

Q27.If pH of solution changes from 3 to 4 , the solution becomes

(a) less acidic

(b) Basic

(c) More acidic

(d) Strongly basic

Q28.Which gas is evolved in the reaction of Zinc metal and NaOH

(a) Cl

2

(b) N

2

(c)O

2

(d) H

2

Q29.Name the scientist who proposed acid- Base theory

(a)Arrhenius (c) Dalton

(b) Newton (d) Einstein

Q30.Name the gas evolved when Zinc metal reacts with HCl acid

(a) CO

(b) CO

2

(c) SO

(d)H

Q31. What is the important property of an acid?

2

2

(a) Sour taste

(b) Soapy touch

(c) Bitter Taste

(d) No odour

Q32. A blue litmus paper was first dipped in dil. HCl and then in dil. NaOH solution. Itwas observed that the colour of the litmus paper

(a) Changed to red

(b) Changed first to red and then to blue

(c) Changed blue to colourless

(d) Remained blue in both the solutions

Q33 .Mathematically form of ohm’s law is:

(a) R=1/V

(b) R= V/I

(c) V= I/R

(d) None of above

Q34 A student dips pH paper s in solutions in A and B and observes that the pH paper turns blue and orange respectively in them ?What does he infer .?

Q35.When a (60 Watt and 220 V ) bulb and a 100W and 220 V bulb is connected in series than which bulb will blow brighter

Q36.When asked to set up an experiment to show that light is necessary for photosynthesis a student ran to the school garden to set up the experiment using a plant growing in the school garden the experiment failed ,his fellow student made the following suggestions to get success .

Student a :Safranin should be used instead of iodine.

Student b :The leaf shouid be boiled in alcohol to remove chlorophyll before testing for starch.

Student c :Transparent paper strip should be used instead of black paper strip.

Student d;The plant should be de-strached before starting the experiment .

Which student made the right suggestion ?

MODEL ANSWERS SAMPLE PAPER NO 2(SA-I)

1.2Na+ 2H2O-> 2 NaOH +H2

2.Chlorophyll

3. 1 high calorific value

2.Economic

4. Sensory nerves carry message from muscles to brain , motor nerves to carry message from brain to the muscles .

5. If substance gains oxygen during the reaction.

Oxidation C

Reduction ZnO

6. Plaster of paris, CaSO4.1/2 H2O

7. The field lines which emerges from north and merges at south

(i) They never intersect each other

(ii) They have maximum strength at poles.

8. (a) It cannot be reversed because new substances with new properties are formed.

(b) It is essential to balance the chemical equation to obey law of conservation of mass.

(c) Iron being more reactive than copper displace. So it displace copper from copper sulphate. Blue colour changes to green due to the formation of FeSO4 .

9. (a)(i) Blue (ii)White

(b) loss of water in crystalisation.

10.(a) Homogeneous mixture of two or more metals or non- metals mixed in molten state.

(b) Duralium

(c) solder is an alloy of lead and tin

11. (a) (i) Double displacement

(ii) Combination

(iii) Decomposition

(b) It is a precipitation reaction because precipitates are formed.

12.(i) Materials extracted from ore are called mineral.

(ii) Mineral from which metal is extracted called an ore.

(iii) Impurities present in an ore are called gangue.

13. Glucose (in cytoplasm)- Energy+Pyruvate------ (i) Absence of O2(yeast)->C2H5OH+

CO2+Energy

(ii) Lack of O2(muscle cells)-> Lactic acid + Energy

(iii) Presence of O2(mito.)->CO2+ H2O+

Energy

14.Fig. 6.30 Page no.110 NCERT

15.(i)Testosterone (ii) Thyroxine (iii)Abscissic acid (iv) Cytokinin (v)Insulin(vi) growth hormone

16. (i)Renewable source of energy

(ii) Accessible

(iii) Causes no pollution

(iv)Have no moving parts and requires less maintenance

(b) Availability of Si for making solar cell is limited.

