# A student has two white powders, substance A and substance B. She wants to find out which one is a pure substance and which one is a mixture. She heats samples of each powder and records the temperature at which each one melts. Substance A melts completely at exactly 58 °C. Substance B begins to soften at 49 °C and is fully melted by 61 °C. Explain what the melting point data tells the student about the purity of each substance.

> Eduqas GCSE Chemistry — 1.5 Rate of chemical change · Explain · 4 marks

## Mark scheme (4 marks)

1. Substance A is a pure substance
2. Because substance A has a sharp (single/specific) melting point
3. Substance B is a mixture
4. Because substance B melts over a range of temperatures

## 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 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-has-two-white-powders-7595112b) · Published by Druglandscape Ltd.