Fiducia TogetherElectrolysis
Splitting compounds with electricity. What goes where, and why.
Please note: This page explains a word or a process in education. It is general information about the system, the law and the guidance in England — not advice about your child, your school or your exam. If a decision is going against you, get advice from one of the free services we link to before you agree to anything or miss a deadline. If you are revising, check your own exam board's specification: boards word things differently and yours is the one that marks you.
What it is
Electrolysis uses an electric current to break down an ionic compound that is molten or in solution. Positive ions move to the cathode; negative ions to the anode.
Where it applies
GCSE chemistry and combined science, with a required practical.
How it works
Cations go to the cathode and gain electrons — reduction. Anions go to the anode and lose electrons — oxidation.
In aqueous solution water competes: hydrogen is produced at the cathode unless the metal is less reactive than hydrogen, and oxygen at the anode unless a halide is present.
How to use it in your work
Learn the mnemonic that works for you, but be able to say WHY: positive ions are attracted to the negative electrode.
Half equations must balance for charge as well as atoms. Show the electrons.
For aqueous solutions, apply the reactivity rule explicitly rather than guessing the products.
Where to get help
Your teacher, your board's specification for the depth required at your tier, and Bitesize for the diagrams.
Revise this with a song
These are ours. We write revision songs because a lot of people remember a tune when they cannot remember a page, and because revising out loud in the kitchen beats staring at a highlighter.
- The Chemistry Song The GCSE chemistry specification, set to music.
Where to read more
Last reviewed 2026-08-28 by Fiducia Together · Next review due 2027-08-28
Please note: This page explains a word or a process in education. It is general information about the system, the law and the guidance in England — not advice about your child, your school or your exam. If a decision is going against you, get advice from one of the free services we link to before you agree to anything or miss a deadline. If you are revising, check your own exam board's specification: boards word things differently and yours is the one that marks you.