Finding acids with red cabbage

Teacher had a red cabbage in school with  her today.

It looks purple rather than red!

If you cut up a leaf and add very hot water the purple colour will start to run from the cabbage.

This red cabbage water is amazing!

It can help tell if something is an acid or an alkali (or neither).

We tried this out with some of our drinks.

We noticed the cabbage water turn pink or red with vinegar, lemon juice, orange juice, orange and pineapple juice, black current juice, and most surprisingly of all, with tea!

These are all acids and we will need to clean our teeth after drinking them.

Bread soda did not make the cabbage water turn red or pink.  Instead it made the cabbage water turn a bluey-green.

This is because bread soda is an alkali (and therefore good for cleaning!)

We wondered what would happen if we mixed an alkali with an acid.  What colour would the water turn?

We tried this and managed to get the water to turn back to the original cabbage water colour.

This means that when you mix and acid with an alkali the water becomes neutral again!

Such a fun investigation, and one that will help us mind our teeth!