// FIELD GUIDE 11 — LEVEL L3 (GCSE / NATIONAL 5)
Electrolysis: splitting compounds with electricity
Melt or dissolve an ionic compound and its ions are suddenly free to move. Add two electrodes and a current, and you can pull the compound apart into its elements.
// FIG. 01 — MOLTEN IONIC COMPOUND, LIVE
Orange cations (+) drift to the negative cathode; blue anions (−) drift to the positive anode. Each ion that reaches its electrode is discharged — it gains or loses electrons and turns back into a neutral atom or molecule.
// L3 — WHY IT NEEDS MOLTEN OR DISSOLVED
In a solid ionic lattice, the ions are locked in place — no current can flow. Melting the compound, or dissolving it in water, frees the ions to move, which is exactly what carrying an electric current requires.
// L3 — CATHODE AND ANODE
Cations (positive ions, usually metals or hydrogen) are attracted to the negative cathode, where they gain electrons — reduction. Anions (negative ions, usually non-metals) are attracted to the positive anode, where they lose electrons — oxidation. Electrolysing molten lead bromide, for example, deposits liquid lead at the cathode and releases bromine gas at the anode.
// L3 — WHERE IT'S USED
Electrolysis is how we extract very reactive metals (aluminium, sodium) that are too eager to bond to be displaced any other way, how we purify copper to near-100%, and how we electroplate objects with a thin layer of another metal.
// REFERENCES & FURTHER READING
Cross-check against your own exam board's specification (AQA, Edexcel, OCR, SQA).