# A food scientist is checking the purity of a sample of vanilla flavouring before it is used in a product. She carries out paper chromatography using two solvents. In solvent A, the sample produces a single spot. In solvent B, the sample produces three spots. Explain what these results tell the scientist about the vanilla flavouring sample.

> WJEC GCSE Chemistry (Wales) — 1.1 The nature of substances and chemical reactions · Explain · 4 marks

## Mark scheme (4 marks)

1. A pure compound produces a single spot in all solvents
2. The result in solvent B shows the sample is a mixture / is not a pure substance
3. The sample contains at least three different compounds / substances
4. The compounds separate because they have different solubilities in the mobile phase / travel different distances because they distribute differently between the mobile and stationary phases

## Key terms

- [paper chromatography](https://www.gradenine.co.uk/glossary/paper-chromatography)

## Related

- [Revision notes for WJEC GCSE Chemistry (Wales)](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/a-food-scientist-is-checking-the-01163e29) · Published by Druglandscape Ltd.