CBSE Class 10 Science 2020 — Set 4

Questions in this 2020 Science paper (Set 4)

All 30 questions from this set, exactly as asked. Try each one, then open the question-paper PDF above for the complete paper.

1. 1.
   Write the number of valence electrons present in a nitrogen atom (7¹⁴N).
2. 2.
   Define the term induced electric current.
3. 3.
   Answer question numbers 3(a) – 3(d) on the basis of your understanding of the following paragraph and the related studied concepts: Around the year 1800, only 30 elements were known. Dobereiner in 1817 and Newlands in 1866 tried to arrange the then known elements and formed laws which were rejected by the scientists. Even after the rejection of the proposed laws, many scientists continued to…
4. 3 (b).
   Why did Mendeleev leave some gaps in the Periodic table?
5. 3 (c).
   If the letter 'R' was used to represent any of the elements in the group, then the hydride and oxide of carbon would respectively be represented as:

   • (a) RH₄, RO
   • (b) RH₄, RO₂
   • (c) RH₂, SO₃
   • (d) RH₂, RO
6. 3 (d).
   Isotopes are:

   • (a) Atoms of an element with similar chemical properties but different atomic masses.
   • (b) Atoms of different elements with similar chemical properties but different atomic masses.
   • (c) Atoms of an element with different chemical properties but same atomic masses.
   • (d) Atoms of different elements with different chemical properties but same atomic masses.
7. 4.
   Answer question numbers 4(a) – 4(d) on the basis of your understanding of the following paragraph and the related studied concepts: India today is facing the problem of overuse of resources, contamination of water and soil and lack of methods of processing the waste. The time has come for the world to say goodbye to “single-use plastics”. Steps must be undertaken to develop environment-friendly…
8. 4 (b).
   Name any two uses of “single-use plastic” in daily life.
9. 4 (c).
   If we discontinue the use of plastic, how can an environment-friendly substitute be provided?
10. 4 (d).
    Do you think microbes will work similarly in landfill sites as they work in the laboratory? Justify your answer.
11. 5.
    Which one of the following statements is correct about the human circulatory system?

    • (a) Blood transports only oxygen and not carbon dioxide.
    • (b) Human heart has five chambers.
    • (c) Valves ensure that the blood does not flow backwards.
    • (d) Both oxygen-rich and oxygen-deficient blood gets mixed in the heart.
12. 6.
    Anaerobic process:

    • (a) takes place in yeast during fermentation.
    • (b) takes place in the presence of oxygen.
    • (c) produces only energy in the muscles of human beings.
    • (d) produces ethanol, oxygen and energy.
13. 7.
    Fertilisation is the process of:

    • (a) transfer of male gamete to female gamete.
    • (b) fusion of nuclei of male and female gamete.
    • (c) adhesion of male and female reproductive organs.
    • (d) the formation of gametes by a reproductive organ.
14. 8.
    If a person has five resistors each of value 1/5 Ω, then the maximum resistance he can obtain by connecting them is:

    • (a) 1 Ω
    • (b) 5 Ω
    • (c) 10 Ω
    • (d) 25 Ω
15. 9.
    Fleming’s Right-hand rule gives:

    • (a) magnitude of the induced current.
    • (b) magnitude of the magnetic field.
    • (c) direction of the induced current.
    • (d) both, direction and magnitude of the induced current.
16. 10.
    Which one of the following statements is not true about nuclear energy generation in a nuclear reactor?

    • (a) Energy is obtained by a process called nuclear fission.
    • (b) The nucleus of Uranium is bombarded with high energy neutrons.
    • (c) A chain reaction is set in the process.
    • (d) In this process a tremendous amount of energy is released at a controlled rate.
17. 11.
    Food web is constituted by:

    • (a) relationship between the organisms and the environment.
    • (b) relationship between plants and animals.
    • (c) various interlinked food chains in an ecosystem.
    • (d) relationship between animals and environment.
18. 12.
    Choose the incorrect statement from the following:

    • (a) Ozone is a molecule formed by three atoms of oxygen.
    • (b) Ozone shields the surface of the Earth from ultraviolet radiations.
    • (c) Ozone is deadly poisonous.
    • (d) Ozone gets decomposed by UV radiations.
19. 13.
    For question numbers 13 and 14, two statements are given — one labelled as Assertion (A) and the other labelled as Reason (R). Select the correct answer from the codes (a), (b), (c) and (d) as given below: (a) Both (A) and (R) are true and (R) is the correct explanation of the assertion (A). (b) Both (A) and (R) are true, but (R) is not the correct explanation of the assertion (A). (c) (A) is…
20. 14.
    Assertion (A): The sex of a child in human beings will be determined by the type of chromosome he/she inherits from the father. Reason (R): A child who inherits 'X' chromosome from his father would be a girl (XX), while a child who inherits a 'Y' chromosome from the father would be a boy (XY).
21. 15.
    Lead nitrate solution is added to a test tube containing potassium iodide solution.

