This is a fun way to test the acidity of everyday materials by using cabbage.  The more I learn about plants, the more I see they hold the solutions to many of our problems—plants rock!  This experiment is from The Curious Boy’s Book of Exploration by Sam Martin, a book packed with entertaining challenges, puzzles, experiments, tricks and riddles (a red house is made of red bricks, a yellow house is made of yellow bricks, what’s a greenhouse made of?     glass!!!)

Some of the earliest experiments on acids and bases arose when farmers noticed that cabbages grew red in some soils, but purple or blue in others.  Chemists later discovered that cabbage juice contains a pigments which changes color at different pH levels.  Acidic substances will turn the cabbage juice red, neutral items will be purple and basic or alkaline will be greenish yellow.  Use the following color scale to test some everyday items around the house for their acidity.
pH (low number is acidic)
2 red
4 purple
6 violet
8 blue
10 blue/green
12 yellow/green

Steps
1. Boil 2 cups water
2. Finely chop half a head of red cabbage and pour boiling water over it. Let it stand for 10 minutes. The liquid should be a purplish/blue color (neutral). This is your indicator.
3. Pour this liquid (strain out all the cabbage pieces) into small bowls. Add a small amount of household items to each bowl and watch how the color of the liquid changes. Them match to the above scale to learn the acidity level.
4. Try things like lemon juice, baking soda, soap, ammonia and of course some soil from your garden.
5. Acids and bases also react together and cancel each other out. Try mixing a little of each type of indicator liquid and watch the solution slowly change back to neutral.

Have fun!