17. 1 volt=1 joule/1 coulomb

Voltmeter

Silver is better conductor since resistivity is less than copper

18. At constant temperature, current flowing through a conductor is directly proportional to potential difference. Fig.12.2 of P.No. 204

19. (i) Number of coils

(ii) nature of materials

Right hand thumb rule

20. 1. NaCl (aq) and water

2. CaOCl2

3CaCO3

ZnCl2 and H2

5 Na2CO3, H2O and CO2

OR

Zn is more reactive than Cu

Tarnishing occurs due to formation of Ag2S

HNO3 is a strong oxidizing agent

To prevent rusting

It is a noble metal

21. Fig 7.1 a P.No. 115

(b) Sharp object-receptor of skin ->sensory nerve-> Spinal cord ->motor nerve->effector muscle in foot

(Reflex arc)

OR

Salivary amylase (digestion of starch)

Breakdown of bigger fat molecules into small globules

Carbohydrates

To prevent backward flow of blood

To increase the surface area

22. (i) Global warming

(ii) Green house effect

(iii) Melting of glaciers

(iv) Chances of flood

Steps to reduce energy-

Alternate source of energy

Economic use of energy.

OR

(a) 1. Wind energy farms can be established where wind blows for greater part of the year.

2 Establishment is costly

3 large area of land is required b. The source of energy which can be renewed easily and are abundance in nature are called renewable source of energy. E.g. wind , air, sunlight.

Those sources of energy which cannot be renewed easily and are limited called non renewablr sources of energy. e.g coal, petroleum.

23. 1. It consists of a piece of wire of alloy having appropriate melting point.

2. transfer of charge from charged body to earth.

3. When the current in the circuit is increased suddenly.

Fuse wire melts and circuit breakdown

OR

The direction of force will be the north direction of wire .

Doubling the magnitude of current , the force acting will be doubled.

The direction of force will be reversed i.e. in the south direction.

24.(a)The highest value of resistance can be secured combining the four coils in series.

(b) The lowest resistance can be secured by combining the four coils in parallel.

(ii) Resistance of electric lamp=100 ohms

Resistance of electric toaster=50 ohm

Resistance of electric filter=500 ohm

Potential difference=220 V

Current flowing through the lamp=V/R=220/100=2.2A

Current flowing through toaster=220/50=4.4A

Current flowing through filter=220/500=0.4A

Total current through the electric iron =2.2+4.4+0.4=7A

Resistance of electric iron=V/I=220/7=31.4 Ohm

OR

Electrical devices are connected in parallel because (i) total resistance dec. when resistances are connected in parallel

(ii) If one appliance is switched off

(iii) Different amount of current flow through each appliance

25. B

26 A

27. A

28. B

29 A

B.Given

R1=2 Ohm

R2=3 Ohm

R3=6 Ohm

When R2 and R3 are connected in parallel R’=1/3+1/6=2+1/6=2 Ohm

R1 and R’ are connected in series 2+2=4 Ohm

When all 3 resistances are connected in parallel 1/R=1/2+1/3+1/6=1 Ohm

30 D

31 A

32 B

33 B

34.He infers that A is sodium carbonate solution and B is acetic acid .

The pH paper turns blue when dipped in solution A . It means A is strong base having pH 9 and the pH paper turns orange when dipped in solution B .it means B is a strong acid having pH 4.

35.The resistance of the bulb is given by R=V2/P.So the resistance of 60W bulb is more than the resistance of 100 w bulb ,when they are connected in series , the current through both bulb s is same.Hence 60 W bulb will be more brighter because P=I2 R

36.Student D made the right suggestion because destarching of the leaf by keeping the plant in darkness before starting the experiment is essential.

Paper 8



Time :- 3Hrs. Class –X Maximum Marks 90

General Instructions: a) All questions are compulsory. b) The question paper comprises of two sections, A and B. You are to attempt both the sections. c) Questions 1 to 3 in section A are one mark questions. These are to be answered in one word or in one sentence. d) Questions 4 to 6 in section A are two marks questions. These are to be answered in about 30 words each. e) Questions 7 to 18 in section A are three marks questions. These are to be answered in about 50 words each. f) Questions 19 to 24 in section A are five marks questions. These are to be answered in about 70 words each.

