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GCSE Chemistry · key term
The removal of dissolved salts from salty water.
Used by AQA and OCR
Specification 4.10.1.2, 4.10.1.3 · Paper 2
The removal of dissolved salts from salty water or seawater.
Revise: Water Treatment and PotabilityDesalination by distillation or a membrane process such as reverse osmosis is required, followed by any further treatment needed to make the supply safe.
The removal of dissolved salts from salty or sea water.
Link each treatment step to its purpose: filter beds remove insoluble material; sterilisation kills microbes; desalination removes dissolved salts.
When comparing sources, explain that fresh water generally needs filtration and sterilisation, whereas salty water also needs an energy-intensive desalination stage.
When comparing water sources, link ease of treatment to what must be removed and, for salt water, the high energy demand of desalination.
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Specification C6.3g · Paper 2 (Foundation), Paper 4 (Higher)
Revise: Water PotabilityGroundwater is often comparatively straightforward to make potable because it may contain fewer suspended particles than some surface water and does not usually need desalination. Its quality still varies: dissolved substances or contamination may call for extra treatment. Clear groundwater should never be assumed safe without testing and appropriate treatment.
Paper 1 (Foundation), Paper 2 (Foundation), Paper 3 (Higher), Paper 4 (Higher)
Removing dissolved salts from seawater or other salty water to obtain fresh water.
Revise: Potable water methodsPolluted groundwater may be difficult to treat, while the availability of cheap energy or suitable technology may make desalination more practical in a particular place. Choosing a water supply therefore involves balancing reliability, cost, energy use, waste disposal, health benefits and environmental effects.