# A student carries out paper chromatography on a sample of black ink and finds that three separate spots appear on the paper. Explain what this result tells the student about the ink, and describe the role of the mobile phase in separating the substances.

> WJEC GCSE Chemistry (Wales) — 1.5 Rate of chemical change · Explain · 4 marks

> Paper chromatography is used to separate and identify substances in a mixture. The technique relies on a stationary phase and a mobile phase.

## Mark scheme (4 marks)

1. The black ink is a mixture (not a pure substance)
2. A pure compound would produce only a single spot
3. The mobile phase (solvent) carries the substances through / up the paper
4. Substances separate because they have different solubilities in the mobile phase / travel different distances depending on how soluble they are

## Key terms

- [mobile phase](https://www.gradenine.co.uk/glossary/mobile-phase)
- [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-student-carries-out-paper-chromatography-ecba7790) · Published by Druglandscape Ltd.