Science · Sample Paper 3

General instructions

Section A · Objective

1. Question 11 mark

   The reaction BaCl₂ + Na₂SO₄ → BaSO₄ + 2NaCl is a

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

   Food items fried in oil are flushed with nitrogen in packets to prevent

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

   The pH of human blood is about

   1. A.5.4
   2. B.7.4
   3. C.9.4
   4. D.2.0
4. Question 41 mark

   Which gas is released when zinc reacts with dilute hydrochloric acid?

   1. A.oxygen
   2. B.hydrogen
   3. C.chlorine
   4. D.carbon dioxide
5. Question 51 mark

   Which non-metal is lustrous?

   1. A.sulphur
   2. B.iodine
   3. C.phosphorus
   4. D.carbon (as coal)
6. Question 61 mark

   The process of coating iron with zinc to prevent rusting is

   1. A.electroplating with chromium
   2. B.galvanisation
   3. C.alloying
   4. D.anodising
7. Question 71 mark

   Which of these is an unsaturated hydrocarbon?

   1. A.CH₄
   2. B.C₂H₆
   3. C.C₂H₄
   4. D.C₃H₈
8. Question 81 mark

   The functional group in ethanol is

   1. A.–CHO
   2. B.–OH
   3. C.–COOH
   4. D.–CO–
9. Question 91 mark

   The enzyme in saliva that digests starch is

   1. A.pepsin
   2. B.salivary amylase
   3. C.lipase
   4. D.trypsin
10. Question 101 mark

    Translocation of food in plants takes place through

    1. A.xylem
    2. B.phloem
    3. C.stomata
    4. D.root hairs
11. Question 111 mark

    Which plant hormone inhibits growth and causes wilting of leaves?

    1. A.auxin
    2. B.gibberellin
    3. C.abscisic acid
    4. D.cytokinin
12. Question 121 mark

    The site of fertilisation in human females is the

    1. A.uterus
    2. B.oviduct (fallopian tube)
    3. C.ovary
    4. D.vagina
13. Question 131 mark

    A cross between a tall pea plant (TT) and a dwarf plant (tt) gives offspring that are

    1. A.all dwarf
    2. B.all tall
    3. C.half tall, half dwarf
    4. D.3 tall : 1 dwarf
14. Question 141 mark

    A convex mirror always forms an image that is

    1. A.real and inverted
    2. B.virtual, erect and diminished
    3. C.virtual and magnified
    4. D.real and magnified
15. Question 151 mark

    Two resistors of 6 Ω each are connected in parallel. The equivalent resistance is

    1. A.12 Ω
    2. B.3 Ω
    3. C.6 Ω
    4. D.1.5 Ω
16. Question 161 mark

    Which of these is a non-biodegradable substance?

    1. A.paper
    2. B.fruit peel
    3. C.polythene
    4. D.cotton cloth
17. Question 171 mark

    Assertion (A): Ionic compounds have high melting and boiling points.

    Reason (R): There are strong electrostatic forces between oppositely charged ions.

    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): A ray passing through the optical centre of a lens goes undeviated.

    Reason (R): The two faces of a lens near the optical centre are nearly parallel.

    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): The magnetic field inside a long solenoid is uniform.

    Reason (R): The field lines inside a solenoid are parallel straight lines.

    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): The sex of a child is determined by the father.

    Reason (R): The mother carries two X chromosomes, while the father has one X and one Y.

    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

   Why are decomposition reactions called the opposite of combination reactions? Give one example of each.

2. Question 222 marks

   What is a neutralisation reaction? Give one example from daily life.

3. OR

   Question 222 marks

   Write the chemical name and formula of washing soda. Give one use.

4. Question 232 marks

   Why does carbon form covalent bonds rather than ionic bonds?

5. Question 242 marks

   Why do the walls of the heart's ventricles have thicker muscles than the atria?

6. Question 252 marks

   A concave lens has a focal length of 15 cm. At what distance should an object be placed so that it forms an image 10 cm from the lens?

