An acid-base indicator is a substance that changes color as the pH of the solution changes. Indicators work because they are weak acids which when in solution, exist in equilibrium with their ...

Many chemicals can be classified as being acidic, neutral or alkaline by using indicators. The pH scale is used to measure acidity and alkalinity. When an acid is neutralised, it forms a salt.

Indicators are used to determine whether a solution is acidic or alkaline. Acids react with metals, bases and carbonates to produce salts. Neutralisation is the reaction between an acid and a base.