Indicator - GCSE Chemistry Definition

In GCSE Chemistry, an "indicator" is a special substance used to show if something is acidic or alkaline (also known as basic). It does this by changing colour when it is added to a solution. For example, litmus paper is a common indicator that turns red in an acidic solution and blue in an alkaline one. Indicators help chemists identify the pH level of substances, which tells them how acidic or alkaline something is. They are very useful in experiments where you need to know the exact pH level of a solution to understand its chemical properties.