litmus paper is an example of a... what?

Litmus paper is an example of an acid–base indicator (or simply, an indicator).

What litmus paper is

• Litmus paper is a special strip of paper treated with dyes from lichens that change color when dipped into solutions.

• It is used to distinguish acidic solutions from basic (alkaline) ones by observing a clear color change.

Why it is called an indicator

• An acid–base indicator is any substance that shows different colors in acidic and basic conditions, “indicating” the nature of the solution.

• Litmus paper does exactly this: blue litmus turns red in acid, and red litmus turns blue in base, so it serves as a simple visual indicator of pH.

Information gathered from public forums or data available on the internet and portrayed here.