# A student is given two white powders. One powder is pure aspirin and the other is a mixture of aspirin and starch. Explain how the student could use melting point data to determine which powder is the pure substance, and what results would be expected for each powder.

> Eduqas A-Level Chemistry — 1.5 Energetics · Explain · 5 marks

> Aspirin is a pharmaceutical compound with a melting point of 135 °C.

## Mark scheme (5 marks)

1. Heat both powders and record the temperature(s) at which they melt
2. A pure substance has a sharp (single) melting point
3. The pure aspirin would melt sharply at 135 °C
4. A mixture melts over a range of temperatures
5. The aspirin and starch mixture would melt over a range of temperatures (below 135 °C)

## Key terms

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

## Related

- [Revision notes for Eduqas A-Level 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-is-given-two-white-da2a61da) · Published by Druglandscape Ltd.