Cleaning used water, a model watershed and thirst by the sea
Answers are for parents and teachers.
1
Draw a flow chart of the way used water travels from your sink to a treatment plant and then to a farm.
Boxes with arrows: sink → pipes → screens → tanks → tests → farm.
2
Explain, in two sentences, what “we all live downstream” means. Give one example from Egypt.
Water carries what is in it downhill, so pollution upstream reaches those below. Example: waste thrown into the Nile in one place can reach towns farther along the river.
3
A school treats 1000 L of used water. 700 L waters the garden and the rest flushes toilets. How many litres flush toilets?
1000 − 700 = 300 L.
4
Sea water has about 35 g of salt in each litre. How much salt is in 5 L?
5 × 35 = 175 g.
5
Write a claim, evidence and reasoning to answer: can we drink sea water if we leave it in the Sun?
Claim: no, the water that is left is still salty. Evidence: in the saucer test the salt stayed behind. Reasoning: only the water evaporates, so what remains is salt, and the vapour must be caught and cooled to get fresh water.