Science · Sample Paper 2

General instructions

Section A · Objective

1. Question 11 mark

   The reaction CaCO₃ → CaO + CO₂ on heating is a

   1. A.combination reaction
   2. B.thermal decomposition reaction
   3. C.displacement reaction
   4. D.double displacement reaction
2. Question 21 mark

   The brown coating that forms on iron left in moist air is an example of

   1. A.rancidity
   2. B.corrosion
   3. C.neutralisation
   4. D.sublimation
3. Question 31 mark

   Which of the following turns red litmus blue?

   1. A.Lemon juice
   2. B.Vinegar
   3. C.Soap solution
   4. D.Hydrochloric acid
4. Question 41 mark

   The chemical formula of plaster of Paris is

   1. A.CaSO₄·2H₂O
   2. B.CaSO₄·½H₂O
   3. C.CaCO₃
   4. D.CaOCl₂
5. Question 51 mark

   Which of the following metals is liquid at room temperature?

   1. A.Sodium
   2. B.Mercury
   3. C.Gallium
   4. D.Aluminium
6. Question 61 mark

   An alloy of copper and zinc is

   1. A.bronze
   2. B.brass
   3. C.solder
   4. D.steel
7. Question 71 mark

   The number of covalent bonds in a molecule of methane (CH₄) is

   1. A.2
   2. B.3
   3. C.4
   4. D.5
8. Question 81 mark

   The IUPAC name of CH₃CHO is

   1. A.methanal
   2. B.ethanal
   3. C.ethanol
   4. D.ethanoic acid
9. Question 91 mark

   The opening and closing of stomata is controlled by

   1. A.guard cells
   2. B.root hairs
   3. C.xylem
   4. D.phloem
10. Question 101 mark

    The functional unit of the human kidney is the

    1. A.neuron
    2. B.nephron
    3. C.alveolus
    4. D.villus
11. Question 111 mark

    Which part of the brain maintains posture and balance?

    1. A.Cerebrum
    2. B.Cerebellum
    3. C.Medulla
    4. D.Hypothalamus
12. Question 121 mark

    Which of the following reproduces by budding?

    1. A.Amoeba
    2. B.Hydra
    3. C.Planaria
    4. D.Spirogyra
13. Question 131 mark

    A human child inherits an X chromosome from the father. The child will be

    1. A.a boy
    2. B.a girl
    3. C.either
    4. D.cannot be predicted
14. Question 141 mark

    The power of a convex lens of focal length 50 cm is

    1. A.+2 D
    2. B.−2 D
    3. C.+0.5 D
    4. D.+50 D
15. Question 151 mark

    1 volt is equal to

    1. A.1 J/C
    2. B.1 C/J
    3. C.1 J·C
    4. D.1 A/s
16. Question 161 mark

    In a food chain, the organisms that make their own food are called

    1. A.consumers
    2. B.decomposers
    3. C.producers
    4. D.carnivores
17. Question 171 mark

    Assertion (A): Acids should be added to water slowly with constant stirring, not water to acid.

    Reason (R): The dilution of a concentrated acid is highly exothermic.

    1. A.Both Assertion (A) and Reason (R) are true, and R is the correct explanation of A.
    2. B.Both Assertion (A) and Reason (R) are true, but R is not the correct explanation of A.
    3. C.Assertion (A) is true, but Reason (R) is false.
    4. D.Assertion (A) is false, but Reason (R) is true.
18. Question 181 mark

    Assertion (A): Stars twinkle at night.

    Reason (R): Light from stars undergoes continuous atmospheric refraction as the density of air layers keeps changing.

    1. A.Both Assertion (A) and Reason (R) are true, and R is the correct explanation of A.
    2. B.Both Assertion (A) and Reason (R) are true, but R is not the correct explanation of A.
    3. C.Assertion (A) is true, but Reason (R) is false.
    4. D.Assertion (A) is false, but Reason (R) is true.
19. Question 191 mark

    Assertion (A): In household wiring, appliances are connected in parallel.

    Reason (R): In a parallel circuit, each appliance gets the full supply voltage and can be switched on or off independently.

    1. A.Both Assertion (A) and Reason (R) are true, and R is the correct explanation of A.
    2. B.Both Assertion (A) and Reason (R) are true, but R is not the correct explanation of A.
    3. C.Assertion (A) is true, but Reason (R) is false.
    4. D.Assertion (A) is false, but Reason (R) is true.
20. Question 201 mark

    Assertion (A): Arteries have thick, elastic walls.

    Reason (R): Arteries carry blood at low pressure towards the heart.

    1. A.Both Assertion (A) and Reason (R) are true, and R is the correct explanation of A.
    2. B.Both Assertion (A) and Reason (R) are true, but R is not the correct explanation of A.
    3. C.Assertion (A) is true, but Reason (R) is false.
    4. D.Assertion (A) is false, but Reason (R) is true.