    • (a) Write the name and colour of the compound precipitated.
    • (b) Write the balanced chemical equation for the reaction involved.
    • (c) Name the type of this reaction justifying your answer.
22. 16.
    List three differentiating features between the processes of galvanisation and alloying. OR Compare in tabular form the reactivities of the following metals with cold and hot water:

    • (a) Sodium
    • (b) Calcium
    • (c) Magnesium
23. 17.
    Carbon, a member of group 14, forms a large number of carbon compounds estimated to be about three million. Why is this property not exhibited by other elements of this group? Explain.
24. 18.
    A cheetah, on seeing a prey, moves towards him at a very high speed. What causes the movement of his muscles? How does the chemistry of cellular components of muscles change during this event?
25. 19.
    Define geotropism. Draw a labelled diagram of a plant showing geotropic movements of its parts.
26. 20.
    Define the term evolution. “Evolution cannot be equated with progress.” Justify this statement. OR “During the course of evolution, organs or features may be adapted for new functions.” Explain this fact, by choosing an appropriate example.
27. 21.
    A concave mirror is used for image formation for different positions of an object. What inferences can be drawn about the following when an object is placed at a distance of 10 cm from the pole of a concave mirror of focal length 15 cm?

    • (a) Position of the image
    • (b) Size of the image
    • (c) Nature of the image Draw a labelled ray diagram to justify your inferences.
28. 22.
    The refractive index of a medium 'x' with respect to a medium 'y' is 2/3 and the refractive index of medium 'y' with respect to medium 'x' is 4/3. Find the refractive index of medium 'y' with respect to medium 'x'. If the speed of light in medium 'x' is 3 × 10⁸ ms⁻¹, calculate the speed of light in medium 'y'.
29. 23.
    A person may suffer from both myopia and hypermetropia defects.

    • (a) What is this condition called?
    • (b) When does it happen?
    • (c) Name the type of lens often required by the persons suffering from this defect. Draw labelled diagram of such lenses.
30. 24.
    How will you use two identical glass prisms so that a narrow beam of white light incident on one prism emerges out of the second prism as white light? Draw and label the ray diagram.
31. 25.
    A cloth strip dipped in onion juice is used for testing a liquid 'X'. The liquid 'X' changes its odour. Which type of an indicator is onion juice? The liquid 'X' turns blue litmus red. List the observations the liquid 'X' will show on reacting with the following:

    • (a) Zinc granules
    • (b) Solid sodium carbonate Write the chemical equations for the reactions involved. OR Define water of…
32. 26.
    • (i) Write two properties of gold which make it the most suitable metal for ornaments.
    • (ii) Name two metals which are the best conductors of heat.
    • (iii) Name two metals which melt when you keep them on your palm.
    • (b) Explain the formation of ionic compound CaO with electron-dot structure. Atomic numbers of calcium and oxygen are 20 and 8 respectively.
33. 27.
    Why is nutrition necessary for the human body? (b) What causes movement of food inside the alimentary canal? (c) Why is small intestine in herbivores longer than in carnivores? (d) What will happen if mucus is not secreted by the gastric glands?
34. 28.
    Draw a neat diagram showing fertilisation in a flower and label

    • (a) Pollen tube,
    • (b) Male germ cell and
    • (c) Female germ cell, on it. Explain the process of fertilisation in a flower. What happens to the
    • (i) ovary and
    • (ii) ovule after fertilisation? OR
    • (a) What is puberty?
    • (b) Describe in brief the functions of the following parts in the human male reproductive system:
    • (i) Testes
    • (ii) Seminal…
35. 29.
    Draw a schematic diagram of a circuit consisting of a battery of 3 cells of 2 V each, a combination of three resistors of 10 Ω, 20 Ω and 30 Ω connected in parallel, a plug key and an ammeter, all connected in series. Use this circuit to find the value of the following:

    • (a) Current through each resistor
    • (b) Total current in the circuit
    • (c) Total effective resistance of the circuit OR Two…
36. 30.
    State Fleming’s Left-hand rule. (b) List three characteristic features of the electric current used in our homes. (c) What is a fuse? Why is it called a safety device? (d) Why is it necessary to earth metallic electric appliances?

Class 10 Science exam pattern (80 marks)

The theory paper carries 80 marks over 3 hours (39 questions, with internal choice in some). Section-wise structure:

Structure per the CBSE 2023-24 sample-paper design; question wording varies by set.

Prepare with

How to use these papers

1. 1Start chapter-wise early in the year — solve only the Science questions from a chapter you have just finished.
2. 2Switch to full timed papers 2–3 months before the exam: one complete set in the real time limit, no notes.
3. 3Self-mark against the marking scheme, then fix every mistake with our free NCERT solutions.
4. 4Re-attempt your weakest chapters until the recurring question types feel routine.

CBSE Class 10 Science 2020 paper — FAQ