Electrolyte

Summary: An ionic compound that conducts electricity when molten or dissolved in water because its ions are free to move. Tags: igcse chemistry definition electrolysis Created: 2026-07-14 Last Updated: 2026-07-14

An electrolyte is an ionic substance that conducts electricity when molten (liquid state) or dissolved in water (aqueous solution), because its ions become mobile and can carry charge through the liquid. Common electrolytes include molten lead(II) bromide, aqueous sodium chloride, and dilute sulfuric acid — all of which decompose chemically when a direct current is passed through them during electrolysis. Solid ionic compounds, such as sodium chloride crystals, cannot act as electrolytes because their ions are locked in a fixed giant ionic lattice and are not free to move. The conductivity of an electrolyte is due to the movement of both positive cations towards the cathode and negative anions towards the anode, completing the circuit in a fundamentally different way from the electron flow in metallic wires. For the IGCSE exam, it is essential to remember this critical distinction: a solid ionic compound does not conduct electricity, but once melted or dissolved it becomes an electrolyte and does.

Key term — IGCSE Chemistry (0620/0971) glossary.