# A student carries out paper chromatography on a sample of black ink to find out whether it is a pure substance or a mixture. The solvent travels 8.0 cm up the paper. Three separate spots are produced, travelling distances of 2.0 cm, 4.8 cm and 7.2 cm from the baseline. Explain what the results of this experiment tell the student about the black ink, and describe how the mobile phase and stationary phase are involved in producing the separation.

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

## Mark scheme (4 marks)

1. Three spots show the black ink is a mixture (not a pure substance), because a pure substance produces only one spot
2. The solvent (mobile phase) carries the substances up the paper as it moves
3. The paper acts as the stationary phase and does not move
4. The substances separate because they have different solubilities in the mobile phase / they are attracted to the stationary phase to different extents, so they travel different distances

## Key terms

- [paper chromatography](https://www.gradenine.co.uk/glossary/paper-chromatography)
- [mobile phase](https://www.gradenine.co.uk/glossary/mobile-phase)
- [stationary phase](https://www.gradenine.co.uk/glossary/stationary-phase)
- [mixture](https://www.gradenine.co.uk/glossary/mixture)
- [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-student-carries-out-paper-chromatography-bee212df) · Published by Druglandscape Ltd.