7. OR

   Question 252 marks

   What is the power of accommodation of the eye?

8. Question 262 marks

   What is biological magnification? Which organisms are most affected?

Section C · Short answer

1. Question 273 marks

   Balance the following and name the type of reaction: (a) Fe + H₂O → Fe₃O₄ + H₂ (b) Pb(NO₃)₂ + KI → PbI₂ + KNO₃ (c) Zn + CuSO₄ → ZnSO₄ + Cu

2. Question 283 marks

   Explain how metals are extracted from their oxides: (a) by heating alone for mercury (b) by reduction with carbon for zinc (c) by electrolysis for sodium.

3. OR

   Question 283 marks

   What is corrosion? Name the green coating on copper and the black coating on silver. Give one method to prevent rusting.

4. Question 293 marks

   What is saponification? Explain how soap removes oily dirt.

5. Question 303 marks

   Describe the role of the following: (a) thyroxine (b) insulin (c) adrenaline.

6. Question 313 marks

   What is pollination? Differentiate between self-pollination and cross-pollination.

7. OR

   Question 313 marks

   What are the advantages of sexual reproduction over asexual reproduction?

8. Question 323 marks

   A wire of resistance 10 Ω is stretched to twice its length. Find its new resistance. What is resistivity, and does it change?

9. Question 333 marks

   What is electromagnetic induction? Describe an activity to demonstrate it.

Section D · Long answer

1. Question 345 marks

   (a) Describe the structure and function of a nephron. (b) How is the amount of urine produced regulated?

2. OR

   Question 345 marks

   (a) Explain the process of nutrition in Amoeba. (b) What are the three steps of photosynthesis?

3. Question 355 marks

   (a) What is hypermetropia? State two causes and how it is corrected, with a description of the ray diagram. (b) Why do we see a rainbow after rain?

4. Question 365 marks

   (a) Derive the expression for the equivalent resistance of three resistors in parallel. (b) Resistors of 3 Ω, 6 Ω and 2 Ω are connected in parallel across a 6 V battery. Find the total current.

5. OR

   Question 365 marks

   (a) Draw (describe) the magnetic field lines around a bar magnet and state their properties. (b) Explain the function of an earth wire and a fuse in domestic circuits.

Section E · Case study

1. Question 374 marks

   Case study — Indicators at home. Neha tested some household substances with turmeric and with red cabbage juice. Turmeric turned red in soap solution and baking soda solution. Red cabbage juice turned red in lemon juice and vinegar, and green in soap solution.

   (i) Which substances in the case are acidic? (1 mark)

   (ii) What does the colour change of turmeric show about soap solution? (1 mark)

   (iii) What are olfactory indicators? Give two examples. (2 marks)

   OR

   (iii) Why does baking soda help when a bee sting causes pain? (2 marks)

2. Question 384 marks

   Case study — Car mirrors. A car has a convex mirror as its side mirror and its headlights use concave reflectors. A driver sees a following vehicle 10 m behind in the side mirror, which has a radius of curvature of 3 m.

   (i) Why is a convex mirror used as a side mirror? (1 mark)

   (ii) What is the focal length of the side mirror? (1 mark)

   (iii) Find the position of the image of the following vehicle. (2 marks)

   OR

   (iii) Why are concave reflectors used in headlights? Where is the bulb placed? (2 marks)

3. Question 394 marks

   Case study — A pond ecosystem. A pond contains algae, small fish (feeding on algae), large fish (feeding on small fish) and kingfishers that eat large fish. Bacteria and fungi live in the mud.

   (i) Write the food chain in the pond. (1 mark)

   (ii) What is the role of bacteria and fungi in the pond? (1 mark)

   (iii) If the algae receive 10 000 J of energy, how much will reach the kingfisher? Explain. (2 marks)

   OR

   (iii) What would happen if all the large fish were removed from the pond? (2 marks)