Lesson 2 of 7

Indicators

Goal: Use indicators to identify acids and alkalis.

Puzzles for this lesson

Word search0 of 8 foundCrossword0 of 38 letters

An indicator changes colour to show whether a liquid is an acid or an alkali.

Two beakers, one with a red strip of paper and one with a blue strip
Litmus has two colours. It is red in an acid and blue in an alkali.
Seven test tubes of liquid in rainbow order from red to purple
Universal indicator has many colours. It shows how strong the acid or alkali is.
  • Red or orange means acid. Blue or purple means alkali.
  • Green means neutral: neither acid nor alkali. Pure water is neutral.

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Key words in this lesson

Acid Has a pH below 7

Alkali Has a pH above 7

Neutral pH 7, neither acid nor alkali

Indicator Changes colour in acids and alkalis

Litmus Red in acid, blue in alkali

Universal indicator Shows a range of colours for pH

For teachers: AQA 3.6.2 · Pearson Edexcel 24.2 · Cambridge 7Cp.03