Section B · Very short answer

1. Question 212 marks

   What is a redox reaction? Identify the substance oxidised and the substance reduced in: CuO + H₂ → Cu + H₂O.

2. Question 222 marks

   Why does tooth decay start when the pH of the mouth falls below 5.5? How can it be prevented?

3. OR

   Question 222 marks

   Write the chemical name and formula of bleaching powder and give one use.

4. Question 232 marks

   Why do ionic compounds have high melting points? Why do they conduct electricity in molten state?

5. Question 242 marks

   Write the equation for photosynthesis and name two raw materials needed for it.

6. Question 252 marks

   The refractive index of glass is 1.5. What is the speed of light in glass? (Speed of light in vacuum = 3 × 10⁸ m/s)

7. OR

   Question 252 marks

   What is the far point and near point of a normal human eye?

8. Question 262 marks

   Why is only about 10% of energy transferred from one trophic level to the next?

Section C · Short answer

1. Question 273 marks

   What happens when (a) silver chloride is kept in sunlight (b) lead nitrate is heated? Write balanced equations and name the type of reaction.

2. Question 283 marks

   Explain the reactivity series with an example. Why can zinc displace copper from copper sulphate solution but copper cannot displace zinc from zinc sulphate?

3. OR

   Question 283 marks

   Give reasons: (a) Aluminium is a highly reactive metal, yet it is used to make cooking utensils. (b) Carbonate and sulphide ores are usually converted into oxides. (c) Copper vessels develop a green coating in air.

4. Question 293 marks

   What is esterification? Write the equation for the reaction of ethanol with ethanoic acid and state one use of esters.

5. Question 303 marks

   What are tropic movements? Explain phototropism and geotropism with one example each.

6. Question 313 marks

   What is vegetative propagation? Give two advantages and two examples.

7. OR

   Question 313 marks

   List three methods of contraception and state one advantage of each.

8. Question 323 marks

   What is the dispersion of white light? Why do different colours bend through different angles in a glass prism?

9. Question 333 marks

   Describe the pattern of magnetic field lines around a straight current-carrying conductor. How does the field change if the current is increased?

Section D · Long answer

1. Question 345 marks

   (a) Describe the process of digestion of food in the human small intestine. (b) How is the small intestine designed to absorb digested food?

2. OR

   Question 345 marks

   (a) Describe the mechanism of breathing in human beings. (b) How are the lungs designed to maximise gas exchange?

3. Question 355 marks

   (a) An object is placed 15 cm in front of a concave mirror of focal length 10 cm. Find the position, nature and magnification of the image. (b) State two uses of concave mirrors.

4. Question 365 marks

   (a) Derive the expression for the equivalent resistance of three resistors connected in series. (b) Two resistors of 10 Ω and 15 Ω are connected in series with a 5 V battery. Find the current and the potential difference across each resistor.

5. OR

   Question 365 marks

   (a) State Joule's law of heating. (b) An electric iron of 1100 W is used for 2 hours daily. Find the current drawn at 220 V, its resistance, and the energy consumed in 30 days in kWh.

Section E · Case study

1. Question 374 marks

   Case study — Seed colour in peas. Mendel crossed pea plants with round seeds (RR) and wrinkled seeds (rr). All F₁ plants had round seeds. When the F₁ plants were self-pollinated, the F₂ generation had 5,474 round and 1,850 wrinkled seeds.

   (i) Which trait is dominant? (1 mark)

   (ii) What is the genotype of the F₁ plants? (1 mark)

   (iii) Show the F₂ cross and give the genotypic ratio. (2 marks)

   OR

   (iii) Approximately what ratio of round to wrinkled seeds was obtained in F₂, and what does it show? (2 marks)

2. Question 384 marks

   Case study — Safety at home. Domestic circuits in India receive AC at 220 V and 50 Hz. Each circuit has a live wire, a neutral wire and an earth wire. A fuse is connected in the live wire. Appliances with metal bodies are connected to the earth wire.

   (i) What is the colour of the insulation of the earth wire? (1 mark)

   (ii) Why is a fuse connected in the live wire? (1 mark)

   (iii) What is short-circuiting, and how does a fuse protect the circuit? (2 marks)

   OR

   (iii) Why is earthing of metallic appliances necessary? (2 marks)

3. Question 394 marks

   Case study — The ozone hole. Ozone (O₃) in the upper atmosphere shields the Earth from harmful ultraviolet radiation. In the 1980s, scientists found that the amount of ozone was falling sharply, especially over Antarctica. This was traced to synthetic chemicals like chlorofluorocarbons (CFCs), used in refrigerators and aerosol sprays. In 1987, countries signed an agreement to phase out CFCs.

   (i) How is ozone formed in the upper atmosphere? (1 mark)

   (ii) Name the chemicals mainly responsible for ozone depletion. (1 mark)

   (iii) What harm can UV radiation cause to humans? Give two effects. (2 marks)

   OR

   (iii) Suggest two steps an individual can take to reduce damage to the ozone layer. (2 marks)