Natural Indicator Experiment

Perform a first-hand investigation to prepare and test a natural indicator



  • To prepare a natural indictor:
    • Select a suitable coloured plant material, such as purple cabbage.
    • Extract the colour from the plant material by either:
      • Boiling it in water.
      • Crushing it with water or alcohol using a mortar and pestle.
    • Decant the solution from the solid.
  • To test a natural indicator:
    • Dip the ends of two strips of filter paper into the indicator and allow to dry.
    • Using an eyedropper, apply a drop of strong acid to one strip and a drop of strong base to the other strip.
    • Record any changes in colour.
    • Add additional drops of acid and base to the strips until no further changes in colour are observed.
  • If an indicator is prepared from purple cabbage, the following colours should be observed:
    • Initial/Neutral colour: Purple
    • Colour when exposed to strong acid: Pink, then red
    • Colour when exposed to strong base: Blue-green, then yellow
 

Purple cabbage

Easychem - Natural Indicator Experiment


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