Fiducia TogetherAcids, bases and salts
The pH scale, neutralisation, and the reactions that make salts.
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
Acids release H⁺ ions in solution; alkalis release OH⁻. The pH scale runs 0 to 14, with 7 neutral. Neutralisation produces a salt and water.
Where it applies
GCSE chemistry and combined science, with a required practical on titration or on making a salt.
How it works
The standard reactions: acid + metal → salt + hydrogen; acid + metal oxide or hydroxide → salt + water; acid + carbonate → salt + water + carbon dioxide.
Strong acids fully ionise; weak acids partially ionise. Concentration and strength are different properties, and questions test the difference.
How to use it in your work
Learn the three general equations. Naming the salt correctly — the metal from the base, the ending from the acid — is a routine mark.
Strong versus concentrated is a guaranteed distinction question. Strength is about ionisation; concentration is about how much is dissolved.
A pH change of one unit is a tenfold change in H⁺ concentration.
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.