Edexcel GCSE Combined Science CC8 Fuels and Earth science: a complete overview of crude oil, combustion, the atmosphere and climate change

What CC8 actually demands

Fuels and Earth science, on Chemistry Paper 2, covers where our fuels come from, what burning them produces, and how the atmosphere formed and is changing. The examiners reward the fractional-distillation explanation, the products of complete and incomplete combustion, and a clear account of the greenhouse effect and climate change.

This guide walks through the topic and ties together the matching dot-point pages, each with its own practice questions.

Crude oil, fractions and combustion

Crude oil is a mixture of hydrocarbons (hydrogen and carbon only), separated by fractional distillation using their different boiling points. As molecules get larger, the boiling point rises, the liquid is more viscous, and it is less flammable and volatile.

Complete combustion (plenty of oxygen) gives carbon dioxide and water; incomplete combustion (limited oxygen) also gives carbon monoxide and soot. Pollutants include carbon dioxide (greenhouse gas), carbon monoxide (toxic), and sulfur dioxide and nitrogen oxides (acid rain).

The atmosphere and climate change

The early atmosphere (from volcanoes) was rich in carbon dioxide with little oxygen. Carbon dioxide fell (dissolving in oceans, photosynthesis, locked in rocks) and oxygen rose (photosynthesis). Today: about 78% nitrogen, 21% oxygen, 1% other.

Greenhouse gases (carbon dioxide, methane) trap heat. Human activity is increasing them, causing climate change with consequences such as melting ice and rising sea levels.

How CC8 is examined

• Fractional distillation. Explaining how the column separates the fractions.
• Combustion. Writing the products of complete and incomplete combustion and the dangers.
• The atmosphere. Describing how carbon dioxide fell and oxygen rose.
• Climate change. Explaining the greenhouse effect and naming consequences.

Check your knowledge

A mix of recall and explanation questions covering CC8. Attempt them under timed conditions, then check against the solutions.

1. Define a hydrocarbon. (1 mark)
2. What property is used to separate crude oil by fractional distillation? (1 mark)
3. State the products of complete combustion of a hydrocarbon. (2 marks)
4. Name the toxic gas from incomplete combustion. (1 mark)
5. Name two pollutants that cause acid rain. (2 marks)
6. State the approximate percentage of oxygen in the atmosphere today. (1 mark)
7. Explain why oxygen increased in the early atmosphere. (1 mark)
8. Name two greenhouse gases. (1 mark)