Learn: Using Litmus to Identify Acids and Alkalis

Welcome!Today, we’re exploring how to identify acids and alkalis using litmus paper. This is a key skill in chemistry, and by the end of this lesson, you’ll feel confident recognising acids and alkalis easily!

What is litmus paper?Litmus paper is a simple indicator used to test whether a substance is acidic or alkaline. It comes in two types: red litmus and blue litmus paper.

How does litmus paper work?Litmus paper changes colour depending on the pH of a substance:Red litmus paper turns blue when exposed to an alkali.Blue litmus paper turns red when exposed to an acid.It stays the same colour if the substance is neutral.

What are acids and alkalis?An acid is a substance that releases hydrogen ions (H+) when dissolved in water. Acids have a pH less than 7. An alkali is a type of base that releases hydroxide ions (OH−) in water, with a pH greater than 7.

How to test for acids and alkalis?To test for acids or alkalis using litmus paper:Dip red or blue litmus paper into the substance you want to test.Observe if the colour changes.Red litmus paper stays red in acid but turns blue in alkali. Blue litmus paper stays blue in alkali but turns red in acid.

Why is litmus paper useful?Litmus paper is a quick and simple way to identify whether a substance is acidic, alkaline, or neutral. It is widely used in laboratories and experiments to test pH levels without needing complex equipment.

Review Time!Great work! You’ve learned all about using litmus paper to identify acids and alkalis. Now let’s test your understanding with a few questions!