# Describe how fractional distillation is used to separate crude oil into fractions, and explain why fractions collected near the top of the fractionating column are more useful as fuels than those collected near the bottom.

> AQA GCSE Chemistry (8462) — 4.7.1 Carbon compounds as fuels and feedstock · Describe and Explain · 4 marks

## Mark scheme (4 marks)

1. Crude oil is heated and the hydrocarbons evaporate / vaporise
2. Hydrocarbons condense / are collected at different levels because they have different boiling points
3. Fractions collected near the top have shorter/smaller molecules (lower boiling points)
4. Shorter-chain / smaller molecules are more flammable, making them better fuels

## Key terms

- [fractional distillation](https://www.gradenine.co.uk/glossary/fractional-distillation)
- [fractions](https://www.gradenine.co.uk/glossary/fractions)

## Related

- [Revision notes for AQA GCSE Chemistry (8462)](https://www.gradenine.co.uk/learn)
- [How to answer "Describe and Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/describe-how-fractional-distillation-is-used-85c6b32b) · Published by Druglandscape Ltd.