Is it possible to be acidic and healthy at the same time? This experiment uses a red cabbage to measure the pH value of the children’s exhaled breath. The experiment, which can also be done with eg foods, can form the basis for a discussion on health and science.

Teahing the activity
The ‘juice’ that is produced by boiling red cabbage has a nice blue colour and can be used as a pH indicator. The degree of acidity in lemons, soda water, vinegar etc can be determined by adding them to this red cabbage juice, which will change colour according to the degree of acidity. Red indicates acidic, blue indicates pH-neutral, and yellow indicates alkaline.

This experiment involves testing the children’s exhaled breath. As the children blow through straws into the juice, the CO2 in their exhaled breath gradually dissolves in the water. This forms carbonic acid (H2CO3 (aq)), which is the same as the carbonic acid in fizzy drinks. As mentioned above, the experiment can be extended to other foods and products.

See how the experiment is carried out in the step-by-step guide under Downloads.

Other activity suggestions
This experiment is part of Professor Jumpalot’s mission, which is a roleplay for children on nutrition and health.

Other similar experiments include ‘Sugar Water Tasting’ and ‘Sugar Stacking’.

Materials

• One fresh red cabbage
• Water, saucepan, knife, chopping board, strainer
• Large jar
• Large flask or alternatively a number of small clear plastic cups
• Straws

Educational goals
The red cabbage indicator shows a fun chemical effect that can be created with everyday items and would be a good starting point for a discussion on science.