Acids and Bases

Magic Purple Potion

Make your magic potion by chopping up half a red cabbage. Put it into a saucepan and cover it with water. Place the saucepan on the stove. Allow the water to boil for five minutes, then remove the saucepan from the stove and allow the cabbage and the liquid to cool. When it is cool, strain the liquid through a sieve. You can discard the cabbage (or eat it!), but keep the liquid.
Put a little of the potion into two small jars. Add a teaspoon of vinegar to one, and a teaspoon of baking soda (sodium bicarbonate) to the other.
What do you see?
The liquid changes colour!! The jar with the vinegar turns pink, and the jar with the baking soda turns green.

Why does the liquid change colour?

The liquid from the cabbage is called an indicator. It changes colour when it mixes with an acid or a base. You can test common liquids that you find at home by using your purple indicator potion. Vinegar is an acid, while baking soda is a base (or alkali). Try testing some of these substances, and record your results in a notebook:

Lemon juice
Salt
Yoghurt
Soap
Washing Soda
Black tea
Milk
Lime Juice
Cola
Toothpaste

You can try mixing acids and bases together. What do you see?

Return to start page

This page was designed and written by Alchemy Science Writing & Communication
Any comments? Contact us at: chidgey@mpx.com.au