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Grades 6–8 Beginner About 15 min Version 1 Awaiting review Free

Natural indicators: acids and bases

Some substances are acidic, some are basic and some are neutral. An indicator is a substance that changes colour depending on which of these it is mixed with. Red cabbage juice is a natural indicator. It is purple on its own.

What you will learn

  • Describe what an indicator is.
  • Use red cabbage indicator to identify acidic, basic and neutral substances.
  • Record observations as evidence for a conclusion.

Before you start

  • Know how to measure a liquid in millilitres (mL).

Materials

  • Red cabbage indicator
  • Lemon juice
  • Distilled water
  • Baking soda solution

Equipment

  • 3 beakers (50 mL)
  • Stirring rod

Procedure

  1. Add 10 mL of red cabbage indicator to each beaker.
  2. Add one test liquid to each beaker: lemon juice, distilled water or baking soda solution.
  3. Stir each beaker.
  4. Write down the colour you see in each beaker.

How this simulation is simplified

  • Colours are simplified to three groups. Real red cabbage indicator shows a range of colours from red to yellow-green.
  • Mixing is instant once you stir.