# Potassium bromide is an ionic compound with a giant lattice structure. When potassium bromide is melted, it conducts electricity, but in its solid state it does not. Explain why solid potassium bromide does not conduct electricity, and explain why molten potassium bromide does conduct electricity.

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

> Potassium bromide is an ionic compound. It has a high melting point of 734 °C.

## Mark scheme (4 marks)

1. In solid potassium bromide, the ions are held in fixed positions (in the giant lattice) by strong electrostatic forces
2. Because the ions cannot move, they cannot carry charge / current through the solid
3. When potassium bromide is melted, the strong electrostatic forces between the oppositely charged ions are overcome / broken down, and the ions become free to move
4. The free-moving ions carry charge through the liquid, so it conducts electricity

## 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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Source: [GradeNine](https://www.gradenine.co.uk/q/potassium-bromide-is-an-ionic-compound-90c76622) · Published by Druglandscape Ltd.