The mass story, sea water and slippery sand
Answers are for parents and teachers.
1
A pot of water has a mass of 800 g. After a grown-up boils it for 5 minutes the mass is 760 g. How much mass was lost, and where did it go?
800 − 760 = 40 g. It went into the air as water vapour.
2
Draw and label a model still: a bowl, salt water, a cup, a cover and the Sun. Add arrows for evaporating and condensing.
The drawing shows salt water in a bowl, a cup in the middle, a cover above, and arrows: vapour rising (evaporating) and drops forming on the cover and falling into the cup (condensing).
3
List three jobs of people who work to bring fresh water to a town from the sea, and say what each one does.
Answers differ, for example: an engineer designs the plant; an operator runs the machines; a scientist tests the water.
4
Write a claim, evidence and reasoning: does water on sand make a block easier to pull?
Claim: damp sand makes a block easier to pull. Evidence: the block needed an average of 6 coins on damp sand and 14 on dry sand. Reasoning: damp sand does not pile up, so there is less friction.
5
Tarek says, “The painting proves how the pyramids were built.” Explain why he should be more careful.
The painting is a clue about moving a statue, and the water idea is a theory supported by tests. It does not prove how the pyramids were built.