# Crude oil is separated into fractions by fractional distillation. Explain why the different fractions are collected at different heights in the fractionating column, and state one use of the fraction collected near the top of the column.

> Edexcel GCSE Chemistry (1CH0) — 10.1 Crude oil, hydrocarbons and alkanes (Chem only) · Explain · 4 marks

> Crude oil is a mixture of hydrocarbons. It is separated into useful fractions by fractional distillation in an oil refinery.

## Mark scheme (4 marks)

1. The fractions have different boiling points (due to different chain lengths / molecular sizes)
2. The column has a temperature gradient — hotter at the bottom and cooler at the top
3. Hydrocarbons with lower boiling points rise higher before condensing / shorter chain hydrocarbons condense higher up
4. Fractions collected near the top have short chains / low boiling points — named use e.g. petrol (fuel for cars), or used as fuel / as a feedstock for making chemicals / LPG for camping gas

## Key terms

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

## Related

- [Revision notes for Edexcel GCSE Chemistry (1CH0)](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-fractions-9c827fa1) · Published by Druglandscape Ltd.