Page 238 - ICSE Chemistry 8

15. Discuss the technique of gravita on.
16. Discuss the ancient view on atomic structure.
17. What is atomic number?
18. What are isotopes?
19. Why do atoms of elements combine or react?
20. What is variable valency?
21. Write the symbols of the following elements: carbon, bromine, nickel and potassium.
22. Write the valency of the following elements: lithium, magnesium, boron and silicon.
23. Name any four elements exhibi ng variable valency.
24. Write the formulae and valency of the following radicals: carbonate, nitrate, phosphate and acetate.
25. What is a chemical equa on?
26. What happens when an iron nail is dropped in blue-coloured copper sulphate solu on? Write the
chemical equa on to represent the reac on.
27. How is an exothermic reac on diff erent from an endothermic reac on?
28. What are electrochemical reac ons?
29. What is photodecomposi on?
30. What is precipita on reac on?
31. What is ac vity series of metals?
32. How is hydrogen prepared from cold water?
33. What is electrolysis?
34. What happens when hydrogen combines with nitrogen?
35. What are the tests for hydrogen?
36. Write any four uses of water.
37. Diff eren ate between surface water and groundwater.
38. What is sedimenta on?
39. What is Tyndall eff ect?
40. How is deliquescence diff erent from effl orescence?
41. Write about some useful carbon products.
42. Discuss the occurrence of diamond.
43. Discuss the structure of graphite
44. Write the uses of buckminsterfullerene.
45. How is wood charcoal diff erent from ac vated charcoal?

D. Answer in detail.
1. What are the postulates of the kine c molecular theory of ma er?
2. Explain the existence of states of ma er based on the kine c molecular theory of ma er.
3. Write the proper es of solids.
4. With the help of an ac vity, observe the changes that occur when the ice melts.
5. With the help of an example, explain the law of conserva on of mass.
6. Classify the changes taking place around us into diff erent categories.
7. What is a physical change? Write the characteris cs of a physical change.
8. With the help of an ac vity, show that mel ng of ice is a physical change.
9. What is evapora on? How is the rate of evapora on aff ected by various factors?
10. Write a note on changes involving energy changes.
11. Write the characteris cs of mixtures. Diff eren ate between homogeneous mixtures and
heterogeneous mixtures.

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