#### Book back Important 4 Marks Questions

10th Standard

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Science

Time : 02:30:00 Hrs
Total Marks : 248

Part A

62 x 4 = 248
1. Two bodies have a mass ratio of 3:4 The force applied on the bigger mass produces an acceleration of 12 ms-2. What could be the acceleration of the other body, if the same force acts on it.

2. A ball of mass 1 kg moving with a speed of 10 ms-1 rebounds after a perfect elastic collision with the floor. Calculate the change in linear momentum of the ball.

3. A mechanic unscrew a nut by applying a force of 140 N with a spanner of length 40 cm. What should be the length of the spanner if a force of 40 N is applied to unscrew the same nut?

4. Find the final temperature of a copper rod. Whose area of cross section changes from 10 m2 to 11 m2 due to heating. The copper rod is initially kept at 90 K. (Coefficient of superficial expansion is 0.0021 /K)

5. Calculate the coefficient of cubical expansion of a zinc bar. Whose volume is increased 0.25 m3 from 0.3 m3 due to the change in its temperature of 50 K.

6. Define electric potential and potential difference.

7. State Ohm’s law.

8. Distinguish between the resistivity and conductivity of a conductor.

9. Air temperature in the Rajasthan desert can reach 46°C. What is the velocity of sound in air at that temperature? (V0 = 331 m s–1)

10. Mention two cases in which there is no Doppler effect in sound?

11. A man is standing between two vertical walls 680 m apart. He claps his hands and hears two distinct echoes after 0.9 seconds and 1.1 second respectively. What is the speed of sound in the air?

12. 88Ra226 experiences three $\alpha$ - decay. Find the number of neutrons in the daughter element.

13. In Japan, some of the new born children are having congenital diseases. Why?

14. Give any two uses of radio isotopes in the field of agriculture?

15. Calculate the number of moles in
(i) 27g of Al
(ii) 1.51 × 1023 molecules of NH4Cl

16. Give the salient features of “Modern atomic theory”.

17. Calculate the % of oxygen in Al2(SO4)3. (Atomic mass: Al-2, O-16, S -32).

18. a) State the reason for addition of caustic alkali to bauxite ore during purification of bauxite.
b) Along with cryolite and alumina, another substance is added to the electrolyte mixture. Name the substance and give one reason for the addition

19. The electronic configuration of metal A is 2,8,18,1.
The metal A when exposed to air and moisture forms B a green layered compound. A with con. H2SO4 forms C and D along with water. D is a gaseous compound. Find A,B,C and D.

20. Explain smelting process.

21. Write notes on
i) saturated solution
ii) unsaturated solution

22. a) What happens when MgSO4.7H2O is heated? Write the appropriate equation
b) Define solubility

23. In what way hygroscopic substances differ from deliquescent substances.

24. What are called thermolysis reactions?

25. How does pH play an important role in everyday life?

26. What is a chemical equilibrium? What are its characteristics?

27. What is called homologous series? Give any three of its characteristics?

28. Give the balanced chemical equation of the following reactions:
(i) Neutralization of NaOH with ethanoic acid.
(ii) Evolution of carbon dioxide by the action of ethanoic acid with NaHCO3.
(iii) Oxidation of ethanol by acidified potassium dichromate.
(iv) Combustion of ethanol.

29. Explain the mechanism of cleansing action of soap.

30. Name the three basic tissues system in flowering plants.

31. What is photosynthesis and where in a cell does it occur?

32. Write the reaction for photosynthesis?

33. Why are the rings of cartilages found in trachea of rabbit?

34. Leeches do not have secretion of digestive juices and enzymes -Why?

35. How is the digestive system of rabbit suited for herbivorous mode of feeding?

36. What is cohesion?

37. What would happen to the leaves of a plant that transpires more water than its absorption in the roots?

38. Differentiate between systemic circulation and pulmonary circulation.

39. Differentiate between Voluntary and involuntary actions.

40. Medullated and non-medullated nerve fibre.

41. What is bolting? How can it be induced artificially?

42. What will you do to prevent leaf fall and fruit drop in plants? Support your answer with reason.

43. Why are thyroid hormones refered as personality hormone?

44. How can menstrual hygiene be maintained during menstrual days?

45. Identify the parts A, B, C and D

46. Write the events involved in the sexual reproduction of a flowering plant.
a. Discuss the first event and write the types.

47. Why did Mendel select pea plant for his experiments?

48. What are allosomes?

49. A pure tall plant (TT) is crossed with pure dwarf plant (tt), What would be the F1 and F2 generations? Explain.

50. Why is Archaeopteryx considered to be a connecting link?

51. Define Ethnobotany and write its importance.

52. How can you determine the age of the fossils?

53. Discuss the method of breeding for disease resistance.

54. Name two maize hybrids rich in amino acid lysine.

55. How are stem cells useful in regenerative process?

56. What are the various routes by which transmission of human immuno deficiency virus takes place?

57. How is a cancer cell different from a normal cell?

58. Name any three foods that are to be avoided and included in the diet of a diabetic patient. Why should it be followed?

59. What is the importance of rainwater harvesting?

60. What are the consequences of deforestation?

61. How would you dispose the following wastes?
a. Domestic wastes like vegetable peels
b. Industrial wastes like metallic cans Can the disposal protect the environment? How?

62. Program for print the word “Hello” with sound