Home Science: Make your own acid base indicator

Colourful indicators from flower petals at the House of Science. Photo: SUPPLIED

This week we conclude our home chemistry series with a lovely colourful experiment.

The background
Acid-base chemistry is all around us.

You may have created a 'volcano' with baking soda and vinegar or enjoyed eating sherbet fizz; both are acid-base reactions. Today we will make our own indicator that can show us whether a substance is an acid or a base.

The method
Chop or rip some red cabbage into very small pieces and place in a mug. Add hot water and stir for 10 minutes. Now strain the coloured liquid into another mug.

This purple liquid is your indicator. Place a tablespoon of your indicator in a series of small glasses. Add lemon juice or vinegar to one glass and record the colour. This colour indicates that a substance is acidic. Repeat using baking soda, this colour indicates a substance is basic.

The investigation
Test the acidity of several household items using your indicator.

Record your results in a chart. Black tea is also a good indicator -- does it have the same colour profile as the red cabbage indicator?

Thanks to the Science Award trust for this activity, it is part of the Matauranga Matu Kainga/Home Chemistry Badge. Happy investigating everyone.

- The House of Science Tauranga is a charitable trust which exists to connect and resource the local science community to enrich science education and increase the number and quality of students engaged in secondary school science. Contact Chris Duggan on (027) 337 9342 for any more information.