# Aluminium oxide is an ionic compound with a giant lattice structure. It does not conduct electricity as a solid, but it does conduct electricity when it is melted. Explain why aluminium oxide behaves in these two different ways.

> Pearson Edexcel International GCSE Chemistry (4CH1) — 1.6 Ionic compounds · Explain · 4 marks

## Mark scheme (4 marks)

1. In the solid state, the ions are held in fixed positions (within the giant lattice) and cannot move
2. Because the ions cannot move, there are no charged particles free to carry charge / current
3. When melted (molten), the strong electrostatic forces between the oppositely charged ions are overcome / broken, so the ions are free to move
4. The free-moving ions carry charge through the molten liquid, allowing electrical conduction

## Key terms

- [ionic compound](https://www.gradenine.co.uk/glossary/ionic-compound)
- [giant lattice](https://www.gradenine.co.uk/glossary/giant-lattice)

## Related

- [Revision notes for Pearson Edexcel International GCSE Chemistry (4CH1)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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