Changes Around Us Important Questions

8th Standard EM

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Science

Time : 01:00:00 Hrs
Total Marks : 50
    6 x 1 = 6
  1. Burning of paper is a______ change.

    (a)

    Physical

    (b)

    chemical

    (c)

    physical & chemical

    (d)

    neutral

  2. The burning of matchstick is an example for chemical reaction based on______

    (a)

    Contact

    (b)

    electricity

    (c)

    light

    (d)

    catalyst

  3. Brine is a concentrated solution of ______.

    (a)

    Sodium sulphate

    (b)

    sodium chloride

    (c)

    calcium chloride

    (d)

    sodium bromide

  4. In Haber’s process of producing ammonia ______ is used as a catalyst.

    (a)

    Nitrogen

    (b)

    hydrogen

    (c)

    iron

    (d)

    nickel

  5. ______ is responsible for Global warming.

    (a)

    Carbon di oxide

    (b)

    methane

    (c)

    chlorofluoro carbons

    (d)

    all the above

  6. Rusting of iron is a _________ change.

    (a)

    physical

    (b)

    chemical

    (c)

    physical and chemical

    (d)

    neutral

  7. 5 x 1 = 5
  8. Reactants → ______.

    ()

    Products

  9. Iron objects undergo rusting when exposed to ______ and ______.

    ()

    Water, Oxygen

  10. Electrolysis of Brine solution gives ______ gases.

    ()

    Chlorine and hydrogen

  11. ______ is the enzyme responsible for browning of vegetables, fruits.

    ()

    Polyphenol oxidase or tyrosinase.

  12. The sides of the matchbox contains _________

    ()

    Red phosphorous

  13. 5 x 1 = 5
  14. Rusting

  15. (1)

    Decomposition of limestone

  16. Thermolysis

  17. (2)

    oxygen

  18. Catalysis

  19. (3)

    Iron

  20. Tarnishing

  21. (4)

    Decomposition

  22. Calcium Oxide

  23. (5)

    Haber's process

    2 x 2 = 4
  24. Fertilizers: Land pollution :: Oil spillage: _________

  25. Iron in water and air: Brown colour :: Iron in copper sulphate solution:_________

  26. 3 x 2 = 6
  27. Brine solution undergoes photolysis to give hydrogen and chlorine gas along with sodium hydroxide.

  28. In vanaspathi ghee (dalda) preparation finely divided platinum is used as a catalyst.

  29. Silver articles become black on exposure to atmospheric air

  30. 4 x 2 = 8
  31. Define a chemical reaction.

  32. What is pollution?

  33. Why photosynthesis is a chemical reaction?

  34. What is rusting?

  35. 2 x 3 = 6
  36. Explain the role of yeast in making cakes?

  37. Do all the fruits and vegetables undergo browning? Explain.

  38. 2 x 5 = 10
  39. Explain the three types of pollution.

  40. Explain any three conditions that is required for a chemical reaction to take place by citing one example each.

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