# A student is testing three food samples for the presence of lipids using the emulsion test. Describe how the student should carry out the emulsion test and state what a positive result looks like.

> AQA A-Level Biology (7402) — 3.1.3 Lipids · Describe · 5 marks

## Mark scheme (5 marks)

1. Add ethanol to the food sample (and shake / mix)
2. Pour / add the ethanol solution into water
3. A cloudy white emulsion forms as a positive result
4. A negative result remains clear / colourless
5. The cloudiness is caused by lipid droplets being suspended / dispersed in the water

## Key terms

- [emulsion test](https://www.gradenine.co.uk/glossary/emulsion-test)
- [lipid](https://www.gradenine.co.uk/glossary/lipid)
- [emulsion](https://www.gradenine.co.uk/glossary/emulsion)

## Related

- [Revision notes for AQA A-Level Biology (7402)](https://www.gradenine.co.uk/learn)
- [How to answer "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-student-is-testing-three-food-ed4bcdff) · Published by Druglandscape Ltd.