# Crude oil is a mixture of alkanes. Describe how fractional distillation separates crude oil into fractions, and state one use of the fraction obtained at the lowest temperature.

> Cambridge International IGCSE Chemistry (0620) — 11.4 Alkanes · Describe · 4 marks

> Crude oil is a finite resource formed over millions of years from the remains of ancient organisms. It is an important source of fuels and chemical feedstocks.

## Mark scheme (4 marks)

1. Crude oil is heated / vaporised and the vapours enter a fractionating column
2. The column has a temperature gradient — hotter at the bottom, cooler at the top
3. Fractions condense and are collected at different levels because they have different boiling points
4. The fraction collected at the lowest temperature (refinery gas / LPG) is used as a fuel / bottled gas / 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 Cambridge International IGCSE Chemistry (0620)](https://www.gradenine.co.uk/learn)
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Source: [GradeNine](https://www.gradenine.co.uk/q/crude-oil-is-a-mixture-of-59ef038e) · Published by Druglandscape Ltd.