Science · Sample Paper 3

General instructions

Section A · Objective

1. Question 11 mark

   Which of these has the strongest forces of attraction between particles?

   1. A.oxygen
   2. B.water
   3. C.iron
   4. D.petrol
2. Question 21 mark

   Dry ice is solid

   1. A.water
   2. B.carbon dioxide
   3. C.nitrogen
   4. D.ammonia
3. Question 31 mark

   Which of these is a suspension?

   1. A.milk
   2. B.chalk powder in water
   3. C.salt solution
   4. D.air
4. Question 41 mark

   Cream is separated from milk by

   1. A.filtration
   2. B.centrifugation
   3. C.sublimation
   4. D.chromatography
5. Question 51 mark

   The symbol of potassium is

   1. A.P
   2. B.Po
   3. C.K
   4. D.Pt
6. Question 61 mark

   The number of atoms in 2 moles of oxygen molecules (O₂) is

   1. A.6.022 × 10²³
   2. B.1.2044 × 10²⁴
   3. C.2.4088 × 10²⁴
   4. D.3.011 × 10²³
7. Question 71 mark

   Protons were discovered by

   1. A.J.J. Thomson
   2. B.E. Goldstein
   3. C.James Chadwick
   4. D.Niels Bohr
8. Question 81 mark

   Atoms of different elements with the same mass number are called

   1. A.isotopes
   2. B.isobars
   3. C.isotones
   4. D.ions
9. Question 91 mark

   The organelle that packages and dispatches materials in the cell is the

   1. A.ribosome
   2. B.Golgi apparatus
   3. C.nucleolus
   4. D.mitochondrion
10. Question 101 mark

    A cell placed in a hypertonic solution will

    1. A.swell
    2. B.shrink
    3. C.burst
    4. D.stay the same
11. Question 111 mark

    Which tissue forms the outer layer of our skin?

    1. A.muscular
    2. B.squamous epithelium
    3. C.nervous
    4. D.areolar
12. Question 121 mark

    The area under a velocity–time graph gives

    1. A.acceleration
    2. B.displacement
    3. C.speed
    4. D.force
13. Question 131 mark

    A force of 20 N acts on a body of mass 4 kg. Its acceleration is

    1. A.80 m/s²
    2. B.5 m/s²
    3. C.0.2 m/s²
    4. D.24 m/s²
14. Question 141 mark

    The SI unit of pressure is

    1. A.newton
    2. B.pascal
    3. C.joule
    4. D.watt
15. Question 151 mark

    An object of mass 1 kg is raised 5 m. Its gain in potential energy is (g = 10 m/s²)

    1. A.5 J
    2. B.50 J
    3. C.500 J
    4. D.0.5 J
16. Question 161 mark

    The loudness of sound depends on its

    1. A.frequency
    2. B.amplitude
    3. C.speed
    4. D.wavelength
17. Question 171 mark

    Assertion (A): We can smell hot food from a distance more quickly than cold food.

    Reason (R): The rate of diffusion of gases increases with temperature.

    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): Neutrons do not affect the chemical properties of an atom.

    Reason (R): Chemical properties depend on the number of electrons in the outermost shell.

    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): A rocket moves forward by pushing exhaust gases backward.

    Reason (R): Action and reaction act on the same body.

    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): Crop rotation helps maintain soil fertility.

    Reason (R): Growing leguminous crops in rotation adds nitrogen to the soil.

    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 does a desert cooler cool better on a hot, dry day?

2. Question 222 marks

   Classify as physical or chemical change: (a) cutting of trees (b) burning of paper (c) melting of butter (d) rusting of iron.

3. OR

   Question 222 marks

   What is a saturated solution? How can an unsaturated solution be made saturated?

4. Question 232 marks

   Calculate the number of moles in 12.044 × 10²³ molecules of water.

5. Question 242 marks

   Differentiate between xylem and phloem (two points).

