# Crude oil is separated into useful products using fractional distillation. Explain how fractional distillation works to separate the different fractions in crude oil.

> WJEC A-Level Chemistry (Wales) — 1.8 Redox · Explain · 5 marks

> Crude oil is a mixture of many hydrocarbons. It is fed into a fractionating column where the different fractions are collected at different levels.

## Mark scheme (5 marks)

1. Crude oil is heated so that it evaporates / vaporises
2. The different hydrocarbons / fractions have different boiling points
3. The vapour rises up the fractionating column and cools
4. Each fraction condenses / turns back to liquid at the level where the temperature matches its boiling point
5. The fractions are tapped off / collected at different levels of the column

## Key terms

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

## Related

- [Revision notes for WJEC A-Level Chemistry (Wales)](https://www.gradenine.co.uk/learn)
- [How to answer "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/crude-oil-is-separated-into-useful-255d0071) · Published by Druglandscape Ltd.