# A technician is testing two samples of aspirin — one freshly prepared in a laboratory and one that has been stored for several years. Explain how melting point data could be used to determine which sample is purer, and what the results would indicate about the stored sample.

> OCR GCSE Chemistry A: Gateway Science (J248) — C2.1 Purity and separating mixtures · Explain · 4 marks

> Aspirin is a white crystalline solid. A pure substance has a sharp, defined melting point. Impure substances melt over a range of temperatures lower than the expected value.

## Mark scheme (4 marks)

1. A pure substance has a sharp melting point (melts at one specific temperature)
2. An impure substance melts over a range of temperatures (rather than at a single point)
3. The stored aspirin sample would have a lower melting point than the pure/fresh sample
4. This indicates the stored sample contains impurities / is less pure than the fresh sample

## Key terms

- [melting point data](https://www.gradenine.co.uk/glossary/melting-point-data)

## Related

- [Revision notes for OCR GCSE Chemistry A: Gateway Science (J248)](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-technician-is-testing-two-samples-fe32cf06) · Published by Druglandscape Ltd.