# A student heats a piece of magnesium ribbon in air. The magnesium glows brightly and a white powder is formed. The student tries to reverse the change but cannot get the magnesium back. Describe the evidence that shows this is a chemical change, and state one general difference between a chemical change and a physical change.

> Cambridge International IGCSE Chemistry (0620) — 6.1 Physical and chemical changes · Describe · 4 marks

> Magnesium ribbon is heated in air. It burns with a bright white flame and a white powder remains. The original magnesium cannot be recovered.

## Mark scheme (4 marks)

1. A new substance is formed (white powder / magnesium oxide)
2. The change is difficult / impossible to reverse (the original magnesium cannot be recovered)
3. Energy is given out / light and heat are released (bright glow indicates energy change)
4. In a physical change the substance is not changed / no new substance is formed, whereas in a chemical change a new substance is produced

## Key terms

- [chemical change](https://www.gradenine.co.uk/glossary/chemical-change)
- [physical change](https://www.gradenine.co.uk/glossary/physical-change)

## Related

- [Revision notes for Cambridge International IGCSE Chemistry (0620)](https://www.gradenine.co.uk/learn)
- [How to answer "Describe" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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Source: [GradeNine](https://www.gradenine.co.uk/q/a-student-heats-a-piece-of-23c17e07) · Published by Druglandscape Ltd.