Using the Earth's resources and sustainable development: Finite resources from the Earth, oceans and atmosphere are processed to provide energy and materials.

The idea

Earth supplies a fixed stock of raw materials. Finite means the total amount cannot be replaced once used, so extraction rates matter. The crust yields metal ores such as haematite, as well as other resources like limestone and crude oil; the oceans supply water, sodium chloride and dissolved minerals; the atmosphere supplies nitrogen and oxygen. These natural resources are not useful directly in most cases, so they undergo processing. Crude oil is separated by fractional distillation and cracked to give fuels and feedstock for polymers. Iron ore is reduced in a blast furnace to make iron and then steel. Seawater is desalinated or electrolysed to give chlorine and sodium hydroxide. Each process needs energy, often from burning finite fossil fuels, and produces waste, so chemists must balance product yield against environmental cost.

What earns the marks

• State that finite resources cannot be replaced once they are used up, so their supply is limited.
• Identify examples from each sphere: metal ores and crude oil from the Earth, water and sodium chloride from the oceans, nitrogen and oxygen from the atmosphere.
• Explain that raw materials are processed, for example fractional distillation of crude oil or reduction of iron ore, before they provide useful energy or materials.
• Recognise that processing requires energy and can produce waste or emissions, so it has environmental and economic costs.
• Link the idea of finite supply to the need to conserve resources, recycle metals and develop renewable alternatives.

Common mistakes and how to put them right

• Saying finite means 'will run out soon' rather than that the total quantity is limited and cannot be replenished.

  Put it right by defining finite as a fixed stock that is used up permanently.

• Treating air or seawater as infinite because they are abundant.

  Put it right by noting that useful components such as helium or fresh water can still be limited or costly to obtain.

• Assuming all resources are used directly.

  Put it right by giving a processing step, such as cracking crude oil fractions to make alkenes for polymers.

Exam tips

• Name the sphere for each resource you quote, for example 'haematite from the Earth's crust', to show precise knowledge.
• When asked why a resource is finite, refer to the rate of formation being far slower than the rate of use.
• Use a named process and its product to show how a raw material becomes a useful energy source or material.