Teacher had a red cabbage in school with her.
In a way it was a fortune telling cabbage (It could tell whether things were acids or not). We know that acids are bad for our teeth and that we should wash our teeth well after eating or drinking acidic things.
We put a few leaves of the red cabbage into hot water and let it cool.
The cabbage water turned a light purple colour.
We filled lots of little cups with this cabbage water, and then added different liquids like vinegar, orange juice, lemon juice, bread soda, bleach, shampoo and conditioner. Each time the cabbage water was able to show us whether the liquid we added was an acid or a base/alkali.
We noticed that acids turned the cabbage water pink, alkalis (like bread soda) turned the cabbage water light blue and bleach takes all the colour from the cabbage water. We also found that if we mixed an acid (vinegar) with an alkali (bread soda) that we could get the colour back to the original colour in the control cup. This must mean that an acid and a base (alkali) can cancel each other out.
Having a red cabbage is a handy way to test for acids.
We might even try this at home with other liquids.