GCSE Chemistry · AQA 8462 · Topic 4.10.1
Using the Earth's resources and obtaining potable water
Key points
- Finite resources (e.g. crude oil, metal ores) will run out; renewable resources (e.g. timber, crops) can be replaced. Chemistry helps make processes more sustainable.
- Potable water is water that is safe to drink; it is not pure in the chemical sense as it has dissolved substances. It needs low levels of salts and microbes.
- In the UK, fresh water from rain collects in lakes, rivers and ground water. It is filtered (wire mesh, then sand and gravel beds) and sterilised using chlorine, ozone or ultraviolet light.
- Where fresh water is scarce, desalination of sea water uses distillation or reverse osmosis; both need large amounts of energy.
- Waste water from homes, farms and industry is treated by screening and grit removal, sedimentation to give sewage sludge and effluent, anaerobic digestion of sludge and aerobic treatment of effluent.
- (Higher) Phytomining uses plants to absorb metal compounds; the plants are burned and the ash is processed. Bioleaching uses bacteria to make leachate solutions containing metal compounds. Copper is then obtained by displacement with scrap iron or by electrolysis.
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Humans use the Earth's natural resources for warmth, shelter, food and transport. This sub-topic covers sustainability, how we make water safe to drink, how waste water is treated and (Higher tier) newer ways to extract copper.
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