CBSE Class 10 Science 2020 — Set 3

Questions in this 2020 Science paper (Set 3)

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.
   How are covalent bonds formed?
2. 2.
   Define electropositivity.
3. 3 (a).
   (Based on the passage about Tehri Dam) The Tehri Dam is the highest dam in India and one of the highest in the World. The Tehri Dam withholds a reservoir of capacity 4.0 km³ and surface area 52 km². It is used for irrigation, municipal water supply and the generation of 1000 MW of hydro electricity. The Tehri Dam has been the object of protests. Environment activist Shri Sunder Lal Bahuguna led…
4. 3 (b).
   (Based on Tehri Dam passage) (b) Define 1 MW.
5. 3 (c).
   (Based on Tehri Dam passage) (c) Mention two disadvantages of constructing Tehri Dam.
6. 3 (d).
   (Based on Tehri Dam passage) (d) What happens when water from great heights is made to fall on blades of turbine?
7. 4 (a).
   (Based on passage about TSH levels in women) Thyroid Stimulating Hormone (TSH) levels in women are based on the table given below: Age Range — Normal (mU/L) — Low (mU/L): 18–29 years: 0.4–2.34 mU/L (Normal), < 0.4 mU/L (Low) 30–49 years: 0.4–4.0 mU/L (Normal), < 0.4 mU/L (Low) 50–79 years: 0.46–4.68 mU/L (Normal), < 0.46 mU/L (Low) Women are at greater risk for developing abnormal TSH levels…
8. 4 (b).
   (Based on TSH passage) (b) When do women face a greater risk of abnormal TSH level?
9. 4 (c).
   (Based on TSH passage) (c) State the consequences of low TSH level.
10. 4 (d).
    (Based on TSH passage) (d) Name the mineral that is responsible for synthesis of hormone secreted by thyroid gland.
11. 5.
    The sky appears dark to passengers flying at very high altitudes mainly because:

    • (a) Scattering of light is not enough at such heights.
    • (b) There is no atmosphere at great heights.
    • (c) The size of molecules is smaller than the wavelength of visible light.
    • (d) The light gets scattered towards the earth.
12. 6.
    A cylindrical conductor of length 'l' and uniform area of cross section 'A' has resistance 'R'. The area of cross section of another conductor of same material and same resistance but of length '2l' is:

    • (a) A/2
    • (b) A/2
    • (c) 3A
    • (d) 3A
13. 7.
    The maximum resistance which can be made using four resistors each of resistance 1/2 Ω is:

    • (a) 2 Ω
    • (b) 1 Ω
    • (c) 2.5 Ω
    • (d) 8 Ω
14. 8.
    A diagram of traditional water harvesting system is given below (showing components A, B, and C with a sloped terrain, a wall structure, and a well): The statement which defines the system and its parts is:

    • (a) This is an ideal setting of the Khadin system and A = Catchment area; B = Saline area & C = Shallow dugwell
    • (b) This is an ideal setting of the Shallow dugwell system and A = Catchment…
15. 9.
    Several factories were pouring their wastes in rivers A and B. Water samples were collected from these two rivers. It was observed that sample collected from river A was acidic while that of river B was basic. The factories located near A and B are:

    • (a) Soaps and detergents factories near A and alcohol distillery near B
    • (b) Soaps and detergents factories near B and alcohol distillery near A (c)…
16. 10.
    In which of the following, the identity of initial substance remains unchanged?

    • (a) Curdling of milk
    • (b) Formation of crystals by process of crystallisation
    • (c) Fermentation of grapes
    • (d) Digestion of food
17. 11.
    An aqueous solution 'A' turns phenolphthalein solution pink. On addition of an aqueous solution 'B' to 'A', the pink colour disappears. The following statement is true for solutions 'A' and 'B':

    • (a) A is a strong base and B is a weak base.
    • (b) A is a strongly acidic and B is a weak acid.
    • (c) A has pH greater than 7 and B has pH less than 7.
    • (d) A has pH less than 7 and B has pH greater than 7.
18. 12.
    An element 'X' is forming an acidic oxide. Its position in modern periodic table will be:

    • (a) Group 1 and Period 3
    • (b) Group 2 and Period 3
    • (c) Group 13 and Period 3
    • (d) Group 16 and Period 3
19. 13.
    Assertion (A): CH₃OH, CH₃CH₂OH and CH₃CH₂CH₂OH are members of a homologous series. Reason (R): A series of compounds with same functional group but differing by –CH₂– unit is called a homologous series.

    • (a) Both (A) and (R) are true and (R) is correct explanation of the assertion.
    • (b) Both (A) and (R) are true but (R) is not the correct explanation of the assertion.
    • (c) (A) is true but (R) is…
20. 14.
    Assertion (A): Alloys are commonly used in electrical heating devices like electric iron and heater. Reason (R): Resistivity of an alloy is generally higher than that of its constituent metals but the alloys have low melting points than their constituent metals.

