To observe how cabbage juice can test for acids and bases
- Red cabbage (small)
- Cooking pot
- Lemon juice
- Ammonia (Be careful with this—adult supervision needed!)
- Three clear plastic cups
Prior to the activity, prepare cabbage juice by placing cabbage leaves (eight to ten leaves) in a pot of boiling water. Water should just cover the leaves. Let boil until the water is deep purple. Place five or so drops of cabbage juice in each of the three cups. Then, put ten drops or so of the lemon juice in one cup, ten drops of ammonia in the second cup, and ten drops of vinegar in the third cup. Also do the same with water. Compare the results.
Substances such as lemon juice and vinegar turn the cabbage juice red because they are acidic. Ammonia turns the cabbage juice into a blue/green color because it is a base, a material that tastes bitter and makes an acid neutral. Water does nothing, as it is a neutral.