# Explain why a molten ionic compound conducts electricity but the same compound in its solid state does not.

> IB DP Chemistry Standard Level (2023 syllabus) — S2.1 The ionic model · Explain · 4 marks

> Ionic compounds such as potassium bromide (KBr) are used in various industrial electrolytic processes, but only when the compound is in the liquid (molten) state or dissolved in water.

## Mark scheme (4 marks)

1. In the solid state, ions are held in fixed positions within the lattice and cannot move freely.
2. Because the ions cannot move, there is no charge carrier available to carry an electric current in the solid state.
3. On melting, the regular lattice structure is disrupted/broken down, and the ions become free to move.
4. The freely moving cations and anions in the molten state act as mobile charge carriers, allowing an electric current to flow.

## Key terms

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

## Related

- [Revision notes for IB DP Chemistry Standard Level (2023 syllabus)](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/explain-why-a-molten-ionic-compound-66e7a036) · Published by Druglandscape Ltd.