Earth's finite resources, sustainable development, water treatment, potable water.
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CognitoResources and sustainability
Key facts & methods
Finite resources
Many of Earth's resources are finite (limited and non-renewable): fossil fuels, metal ores, some minerals.
Sustainable development: meeting present needs without compromising future generations.
Resources must be used efficiently and recycled where possible.
Conflict between economic development (exploiting resources) and sustainability.
Life cycle assessment (LCA) evaluates environmental impact of a product from extraction to disposal.
Obtaining potable water
Potable water: water that is safe to drink (not pure — contains dissolved minerals, which give water its taste).
UK (fresh water source): filter (remove large particles) → sedimentation → filter through sand/gravel → chlorination (kill microbes).
Seawater/salt water: desalination required. Two methods:
(1) Distillation: heat seawater → evaporate → condense. High energy cost.
(2) Reverse osmosis: force water through semi-permeable membrane under high pressure. Removes salt ions.
Waste water treatment
Sewage treatment: screening (remove large solids) → sedimentation (solids settle) → biological treatment (bacteria break down organic matter) → treated water returned to rivers.
Industrial waste water: may need specialist treatment to remove toxic metals or chemicals before release.
The treated water must meet strict legal standards before release into environment.
Life cycle assessment (LCA)
LCA evaluates the environmental impact of a product through its entire life:
Extraction of raw materials → manufacturing → use → disposal/end of life.
Considers: energy use, water use, CO2 emissions, waste produced, land use.
Allows comparison of products (e.g. glass vs plastic bottle) on environmental grounds.
Limitation: some data is difficult to quantify precisely; different weightings give different conclusions.
⚡ Show all working — the AI marks against the AQA mark scheme. Method marks awarded for correct working even if the final answer is wrong.
1 markPotable water definitionAQA 8462 style
What is meant by "potable water"?
A Completely pure water containing only H2O molecules
B Water that is safe to drink, with sufficiently low levels of dissolved substances and microbes
C Water from a natural spring, unprocessed
D Water that has been distilled to remove all dissolved substances
3 marksWater treatment stepsAQA 8462 style
Describe the stages involved in treating fresh river water to make it potable in the UK. (3 marks)
Hint: At least three stages in order: sedimentation → filtration → chlorination. Explain what each stage removes or does.
+30 XP
1 markDesalination methodAQA 8462 style
Which method of desalination uses a semi-permeable membrane?
A Distillation
B Reverse osmosis
C Filtration
D Chlorination
4 marksLCA comparisonAQA 8462 style
A manufacturer is deciding whether to use glass or plastic bottles for a product. Explain how a life cycle assessment would help them make a decision. Include two factors an LCA would consider. (3 marks)
Hint: LCA covers: extraction → manufacture → use → disposal. Name two specific factors and compare how glass and plastic differ for each.