# A food colouring manufacturer claims that one of its yellow dyes is a pure substance. A chemist carries out paper chromatography on the yellow dye using two different solvents. In solvent A, the yellow dye produces a single spot. In solvent B, the yellow dye produces three separate spots. Explain what the results from both solvents tell the chemist about the yellow dye.

> Eduqas GCSE Chemistry — 1.4 The ever-changing Earth · Explain · 4 marks

## Mark scheme (4 marks)

1. A single spot in one solvent does not confirm purity on its own
2. The three spots in solvent B show the dye is a mixture / not a pure substance
3. A pure compound produces a single spot in all solvents
4. Therefore the yellow dye is not a pure substance / the manufacturer's claim is incorrect

## Key terms

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

## Related

- [Revision notes for Eduqas GCSE Chemistry](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-colouring-manufacturer-claims-that-2e853e90) · Published by Druglandscape Ltd.