# Magnesium reacts with oxygen to form magnesium oxide. Explain why the mass of magnesium oxide produced is greater than the mass of magnesium used in the reaction.

> Edexcel GCSE Chemistry (1CH0) — 1.8 Calculations involving masses · Explain · 4 marks

> A student burns a strip of magnesium ribbon in air and notices that the white powder formed has a greater mass than the original magnesium ribbon.

## Mark scheme (4 marks)

1. Magnesium atoms react with / combine with oxygen atoms (from the air)
2. Atoms are not created or destroyed in a chemical reaction (conservation of mass / atoms)
3. The magnesium oxide contains both magnesium atoms AND oxygen atoms
4. So the mass of the product (magnesium oxide) equals the mass of magnesium PLUS the mass of oxygen that reacted

## Key terms

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

## 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)
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Source: [GradeNine](https://www.gradenine.co.uk/q/magnesium-reacts-with-oxygen-to-form-42d23c28) · Published by Druglandscape Ltd.