6. Question 252 marks

   A car travels 30 km at 60 km/h and the next 30 km at 30 km/h. Find its average speed.

7. OR

   Question 252 marks

   Why is it easier to walk on sand with flat shoes than with high heels?

8. Question 262 marks

   Name two exotic breeds of cattle used for higher milk yield and one Indian breed.

Section C · Short answer

1. Question 273 marks

   How would you separate a mixture of (a) alcohol and water (b) iodine and salt (c) oil and water?

2. Question 283 marks

   Give Bohr's model of the atom. Draw (describe) the electron distribution of a sodium atom (atomic number 11).

3. Question 293 marks

   What is plasmolysis? Describe an activity to show it.

4. OR

   Question 293 marks

   Write three differences between prokaryotic and eukaryotic cells.

5. Question 303 marks

   A 1000 kg car moving at 20 m/s is stopped by applying brakes in 4 s. Find (a) the retardation (b) the braking force (c) the distance moved.

6. Question 313 marks

   State Archimedes' principle. Give two applications.

7. Question 323 marks

   Explain how sound travels through air as compressions and rarefactions.

8. OR

   Question 323 marks

   A person stands 85 m from a wall and claps. If the speed of sound is 340 m/s, after how long is the echo heard? What is the minimum distance needed for an echo?

9. Question 333 marks

   What are the factors for which crop varieties are improved? Give three.

Section D · Long answer

1. Question 345 marks

   (a) State the law of constant proportions with an example. (b) Calculate the molecular masses of (i) NH₃ (ii) CaCO₃ (iii) C₂H₅OH. (N = 14, H = 1, Ca = 40, C = 12, O = 16)

2. Question 355 marks

   (a) Derive the equation s = ut + ½at² graphically. (b) A ball rolls down a slope from rest with acceleration 2 m/s². How far does it go in 5 s, and what is its speed then?

3. OR

   Question 355 marks

   (a) State the law of conservation of energy. Show that the total mechanical energy of a freely falling body is conserved. (b) A 2 kg ball is dropped from 20 m. Find its kinetic energy halfway down.

4. Question 365 marks

   (a) Describe the structure of a neuron with a labelled (described) diagram. (b) Name the three types of muscle tissue and state where each is found.

Section E · Case study

1. Question 374 marks

   Case study — Melting ice. In an experiment, students heat crushed ice in a beaker and record the temperature every minute. The temperature stays at 0 °C for several minutes while the ice melts, then rises steadily until it reaches 100 °C, where it stays constant again while the water boils.

   (i) What is the melting point of ice on the Kelvin scale? (1 mark)

   (ii) Why does the temperature stay constant while ice melts? (1 mark)

   (iii) What is latent heat of vaporisation? Why do steam burns hurt more than burns from boiling water? (2 marks)

   OR

   (iii) How would adding salt to the ice change its melting point? Give one use of this. (2 marks)

2. Question 384 marks

   Case study — Weighing on the Moon. An astronaut of mass 70 kg lands on the Moon, where g is about one-sixth of its value on Earth. On Earth, take g = 9.8 m/s².

   (i) What is the astronaut's mass on the Moon? (1 mark)

   (ii) What is the astronaut's weight on Earth? (1 mark)

   (iii) What is the astronaut's weight on the Moon, and why is it less? (2 marks)

   OR

   (iii) Why can the astronaut jump higher on the Moon? (2 marks)

3. Question 394 marks

   Case study — Fish farming. A cooperative in Andhra Pradesh runs fish ponds and also cultures prawns in brackish water near the coast. To increase yield they use composite fish culture, but they face difficulty getting good-quality seed (fry) because some fish breed only in the monsoon.

   (i) What is the difference between capture fishing and culture fishery? (1 mark)

   (ii) Name one marine fish of high economic value. (1 mark)

   (iii) How has the problem of fish seed been solved? (2 marks)

   OR

   (iii) Name two methods to locate large schools of fish in the open sea. (2 marks)