Litmus Paper - GCSE Chemistry Definition

Litmus paper is a type of special paper used in chemistry to test whether a substance is acidic or alkaline (basic). It is often used in experiments because it changes colour to show the pH level of a solution. When you dip blue litmus paper into an acid, it turns red, while red litmus paper will turn blue if it is placed in an alkaline solution. If there is no colour change, it means the solution is not strong enough to affect that litmus, not necessarily that the solution is neutral. For example, if red litmus stays red, the solution could still be acidic. If blue litmus stays blue, the solution could still be alkaline. Litmus paper is useful for quickly checking whether a solution is acidic or alkaline, but it doesn't give an exact pH — just a general idea.