# Crude oil is a finite resource that is separated into useful fractions by fractional distillation. Describe how fractional distillation separates crude oil into fractions, and explain why different fractions are collected at different heights in the fractionating column.

> Pearson Edexcel International GCSE Chemistry (4CH1) — 4.2 Crude oil · Describe and Explain · 4 marks

> Crude oil is a mixture of hydrocarbons with different boiling points. It is processed at an oil refinery to produce fuels and other useful products.

## Mark scheme (4 marks)

1. Crude oil is heated / vaporised so the hydrocarbons turn into gas / vapour
2. The vapour rises up the fractionating column, where there is a temperature gradient — hotter at the bottom and cooler at the top
3. Hydrocarbons condense when the temperature in the column falls to / reaches their boiling point, and are collected as a liquid fraction
4. Fractions with higher boiling points (longer chain / larger molecules) condense lower down the column, whilst fractions with lower boiling points (shorter chain / smaller molecules) condense higher up / exit as gas at the top

## Key terms

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

## Related

- [Revision notes for Pearson Edexcel International GCSE Chemistry (4CH1)](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/crude-oil-is-a-finite-resource-3211821c) · Published by Druglandscape Ltd.