Questions 25 to 27 in section B are 2 marks questions and Questions 28 to 36 are multiple choice questions based on practical skills. Each question of multiple choice questions is a one mark question.

You are to select one most appropriate response out of the four provided to you

SECTION-A

Q1. Name the substance present in the stinging hairs of nettle leaves. 1

Q2. Give one example of a plant part which is positively hydrotropic as well as positively geotropic. 1

Q3. Why are copper wires used as connecting wires? 1

Q4 . Royal water is prepared by mixing two acids ‘A’ and ‘B’ .Identify ‘A’ and ‘B’. What is the ratio in which these two acids are mixed? 2

Q5. Why is there so much emphasis on changing over from petrol/diesel driven automobiles to CNG-driven vehicles? 2

Q6. Cinnabar is an ore of metal X. It exists in the lower order of the reactivity series. Write down the reaction involved in it for the extraction of X. 2

Q7. Can any source of energy be pollution free? Why or Why not? 3

*Q8 . A solution of a substance ‘X’ is used for white washing.

a) Name the substance ‘X’ and write its formula.

b) Write the reaction of th e substance ‘X’ with water.

(2+1=3)

Q9 . A reddish brown metal ‘X’ when heated in the presence of oxygen forms a black compound ‘Y’ which is basic in nature. When heated with hydrogen gas gives back ‘X’.

Identify ‘X’ and ‘Y’. Write down the reactions involved. 3

Q10 . A student took a pale green substance ‘A’ in a test tube and heated it over the flame of a burner. A brown colored residue ‘B’ was formed along with evolution of two gases with burning smell of sulphur. Identify ‘A’ and ‘B’. Write the chemical reaction involved.

3

*Q11 .A substance ‘X’ is used in the kitchen for making tasty crispy pakoras and is also an ingredient of antacid. Name the substance ‘X’

(i) How does ‘X’ help to make cakes and bread soft and spongy?

(1+1+1=3) ( ii) Is the pH value of solution ‘X’ lesser than or greater than 7.0?

Q12. Write the functions of the following in the digestive process:

(i) Bile.

(ii) Bicarbonates secreted by the duodenal wall.

(iii) Pancreatic amylase. (1+1+1=3)

Q13.How does the plant shoot bends, when the plant is placed in a room having only one open window? Which type of tropic movement is this? 3

Q14. On touching a hot plate, you suddenly withdraw your hand. a) Which category of neurons became active first, b) and which one next? c) What name is given to the microscopic gap between two adjacent neurons?

(1+1+1=3)

Q15. A wire of length L and resistance R is stretched so that its length is doubled. How will its

(a) Resistance change (b) Resistivity change?

Q16. A household uses the following electric appliances:

(2+1=3)

(i)Refrigerator of rating 400 W for ten hours each day.

(ii) Two electric fans of rating 80 W each for twelve hours each day.

(iii) Six electric tubes of rating 18 W each for 6 hours each day.

Calculate the electricity bill of the household for the month of June if the cost per unit of electric energy is Rs. 3.00. 3

Q17.H

2 has been considered as a rocket fuel. Would you consider it as a cleaner fuel than

CNG? Why or Why not?3

Q18.Why is the earth pin thicker and longer than the live and the neutral pins? 3

Q19.i A coil of insulated copper wire is connected to a galvanometer. What would happen if a bar magnet is a) Pushed into the coil? b) Withdrawn from inside the coil? c) Held stationaryinside the coil? ii-State flaming right hand rule .

Q20.Describe with the help of an activity the factors on which the Resistance of a conductor depends. Also write the appropriate formula for it. (4+1=5)

OR

Define and Describe with the help of an activity the Ohm’s law. Also draw the appropriate graph. (4+1=5)

Q21 . a)”Two magnetic lines of force never intersect each other”. Comment.

b) Draw magnetic field lines around a current carrying circular coil. Define Right hand thumb rule. (2+3=5)

OR a) List the properties of magnetic lines of force. b) Draw magnetic field lines through and around a current carrying solenoid coil. What is its use? (2+3=5)

Q22. a) Veins and arteries carry blood. Which of these carry blood i) Away from the heart? ii) Back to the heart? b) Draw a well labeled diagram of human heart.

