CBSE Class 10 Science | Top 45 Most Important Questions | For Board Exam 2025

Preparing for the CBSE board exams can be overwhelming, but focusing on important questions can make studying more efficient. Here are 45 crucial questions with answers, divided into Chemistry, Biology, and Physics, to help you score well.

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Chemistry (20 Questions)

Chemical Reactions and Equations

1. What type of reaction is the breakdown of glucose in the presence of oxygen?
   Exothermic reaction (cellular respiration).

2. What is the chemical formula for glucose?
   C6H12O6

3. What are the products of glucose reacting with oxygen?
   Carbon dioxide and water.

4. What is the significance of ATP in cellular respiration?
   ATP stores and provides energy for cellular processes.

5. What is the color change observed when silver chloride is exposed to sunlight?
   White to gray.

6. What is the chemical equation for the decomposition of silver chloride?
   2AgCl → 2Ag + Cl2

7. What is a common application of silver halides?
   Black and white photography.

Acids, Bases, and Salts

8. What is the chemical name for quick lime?
   Calcium oxide (CaO).

9. What is the product formed when quick lime reacts with water?
   Calcium hydroxide (Ca(OH)2).

10. What type of reaction is the combination of quick lime and water?
    Combination (and exothermic) reaction.

Metals and Non-Metals

11. What gas is responsible for the tarnishing of silver articles?
    Hydrogen sulfide (H2S).

12. What is the black substance formed on tarnished silver?
    Silver sulfide (Ag2S).

13. What is the process called when copper powder is heated in air and turns black?
    Oxidation (or combustion).

14. What is the black substance formed on heating copper powder in air?
    Copper oxide (CuO).

15. What type of reaction is the heating of copper powder in air?
    Combination reaction.

Chemical Reactions

16. What happens when ferrous sulfate crystals are heated?
    They decompose, producing ferric oxide, sulfur dioxide, and sulfur trioxide.

17. What is the color of ferrous sulfate crystals?
    Green.

18. What is the color of ferric oxide?
    Reddish-brown.

19. What type of reaction is the heating of ferrous sulfate crystals?
    Thermal decomposition.

20. What is observed when iron nails are dipped in copper sulfate solution?
    The blue color fades, and a green color (ferrous sulfate) appears. Copper metal is deposited on the nails.

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Biology (15 Questions)

Human Physiology

21. What are the three locations mentioned in the human alimentary canal?
    Buccal cavity, stomach, and small intestine.

22. What enzyme is present in the buccal cavity?
    Amylase.

23. What enzyme is present in the stomach?
    Pepsin.

24. What enzyme is present in the small intestine (mentioned in the context of pancreatic juice)?
    Trypsin.

Reproduction in Plants

25. What is vegetative propagation?
    A method of growing new plants from vegetative parts like roots, stems, or leaves.

26. What are the advantages of vegetative propagation?
    Genetically identical offspring, faster growth.

27. Give examples of plants that can be propagated vegetatively.
    Rose, jasmine, banana, orange, grapes, sugarcane, bryophyllum.

28. What is the difference between unisexual and bisexual flowers?
    Unisexual flowers have either male or female reproductive organs, while bisexual flowers have both.

29. Give examples of unisexual flowers.
    Watermelon, papaya.

30. Give examples of bisexual flowers.
    Mustard, hibiscus.

Human Eye and Vision

31. What is hypermetropia (farsightedness)?
    A condition where a person cannot see nearby objects clearly.

32. Which lens is used to correct hypermetropia?
    Convex lens.

33. Where does the image form in hypermetropia?
    Behind the retina.

34. What is the function of the retina in the eye?
    To receive and process light signals, forming an image.

35. What is the process of respiration?
    The process by which organisms obtain energy from glucose.

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Physics (10 Questions)

Electricity

36. What does the formula R = ρL/A represent?
    The relationship between resistance (R), resistivity (ρ), length (L), and cross-sectional area (A) of a wire.

37. If you have four wires of the same material, which will have the least resistance?
    The wire with the shortest length and largest diameter.

38. How is the diameter of a wire related to its resistance?
    Resistance is inversely proportional to the square of the diameter.

39. What is Ohm's Law?
    V = IR (Voltage = Current × Resistance).

40. What is the unit of resistance?
    Ohm (Ω).

41. What is the unit of current?
    Ampere (A).

42. What is the unit of voltage?
    Volt (V).

Mathematical Formulas

43. What is the formula for the area of a circle?
    A = πr² (where r is the radius).

44. How is the radius of a circle related to its diameter?
    Radius is half the diameter (r = d/2).

45. What is the importance of understanding chemical reactions?
    They are fundamental to many processes in science and technology, helping us predict and control various reactions.

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These key questions and answers will help students prepare effectively for their CBSE board exams. Keep revising and practicing regularly for the best results!