10.2 Potable water
5 exam questions worth 9 marks. Write your answer, open the mark scheme, then give yourself the marks you earned. Your answers are saved on this device.
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What is potable water?
Choose one answer.
Correct Not quite: the answer is Water that is safe to drink
Mark scheme
B
Model answer
B: potable water is safe to drink.
Describe the main steps used to make fresh water in the UK potable.
Mark scheme
- choose a source / sedimentation (1)
- filtration through sand / gravel beds (1)
- sterilising with chlorine / ozone / UV (1)
Model answer
The water is left for solids to settle, filtered through beds of sand and gravel, then sterilised with chlorine, ozone or UV light.
Explain why water is sterilised.
Mark scheme
- to kill microbes / bacteria (1)
Model answer
To kill harmful microbes.
Give one method of desalination and one reason why it is expensive.
Mark scheme
- distillation / reverse osmosis (1)
- requires large amounts of energy (1)
Model answer
Distillation; it needs a lot of energy to boil the sea water.
Explain why distilled water, rather than tap water, is used in chemical analysis.
Mark scheme
- tap water contains dissolved salts / ions (1)
- these could react / interfere with the test and give false results (1)
Model answer
Tap water contains dissolved salts, which could react in the tests and give false results.
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