(2+3=5)

OR a) Why are glomeruli considered as dialysis bags? b) Draw a well labeled diagram of a nephron.

(2+3=5)

Q23. a)Why is sodium kept immersed in kerosene oil? b) Write equations for the reactions of i) Iron with steam. ii) Calcium and potassium with water.

(2+3=5)

OR a) Show the formation of MgO by the transfer of electrons. b) Why do ionic compounds have high melting points?

(2+3=5)

Q24. Compounds such as alcohols and glucose also contain hydrogen but are not categorized as acids.Describe an Activity to prove it. (5)

OR

Five solutions A, B ,C, D and Ewhen tested with universal indicator showed pH as

4,1,11,7 and 9, respectively. Which solution is a) neutral b) Strongly alkaline? c) Strongly acidic? d) Weakly acidic? e) Weaklyalkaline?

Arrange the pH in increasing order of hydrogen- ion concentration.

(5)

Section B

Q25.A student took the following samples to find out their pH using pH paper ,dilute hydrochloric acid , lemon juice,washing soda and soap solution .The teacher remarked that one of the samples , when taken was not proper . To which sample was the teacher referring to ?

Q26.What will happen if a student while studying the dependence of current on the potenitial difference keeps the circuit closed for a long time to measure the current and potential difference .

Q.27.While doing the experiment to show light is necessary for photosynthesis the student was given following substances by his fellow students .which are the correct suggestion given by his fellow students? i.Safranine should be used instead of Iodine . ii.The leaf should be boiled in alcohol with water bath to remove chlorophyll. iii.the transparent paper strip should be used instead of black paper strip . iv .The plant should be destrached before starting the experiment .

Q28) The pH of a solution is 4. It is: i) Basic. ii) Acidic. iii) Neutral. iv) Salty.

Q29) Which of the following will turn red litmus to blue litmus? a) Sulphuric acid b) lemon juice d) hydrochloric acid.

c) sodium hydroxide

Q30)The gas produced on adding sodium carbonate in acids : a) hydrogen b) oxygen c) carbondioxide d) carbonmonoxide

Q231) On adding HCI to Zn metal, the gas produced is: a)hydrogen c)chlorine b) oxygen d) carbondioxide

Q32) Resistance is less when resistors are connected in : a) Series b) parallel c) either series or parallel d) both series or parallel

Q33) in a circuit ammeter is always connected in : a) Series b) parallel c) either series or parallel d) both series or parallel

Q34) The relation between V-I in a conductor is given by: a) Ampere. b) Ohm. c) Coulomb. d) Fleming.

Q35)On mixing the aqueous solutions of sodium sulphate and barium chloride the color of the precipitate formed is: a) Black b) Green. c) Brown d) White.

Q36) The color of metal deposited when iron nails are dipped in aqueous solution of copper sulphateis : a) Reddish brown. b) Grey. b) silvery white. d) Green.

MODEL ANSWERS 4 (SA1)

SCIENCE (X)

Marking Scheme

Section-A

MM: 90

1. Methonoic acid

2. Roots

1

1

3. The Electrical Resistivity of copper is low 1

4. 3HCL : HNO

3

2

5. CNG on burning produces only carbon dioxide and water. It does not produce smoke. It does not leave unburned hydro-carbons, lead particulates etc. 2

6. X is mercury and the ore is HgS.

2HgS(s)+3O

2

(g)---------------------------->2HgO(s)+2SO

2

(g)

2HgO(s)----------------------------->2Hg(l)+O

2

(g) 2

7. No source of energy can be called pollution free, because the use of any source of energy disturbs the environment in one way or the other. The actual source of energy may be pollution free, but the assembly of the device might have caused some damage to the

environment. So, in absolute sense no source of energy can be called pollution free.

