# A student burns magnesium ribbon in air. The magnesium reacts with oxygen gas from the air to form magnesium oxide. Explain why the mass of the solid in the reaction vessel increases, even though the law of conservation of mass states that mass is neither created nor destroyed.

> AQA GCSE Chemistry (8462) — 4.3.5 Use of amount of substance in relation to volumes of gases (Chem only) · Explain · 4 marks

> Magnesium burns brightly in air. The word equation for the reaction is: magnesium + oxygen → magnesium oxide.

## Mark scheme (4 marks)

1. No atoms are lost or made during a chemical reaction (conservation of mass)
2. Oxygen (gas) from the air is a reactant that joins with / combines with the magnesium
3. The mass of oxygen (gas) is added to the mass of the magnesium (solid)
4. The mass of the magnesium oxide product is greater than the mass of magnesium alone because the mass of the oxygen gas that reacted has been gained

## Key terms

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

## Related

- [Revision notes for AQA GCSE Chemistry (8462)](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-burns-magnesium-ribbon-in-c60adb5e) · Published by Druglandscape Ltd.