Using Earth’s resources · Grade 7
We use the Earth's resources for warmth, shelter, food, transport and materials. Some, such as crude oil and metal ores, are finite and will run out; others, such as wood and cotton, are renewable. Chemistry helps us use resources sustainably: making water safe to drink, comparing products with life cycle assessments, and reducing, reusing and recycling.
Key facts
- Finite resources (crude oil, natural gas, coal, metal ores) cannot be replaced as fast as they are used. Renewable resources (wood, cotton, wool, food crops) can be grown again.
- Sustainable development meets the needs of people today without harming the ability of future generations to meet theirs.
- Potable water is safe to drink. It is not pure: it contains small amounts of dissolved substances.
- Fresh water is made safe by passing it through wire meshes, filtering it through sand and gravel beds, then sterilising it with chlorine, ozone or ultraviolet light.
- Sea water can be made drinkable by distillation or reverse osmosis (desalination), but this needs a lot of energy.
- A life cycle assessment (LCA) looks at a product's effect on the environment at each stage: raw materials, manufacture, use and disposal.
- Reducing, reusing and recycling saves finite resources and energy and cuts waste. Metals and glass are recycled by melting them and making new products.