A water company makes potable water from the water in a reservoir.
The water in the reservoir is fresh water from rain. It contains soil, small pieces of solid and microorganisms.
The water company uses three stages.
Stage 1: The water is left to stand in a large tank, so that large pieces of solid settle at the bottom.
Stage 2: The water is passed through beds of sand.
Stage 3: Chlorine is added to the water.
What is meant by potable water?
Name the separation process used in Stage 1.
Explain the purpose of Stage 2 and Stage 3.
A student says, "Potable water is pure water."
Explain why the student is not correct.
In some dry countries, potable water is made from seawater.
Name the process used to remove the salt from seawater.
Seawater can be distilled to make potable water.
Describe how distillation separates potable water from seawater.
Give one reason why making potable water by distilling seawater is expensive.
51 exam-style questions on OCR GCSE Chemistry 6.3 Interpreting and interacting with earth systems, covering 6.3.1 Formation and evolution of the atmosphere, 6.3.2 The greenhouse effect and climate change, 6.3.3 Sources and problems of atmospheric pollutants, and 6.3.4 Producing potable water. Each one has a worked solution and a mark scheme showing where the marks go.