S2 Science: The Water Cycle And Sewage Treatment (Paper 1 (basics))

S2 Science: The Water Cycle and Sewage Treatment (Paper 1 (basics))

2026-11-14

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Tutor Prep Guide · The processes of the water cycle, the ratio of fresh to salt water, the order of water and sewage treatment, and BOD with water saving figures

S2 Science: The Water Cycle and Sewage Treatment (Paper 1 (basics))

This paper covers the basic processes of the water cycle, the ratio of fresh to salt water and the difference between distillation and filtration.

Direct answers　Evaporation goes liquid to gas and condensation the other way, and dissolved salt passes a filter so distillation is needed.

01　Paper details (check answers afterwards)

Item	Detail
Questions	10
Suggested time	20
Difficulty mix	Foundation 3 · Intermediate 3 · Challenge 3 · Error redo 1
Chapter	Chapter: S2 Science: The Water Cycle and Sewage Treatment
Level	S2

02　Questions (10 items)

FoundationWhat is the main energy source of the water cycle?
FoundationWhat is the change from liquid water to water vapour called?
FoundationWhat is the process in which water vapour cools into tiny droplets aloft called?
IntermediateAbout how much of the water on Earth is salt water?
IntermediateSea water is about 3.5 per cent salt. How many grams of salt are in 1 kg of it?
IntermediateWhich kind of method removes salt that is dissolved in water?
ChallengeCan fresh water be obtained by filtering sea water through filter paper?
ChallengeAbout how many kilograms of fresh water come from distilling 100 kg of sea water containing 3.5 per cent salt?
ChallengeOne person uses 150 L of water a day. How many cubic metres is that in 30 days?
Error redoA student says distilled water must contain impurities and so cannot be drunk. What is wrong?

03　Answers and one-line notes

#	Answer	One-line note
1	Heat energy from the Sun	The Sun drives evaporation while gravity only moves precipitation and run-off.
2	Evaporation	Evaporation happens over the sea, lakes and soil at once and needs no boiling.
3	Condensation	Condensation builds the droplets that form clouds, and a raindrop must grow heavy enough to fall.
4	About 97 per cent, and fresh water is only about 3 per cent	97 plus 3 makes 100, and most of that fresh water is frozen in glaciers and ice caps.
5	35 g	3.5 per cent of 1 kg is 35 g, and the remaining 965 g is water.
6	Distillation or reverse osmosis	Dissolved salt particles are too small for a filter, so the water must be turned into vapour and condensed.
7	No, dissolved salt passes through the paper with the water	A filter only traps insoluble solids, which is the commonest confusion in water treatment.
8	About 96.5 kg	The 3.5 kg of salt stays behind in the vessel, so the distillate is 96.5 kg of water.
9	4.5 m³	150 times 30 is 4500 L, and 1 m³ equals 1000 L.
10	Distilled water is almost free of impurities; the real issue is that it lacks minerals	Distillation removes salt and most pollutants, and lacking minerals is not the same as containing impurities.

04　What to do after marking

After marking, redo only the wrong items and write down which step went wrong (formula, unit, or misread number).
Repeat the same item two days later; move to the next paper only when both attempts are correct.
Parents only need the answer and note columns; there is no need to explain every item.

For water cycle questions ask three things: which way the water changes state, whether the question asks about a quantity or a concentration, and whether the treatment is physical, biological or chemical.Tutor Registration →

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