Make your own pH indicator

David and Gabby Locke and the Entire Tech team receiving their Switched on Business Award from City of Armadale Mayor and Chairperson of the South East Regional Energy Group, Ruth Butterfield. They were joined by Cr Aaron Adams (City of Gosnells / SEREG delegate), City of Melville Business Development Advisor Stuart Tomlinson and Sustainability Engagement Officer Jess Sutherland. Photo credit: City of Melville. 

Some kitchen chemistry to help you determine the acidity of common household substances.

Chemistry doesn’t have to be dangerous or confined to a laboratory. Below is an experiment you can conduct in your kitchen to test whether common household substances are acidic, basic or neutral.

Red cabbage juice is a natural pH indicator. It will become purple to bright pink in acids and blue, yellow or green in bases.

You will need

  • Half a red cabbage
  • Chopping board and knife
  • Kettle (to boil water for the indicator)
  • Two large bowls
  • Strainer or colander
  • Five clear cups or jars

To test

  • Half a cup of lemon juice
  • One teaspoon of laundry powder
  • Half a cup of white vinegar
  • Half a cup of tap water
  • One teaspoon of bi-carb soda

Making your indicator:

  1.  Finely chop the red cabbage on the chopping board
  2. Place the chopped cabbage in a bowl 
  3. Boil the kettle and pour the hot water in the bowl until it just covers the cabbage
  4. Stir a little bit and then leave for five to ten minutes. The colouring you can see in the water is your indicator!
  5. Place the strainer over the second large bowl and pour off the liquid
  6. Throw your cabbage in the compost
  7. Your indicator is now safely in your bowl

Testing your chemicals

  1. Label your cups 
  2. Half fill cup with the test chemicals. Dissolve the laundry powder and bi-carb soda in a half a cup of water to make your solutions
  3. Add a teaspoon of indicator to each cup and observe the changes in colour. See table below to determine the approximate pH of your substances

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