Making indicators

It is really easy to make your own indicators to show if a chemical is an acid, neutral or alkali. This experiment can be done without a Science lab, and can be adapted to be a sensory experience as well.

You will need:

beetroot, red cabbage and/or blackberries. Boiling water. A range of acids/alkalis to test.

To make the indicator, chop up your beetroot etc into small cubes. Add to boiling water and let stand until the colour has come out into the water.  Remove the lumps, preferably by filtering (practice those practical skills) and let the coloured liquid cool.

You can then add this to a range of acids/alkalis and look for the colour change. These work best if they are colourless and can include:

acid – lemon juice, vinegar, lemonade

alkali – bicarbonate of soda, glass cleaner

To make this a more sensory experience, encourage students to smell each of the chemicals that are being used. They can taste the acids, before they add a bit of their indicator to observe the colour change.

You can make all three indicators and then compare results, which do students think is the best? Can they think of any applications for this?


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