You can make your own colour-changing potion just using vegetables! You will need a grown-up to do the cooking bit.

Making the potion:
Roughly chop half a red cabbage and boil in just enough water to cover it for around 10 minutes. The water should turn dark blue. Keep the water and put the drained cabbage to one side. Leave it to cool.

Doing the experiment: You need some beakers (see-through ones are best). Put about 100ml of water in each one and add 2 tablespoons of the blue potion. Now get experimenting! Try adding different things to see if you can make the liquid change colour, you’ll need to give them a stir. Things you could try: vinegar, lemon juice, milk, liquid hand soap, toothpaste, bicarbonate of soda, washing powder… anything else that you can find (check it’s safe!). Try it again using beetroot instead of cabbage, do you get the same results?

Think like a scientist:

  • Try to guess what colour each one will go before you do it.
  • Can you change the colour back if add something else?
  • Have a look at the cabbage, what colour is it? Would you want to eat it? How could you make cabbage stay red when it’s cooking? (look up red cabbage recipes for the answer!)
  • The colours change because the things that you are testing are called acids and alkalis. Acids turn the liquid red or pink, alkalis make it go blue or purple. Can you find out about them in books or online?