    • (a) Both (A) and (R) are true and (R) is correct explanation of the assertion.
    • (b) Both (A) and (R) are true but (R) is not the correct…
21. 15.
    Mention with reason the colour changes observed when:

    • (i) silver chloride is exposed to sunlight.
    • (ii) copper powder is strongly heated in the presence of oxygen.
    • (iii) a piece of zinc is dropped in copper sulphate solution.
22. 16.
    Complete and balance the following chemical equations:

    • (i) NaOH(aq) + Zn(s) →
    • (ii) CaCO₃(s) + H₂O(l) + CO₂(g) →
    • (iii) HCl(aq) + H₂O(l) →
23. 17.
    Study the data of the following three categories A, B and C. Category A: Li (7), Na (23), K (39) Category B: N (14), P (31), As (74) Category C: B (10.8), Al (27), Ga (69.7)

    • (i) From the given three categories A, B and C, pick the one which forms Dobereiner's Triads.
    • (ii) Why did Mendeleev placed elements of category A, B and C in three different groups?
    • (iii) Is Newland law of octaves…
24. 18 (a).
    From the following group of organisms create a food chain which is the most advantageous for Human beings in terms of energy. Hawk, Rat, Cereal plant, Goat, Snake, Human Being (b) State the possible disadvantage if the cereal plant is growing in soil rich in pesticides. (c) Construct a food web using the organisms mentioned above.
25. 19.
    State the role played by the following in the process of digestion.

    • (i) Enzyme trypsin
    • (ii) Enzyme lipase
    • (b) List two functions of finger like projections present in the small intestine.
26. 20.
    Classify the following as homologous or analogous pairs:

    • (i) Broccoli and Cabbage
    • (ii) Ginger and Radish
    • (iii) Fore limbs of birds and lizard
    • (iv) Wings of a bat and Wings of a bird
    • (b) State the main feature that categorises a given pair of organs as homologous or analogous.
27. 21.
    A green stemmed rose plant denoted by GG and a brown stemmed rose plant denoted by gg are allowed to undergo a cross with each other.

    • (a) List your observations regarding:
    • (i) Colour of stems in their F₁ progeny
    • (ii) Percentage of brown stemmed plants in F₂ progeny if F₁ plants are self pollinated.
    • (iii) Ratio of GG and Gg in the F₂ progeny.
    • (b) Based on the findings of this cross, what…
28. 22.
    The diagram given below shows an object O and its image I. (Diagram shows a lens with object O on one side and image I on the other, with markings at 2F, F on both sides) Without actually drawing the ray diagram, state the following:

    • (i) Type of lens (Converging / Diverging)
    • (ii) Name two optical instruments where such an image is obtained.
    • (iii) List three characteristics of the image formed if…
29. 23.
    Give reasons for the following:

    • (i) There is either a convergence or a divergence of magnetic field lines near the ends of a current carrying straight solenoid.
    • (ii) The current carrying solenoid when suspended freely rests along a particular direction.
    • (iii) The burnt out fuse should be replaced by another fuse of identical rating.
30. 24.
    With the help of labelled ray diagram show the path followed by a narrow beam of monochromatic light when it passes through a glass prism. (b) What would happen if this beam is replaced by a narrow beam of white light?
31. 25.
    Write balanced chemical equations to explain what happens, when:

    • (i) Mercuric oxide is heated.
    • (ii) Mixture of cuprous oxide and cuprous sulphide is heated.
    • (iii) Aluminium is roasted with manganese dioxide.
    • (iv) Ferric oxide is reduced with aluminium.
    • (v) Zinc carbonate undergoes calcination.
32. 26.
    Compare soaps and detergents on the basis of their composition and cleansing action in hard water. (b) What happens when ethanol is treated with sodium metal? State the behaviour of ethanol in this reaction. (c) Draw the structure of cyclohexane. (d) Name the following compound: H—C—C—H with H atoms attached and a double bond (C₂H₂ / Ethyne structure shown as H─C≡C─H)
33. 27.
    Write the correct sequence of steps followed during journey of oxygen rich blood from lungs to various organs of human body. (b) What happens when the system of blood vessels develop a leak?
34. 28.
    Draw a diagram showing germination of pollen on stigma and mark on it the following organs/parts:

    • (i) Pollen Grain
    • (ii) Pollen tube
    • (iii) Stigma
    • (iv) Female germ cell
    • (b) State the significance of pollen tube.
    • (c) Name the parts of flower that develop after fertilization into:
    • (i) Seed
    • (ii) Fruit
35. 29.
    For the combination of resistors shown in the following figure, find the equivalent resistance between M and N. (The figure shows resistors R₁, R₂, R₃ with R₁ in series and R₂, R₃ in parallel between points M and N) (b) State Joule's law of heating. (c) Why we need a 5 A fuse for an electric iron which consumes 1 kW power at 220 V? (d) Why is it impracticable to connect an electric bulb and an…
36. 30 (a).
    A security mirror used in a big showroom has radius of curvature 5 m. If a customer is standing at a distance of 20 m from the cash counter, find the position, nature and size of the image formed in the security mirror. (b) Neha visited a dentist in his clinic. She observed that the dentist was holding an instrument fitted with a mirror. State the nature of this mirror and reason for its use in…

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