End-of-chapter questions 1
The water cycle and the carbon cycle are both of vital importance to life. Explain how they both depend on energy from the Sun.
2
Water is present in the atmosphere, in the seas and in ice and snow. a Describe a chemical test for water. Give the test and the positive result. b State one use of water in industry. c Water is a good solvent. What do you understand by the term solvent? d Water vapour in the atmosphere reacts with sulfur dioxide, SO2, to produce acid rain. i State one source of sulfur dioxide. ii State two adverse effects of acid rain. iii Calculate the relative molecular mass of sulfur dioxide. e Water from lakes and rivers can be treated to make the water safer to drink. Describe two of the steps in water purification. For each of these steps, give an explanation of its purpose. f Water is formed when hydrogen burns in air. State the percentage of oxygen present in the air.
[2] [1] [1] [1] [2] [1]
[4] [1]
[Cambridge IGCSE® Chemistry 0620/21, Question 3(a–e & f(i)), June 2011] S
3
The diagram below shows part of the water cycle. cloud H2O(I)
H2O(g)
Sun
rain land H2O(I)
a i
sea
State the name of each of the following changes of state. H2O(l) → H2O(g) H2O(g) → H2O(l)
[2]
ii Which one of the above changes of state is exothermic? Explain your choice. b The rain drains into rivers and then into reservoirs. Describe how water is treated before it enters the water supply. c Explain how acid rain is formed.
[1] [2] [4]
[Cambridge IGCSE® Chemistry 0620/31, Question 1(a, b & c(i)), June 2012]
4
Two important greenhouse gases are methane and carbon dioxide. a Methane is 20 times more effective as a greenhouse gas than carbon dioxide. The methane in the atmosphere comes from both natural and industrial sources. i Describe two natural sources of methane. ii Although methane can persist in the atmosphere for up to 15 years, it is eventually removed by oxidation. What are the products of this oxidation? b How do the processes of respiration, combustion and photosynthesis determine the percentage of carbon dioxide in the atmosphere?
[2] [2] [4]
[Cambridge IGCSE® Chemistry 0620/31, Question 2, November 2011]
Original material © Cambridge University Press 2014
Chapter 1: Planet Earth
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