Updated: Feb 21, 2021
Learn about acids and bases by making a pH Indicator from red cabbage, just like this one from the Royal Institution, then use the rest of the cabbage to make a tasty slaw that goes well with with sausages.
Indicator: red cabbage, hot water, vinegar/lemon juice, bicarbonate of soda, three glasses/bowlsSlaw: red cabbage, mayonnaise, vinegar/lemon juice, salt, optional: carrot, apple, dijon/wholegrain mustard
1. Make the indicator
Roughly chop about a quarter of the cabbage
Add it to a jug of hot water and stir
2. Prepare your supper
Cook the sausages under the grill
Shred about half the red cabbage
If using, finely slice an apple and grate (or julienne) a carrot
In a bowl, combine approximately 10 tbsp of mayonnaise with 2 tbsp vinegar/lemon juice and 1 tbsp mustard (if using)
Mix well, add the chopped cabbage, apple/carrot if using, season to taste
3. Do some science
Fill three glasses/bowls half full with the purple cabbage water
To one, add some vinegar or lemon juice – see the colour change
To another, add some bicarbonate of soda
Compare these colours to the original
4. Serve your supper
Check the sausages are piping hot in the middle
Serve with the cabbage slaw
What’s going on? The science in a sentence… A chemical in the cabbage, called anthocyanin, changes colour depending on whether it’s mixed with an acid (like vinegar) or a base (like bicarbonate of soda).
Why is this important for our daily lives?
As well as helping us make yummy cakes and livening up fish & chips, bicarbonate of soda and vinegar can be used for cleaning all sorts of things around the house. In industry, acids and bases are used for many processes. For example, acid is used in batteries and the production of circuit boards. Indicators help us know how acidic something is. The level of acidity is important in nature, for example, our bodies constantly balance acidity levels in our blood to stay alive and oceans becoming more acidic is bad news for marine life.
Other ideas for supper… This cabbage slaw also goes well with grilled halloumi slices, chicken drumsticks, fish fingers or on top of a burger. In winter, you might prefer to cook the cabbage - check out this super-easy microwave red cabbage recipe or go gourmet with this festive recipe from BBC Good Food.
And finally…. Try using your cabbage indicator to test other things to find out if they are acids or bases - try lemon juice, egg, washing-up liquid, cola, fruit juice, coffee, toothpaste and soap. Can you make a rainbow like this school science club did? What happens if you add acids and bases together? Can you make the cabbage indicator go back to it’s original colour? You can also freeze your indicator liquid into ice cubes like The Science Kiddo. For older kids, check out this brilliant video from BBC Earth Lab where Jon the science rapper, uses cabbage indicator to test some household chemicals.