# A student has prepared a mixture containing iron filings and sulfur powder. The student then heats the mixture strongly until a reaction occurs, producing a grey solid. Explain why the method used to separate the original mixture of iron filings and sulfur powder could not be used to separate the grey solid back into iron and sulfur.

> Edexcel GCSE Chemistry (1CH0) — 1.2 Methods of separating and purifying substances · Explain · 4 marks

> Iron and sulfur can be mixed together or chemically combined to form a compound. The original mixture can be separated using a magnet. When iron and sulfur are heated together, a chemical reaction occurs and a grey solid is formed.

## Mark scheme (4 marks)

1. The original mixture could be separated because iron is magnetic (and is attracted to a magnet)
2. In the grey solid (iron sulfide), the iron and sulfur are chemically combined / have reacted together to form a compound
3. The iron in the compound is no longer magnetic / does not retain its magnetic properties
4. Physical separation methods (such as using a magnet) cannot separate a compound / you would need a chemical reaction to separate a compound

## Key terms

- [mixture](https://www.gradenine.co.uk/glossary/mixture)

## Related

- [Revision notes for Edexcel GCSE Chemistry (1CH0)](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-prepared-a-mixture-56ea73ab) · Published by Druglandscape Ltd.