Q1 Describe briefly how rocks are weathered?

1. Q1 Describe briefly how rocks are weathered? Ans: By physical weathering and Chemical weathering

2. Q2 Which of the following substance can sublimes to form vapour on heating? a) Stone b) Ice c) Iodine solid d) Glass Ans: c

3. Q3 Describe the steps of fractional distillation.

4. Answer: in textbook page 57. • The components of air can be separated to their differences in boiling points. • The air is first liquefied by repeated cooling and compression. The liquid air is warmed up slowly. Different gases in air boil at diff. Temp. and we can collect them one by one.

5. Q4 Xenon is in Group VIII. Is Xenon(Xe)stable? Why?

6. Ans: Yes. Because Xenon has an octet of • electrons./ • 8 electrons in the outermost • shell.

7. Q5 Give two differences between the properties of Group I elements and Group VII elements?

8. Ans: • Reactivity of Group I elements increases down the group but Group VII elements decreases down the group, and • Group I elements are reactive metals while Group VII elements are poisonous non-metals.

9. Q6 Give 2 uses of noble gases.

10. Ans. ( Textbk. P. 63 ) - Helium is used to fill airships. - Neon is used in advertising signs. - Argon is used to fill light bulbs.

11. Q7 An element X occurs naturally as a mixture of two isotopes. The relative isotopic masses of the two isotopes are 63.0 and 65.0. The relative atomic mass of X is 63.6. What is the percentage abundance of the two isotopes?

12. Let the relative abundance of 63X and 65X be y% and (100-y)% respectively. Relative atomic mass of X =Weighted average mass of the isotopes 63.6 = 63 xy + 65 x (100 - y) 100 6360 = 63y + 6500 – 65yy = 70 Therefore the relative abundance of 63X is 70% while that 65X is 30%

13. Q8 A chemist had a red powder. When the red powder was heated strongly, a silvery liquid and a colourless gas formed. Is the red powder an element or a compound? Explain your answer.

14. ANS: • It is a compound. It can be broken down into two simpler substances, the silvery liquid and the colourless gas.

15. Q9 Give three uses of limestone

16. ANS: • Constructing buildings • Building roads • Making glass, steel, concrete, cement, paper and mortar. • Neutralize the soil

17. Q10 Give two uses of aluminium.

18. ANS: • aircraft body,overhead power cables.

19. Q11 Hydrogen is the lightest gas, but why don’t we use it in filling airships?

20. Ans: Because it is explosive and can cause explosion.

21. Q12 In which group and period does Bromine belong to ? (Br atom has 7 e- in the outermost e- shell and has 4 e- shells)

22. Ans: Period: 4 Group: VII (Halogens)

23. Q13 Is Bromine(Gp VII) stable or not? Why?

24. Ans: Bromine is not stable as it has only 7 e- in the outermost e- shell and does not have an octet structure.

25. Q14 Is it easier for the metal atom to gain or to lose electrons ? Why?

26. Ans: It is easier for the metal atoms to lose e- than to gain e- to form ions (cat- or an-). Why? It requires less energy.

27. Q15 What is the meaning of isotopes?

28. Ans: Isotopes are atoms of the same element having same no. of p+ and e- but different no. of neutrons.

29. Q16 In an atom, which sub- atomic particle is positive and which one is negative?

30. Ans: Protons - positive Electrons - negative

31. Q17 State two physical weathering?

32. Ans: 1. Weathering by temperature changes: when rocks get hot in daytime but cool down quickly at night. 2. Weathering by frost action :when water freezes and expands to form ice, the rocks break apart.

33. Q18 How to obtain pure metal from ore?

34. Ans: First , mining of the ore , then concentrating the ore , and extraction of metal from concentrated ore , last purification of the impure metal.

35. Q19 How can we test for carbonate ions and what is the expected observation?

36. Ans: Add the sample into a test tube of hydrochloric acid and use the limewater to test for the gas. If the limewater turns milky, that means carbon dioxide is present. Then the sample must contain carbonate ion.

37. Q20 How can we determine whether a solid is a metal or non-metal? Please draw the experimental set-up.

38. Q21 Which metal is used to make supersonic aircraft ? Give 2 reasons to support your answer.

39. Ans: Titanium. It is because titanium is light, corrosion resistant, strong and malleable.

40. Q22 What are the special names of GROUP 1 GROUP 2, GROUP 7 & GROUP 0 ?

41. Ans: • GROUP 1: Alkali metals • CROUP 2: Alkaline earth metals • GROUP 7: Halogens • GROUP 0: Noble gases

42. Q23 What is the difference between Weathering & Erosion?

43. Ans: Weathering of rocks is the slow process in which exposed rocks are broken down into smaller pieces, but erosion of rocks is slow process in which weathered rock pieces are transported away by gravity, wind and water.

44. Q24 The element bromine has two isotopes and relative atomic mass of 79.9. What is the difference in structure between the isotopes of bromine ?

45. Q25 For each of the common changes listed below, determine whether it is a physical change or chemical change. Give you reason(s) for each case. • a) Making alcohol form grapes. • b) Making ice from water. • c) Electrolysis of water.

46. Ans: a. Chemical change. A new substance (alcohol) is formed from grape. b. Physical change. No new substances is formed; water is only changed from liquid to solid state. c. Chemical change. New substance are formed. They are hydrogen and oxygen.

47. Q26 Give 2 advantages of using aluminium to make overhead power cable.

48. Ans: • Low density • Ductile • Very good conductor of electricity • Cheaper than copper

49. Q27 Why the accurate relative atomic masses of elements are very seldom whole numbers?

50. Ans: The elements might contain several isotopes in different proportions.