2

8. (a) Calcium Oxide CaO

(b) CaO(s) +H

2

O-------------------------->Ca(OH)

2

(aq)

3

Quick lime (slaked lime)

9. Oxygen reacts with copper to form copper oxide which has black colour 3

2Cu(s)+O

2

(g)-------------------> 2CuO(s)

Air Black

CuO+H2----------------->Cu+H

2

O

The copper oxide is losing oxygen and is being reduced. The hydrogen is gaining oxygen and it being oxidized .

10. 2FeSO

4

(s) ------------>Fe

2

O3(s)+SO

2

(g)+SO

3

(g)

A (green) B(brown)

11 2NaHCO

3

------------------------------------->Na

2

CO

3

+H

2

O+CO

2

X(sodium hydrogen carbonate) (Sodium Carbonate)

3

3

(i) When CO

2

gas escapes as bubbles it leaves behind pores which make the cake or bread soft and spongy.

(ii) It is salt of strong base so the pH of the solution will be more than 7.0.

12. (i) Bile- it is secreted by the gall bladder and it emulsifies the fats into the smaller droplets for their easy digestion.

(ii) It provides alkaline medium in the duodenum which is needed for the action of pancreatic enzymes of different food components for their digestion.

(iii) Pancreatic amylase enzymes digests starch and changes it into maltose. 3

13. When a plant is placed in such a room that has only one open window, the shoot of the plant bends towards the direction of light. Plant hormone auxin is formed that diffuses towards the shady side of the shoot and stimulates the cells to live longer on the side of the

shoot which is away from light. In this way the shoot bends towards the light.

3

14. On touching a hot plate, first the sensory neurons are activated, which take the information to the brain or spinal cord. Next, the motor neurons become active and bring the impulses from the brain to the muscles. On receiving these impulses the muscles contract and the hand is immediately removed from the hot plate.

Synapse. 3

15. (a) If the original length of the wire is I and its cross-sectional area is A, then R=pl/A.

When length becomes 21, cross-sectional area reduces to A/2 because volume does not change. The new resistance=p((21)/A/2=4 pl/A=4R

(b) Resistivity does not change. 3

16. Electrical energy consumed per day =400X10+2X80X12+6X18X6

=4000+1920+648

=6568Wh

=6.568 kWh

Electrical energy consumed in 30 days =6.568X30

=197 kWh (units)

Electrical Bill =197X3

=Rs. 591. 3

17. Hydrogen when burned in presence of oxygen produces water as the only product with release of heat and energy. Water does not cause any damage to environment while CNG during burning produces CO

2

and H

2

O. CO

2

is not a pollutant yet it leads to rise in the temperature (global warming), this rise is called greenhouse effect and this will affect polar ice and life on the earth is at risk. Thus hydrogen is cleaner fuel than CNG.

3

18 It is thicker so that it does not enter into the live or neutral sockets. It is made longer so that it gets connected to the earth terminal earlier than the live and neutral pins. This ensures the safety of the user. 3

19.(i) Due to change in magnetic flux linked with coils, the galvanometer shows deflection(say towards right).

(ii) Due to the change in magnetic flux linked with coil, the galvanometer shows deflection

(say towards left opposite to that in case i)

(iii) As it is stationary no change in magnetic flux linked with coil, so galvanometer shows no deflection. leming's right hand rule (for generators ) shows the direction of induced current when a conductor moves in a magnetic field .

The right hand is held with the thumb , first finger and second finger mutually perpendicular to each other (at right angles), as shown in the diagram .

 The Thu m b represents the direction of M otion of the conductor.



The F irst finger represents the direction of the F ield. (north to south)



The Se c ond finger represents the direction of the induced or generated C urrent (the direction of the induced current will be the direction of conventional current; from positive to negative).



