Red cabbage juice can be used as an indicator to test if a liquid is an acid or a base.

If added to a base it will turn blue or green and if added to an acid it will turn red. To make the cabbage juice, cut up a leaf of red cabbage into small pieces and blend with some water until it’s liquified. Then pour through a strainer to separate the juice from the pulp. Now the juice is ready. We added about a tablespoon of cabbage juice to the following: baking soda, sugar solution, water, vinegar and lemon juice. Notice how the colors move from blue to red. So cool!