# A food scientist wants to separate a mixture of two liquids — ethanol (boiling point 78 °C) and water (boiling point 100 °C) — to obtain pure samples of each liquid. Explain why simple distillation would not be suitable for this separation and describe how fractional distillation could be used instead.

> Edexcel GCSE Chemistry (1CH0) — 2.2 Methods of separating and purifying substances · Explain and Describe · 4 marks

## Mark scheme (4 marks)

1. Simple distillation is not suitable because both liquids have different but relatively close boiling points / simple distillation cannot separate two liquids from each other (it can only separate a liquid from a solution/dissolved solid).
2. Fractional distillation works because the two liquids have different boiling points.
3. The mixture is heated in a flask and passes through a fractionating column; the liquid with the lowest boiling point (ethanol, 78 °C) evaporates/rises first.
4. The vapour is then condensed (cooled) and collected as a pure liquid, leaving the other liquid (water) behind / the fractions are collected separately.

## Key terms

- [simple distillation](https://www.gradenine.co.uk/glossary/simple-distillation)
- [fractional distillation](https://www.gradenine.co.uk/glossary/fractional-distillation)
- [boiling point](https://www.gradenine.co.uk/glossary/boiling-point)
- [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 and Describe" 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/a-food-scientist-wants-to-separate-b30937d4) · Published by Druglandscape Ltd.