One particular way of remembering the rule is the "FBI" acronym for F orce (or otherwise motion), B as the magnetic field sign and I as the current. The subsequent letters correspond to subsequent fingers, counting from the top. Thumb -> F; First finger -> B; Second finger -> I



There is also a Fleming's left hand rule (for electric motors ). The appropriately handed rule can be recalled from the letter " g ", which is in "ri g ht" and " g enerator".

5

20. Activity 12.3 of NCERT Book 5

R=pl/A.

OR

Activity 12.1 of NCERT Book

Figure 12.3 of NCERT Book 5

21.a) No two field lines are found to cross each other. If they did, it would mean that at the point of intersection , the compass needle would point towards two directions, which is not possible.

b) Figure 13.8 of NCERT Book correct definition of rule 5

OR a) Any two properties

(b) Figure 13.10 of NCERT Book

22. a) 1.Arteries carry blood away from the heart.

2. Veins carry blood back to the heart

5

5

(b) Figure 6.10 of NCERT Book

5

OR

(a)The main function performed by the glomeruli is selective filtration . They filter small molecules containing glucose, salt, urea and liquid serum etc. The large molecules such as proteins remain in blood. Thus, glomeruli of the kidneys function as dialysis bags. b) Figure 6.14 of NCERT Book

23. a) Sodium reacts with oxygen at room temperature

(b) correct equations

OR a) Correct formation by dot representation method.

b) Correct explanation.

24. ( a) Activity 3.13 of NCERT Book

(i) D

(ii) C

(iii)

(iv)

B

A

5

5

(v) E

Correct increasing order.

Section B

25. ii

26. c

27. c

28. a

29. b

30. a

31. b

32. d

33. a

34.The teacher was referring to washing soda because it is in powder form not in liquid form

.To find pH using pH paper the sample should be in liquid form .

35.If The circuit is kept closed for a long time t ,resistor will get heated up and its value will change ,this is because heat produced any resistor

H=I2 Rt

As time will increase heat produced will increase .

36.suggestions ii and iv are correct .

Click Here For Notice File - kendriya vidyalaya no.2 akhnoor

B =

tesla

SAMPLE PAPER NO 1 (SA-I)

Subject- Science

Class –X Maximum Marks 90 Time :- 3Hrs.

Section –A

SECTION :-B

is

given out during respiration “ ?

MODEL ANSWERS SAMPLE PAPER NO 1(SA-I)

Section –A

SECTION –B

) .

(ii) White coloured lead nitrate changes to light yellow compound (PbO). b) (i) Hissing sound and the solution becomes milky .

(ii) Heat is evolved during the reaction .

should be ensured that the experimental set up is air tight . b)KOHis corrosive .It should be handled carefully.

SAMPLE PAPER NO 2 (SA-I)

Time :- 3Hrs.

Subject- Science

Class –X Maximum Marks 90

Section A

Section B

Multiple Choice questions

MODEL ANSWERS SAMPLE PAPER NO 2(SA-I)

SAMPLE PAPER NO 4 (SA-I)

Subject- Science

Time :- 3Hrs. Class –X Maximum Marks 90

Section B

Section B

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Click Here For Notice File - kendriya vidyalaya no.2 akhnoor

B =

tesla

SAMPLE PAPER NO 1 (SA-I)

Subject- Science

Class –X Maximum Marks 90 Time :- 3Hrs.

Section –A

SECTION :-B

is

given out during respiration “ ?

MODEL ANSWERS SAMPLE PAPER NO 1(SA-I)

Section –A

SECTION –B

) .

(ii) White coloured lead nitrate changes to light yellow compound (PbO). b) (i) Hissing sound and the solution becomes milky .

(ii) Heat is evolved during the reaction .

should be ensured that the experimental set up is air tight . b)KOHis corrosive .It should be handled carefully.

SAMPLE PAPER NO 2 (SA-I)

Time :- 3Hrs.

Subject- Science

Class –X Maximum Marks 90

Section A

Section B

Multiple Choice questions

MODEL ANSWERS SAMPLE PAPER NO 2(SA-I)

SAMPLE PAPER NO 4 (SA-I)

Subject- Science

Time :- 3Hrs. Class –X Maximum Marks 90

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