AQA · GCSE · Chemistry
Course version: 8462 · Version from Sept 2018
The methods used to produce potable water depend on available supplies of…
Full specification wording
Potable water: The methods used to produce potable water depend on available supplies of water and local conditions.
The treatment used to make water potable is not the same everywhere.
Checked against the AQA 8462 specification (opens in a new tab) on .
- Point 5 of 12
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
The treatment used to make water potable is not the same everywhere. It depends on what water is available and local conditions. For example, in the UK, rain collected in reservoirs or aquifers is usually treated by filtration to remove solids and chlorination to kill microbes. In dry coastal areas, sea water may be desalinated by distillation or reverse osmosis, which is expensive and energy-intensive. If water contains high levels of dissolved salts, desalination is needed; if it mainly contains microbes, chlorination may be sufficient.
What earns the marks
- States that the choice of treatment depends on the water source and local conditions.
- Describes typical treatments for fresh water, such as filtration and chlorination.
- Describes desalination for sea water or water with high salt levels.
- Explains why desalination is used in some locations but not others, linking to energy cost or availability.
- Selects an appropriate method for a given water source and justifies the choice.
Common mistakes and how to put them right
Assuming all water is treated in the same way.
Put it right: Treatment depends on the impurities present and local factors.
Thinking desalination is always used.
Put it right: It is used where fresh water is scarce or salt levels are high.
Confusing filtration with chlorination.
Put it right: Filtration removes insoluble solids, chlorination kills microbes.
Exam tips
- When given a water source, identify the main impurity before choosing a treatment.
- Use local context, such as coastal or arid regions, to justify desalination.
- Compare methods by cost and energy use where the question asks for evaluation.
- Remember that potable water production must be safe, so multiple steps may be needed.
Try the lesson
The start of the Potable water: The methods used to produce potable water depend on available supplies of water and local conditions. lesson, made from checked teaching notes for this specification point.
Have a go first
Which factor determines the method a region uses to produce potable water?
Listen
The treatment used to make water potable is not the same everywhere. It depends on what water is available and local conditions. For example, in the UK, rain collected in reservoirs or aquifers is usually treated by filtration to remove solids and chlorination to kill microbes. In dry coastal areas, sea water may be desalinated by distillation or reverse osmosis, which is expensive and energy-intensive. If water contains high levels of dissolved salts, desalination is needed; if it mainly contains microbes, chlorination may be sufficient. A strong answer earns marks for these points. States that the choice of treatment depends on the water source and local conditions. Describes typical treatments for fresh water, such as filtration and chlorination. Describes desalination for sea water or water with high salt levels. Explains why desalination is used in some locations but not others, linking to energy cost or availability. A common slip: Assuming all water is treated in the same way. Instead, treatment depends on the impurities present and local factors. Exam tip: When given a water source, identify the main impurity before choosing a treatment.
See it
Key words
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Water treatment methods
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Local and global water availability
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Cost and energy in water production
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Appropriate technology and sustainability
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See every definition
- Water treatment methods
- The methods used to produce potable water depend on available supplies of water and local conditions.
- Local and global water availability
- The choice of treatment depends on the water source and local conditions, so treatment is not the same everywhere.
- Cost and energy in water production
- Desalination by distillation or reverse osmosis is expensive and energy-intensive, which explains why it is used in some locations but not others.
- Appropriate technology and sustainability
- A suitable treatment is chosen based on the source, such as filtration and chlorination for fresh water or desalination for sea water or water with high salt levels.
Label the diagram
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