Materials
-1 red cabbage
-Hot water
-Lemon juice
-Baking soda
-Optional fluids-window cleaner, vinegar, tonic water, lemon lime soda
Procedure
Put red cabbage leaves in a bowl and pour hot water over the leaves. Let the mixture stand for about 10 minutes. The liquid you will be left with will be bluish or purple in color. Pour some cabbage juice into a few clear glasses or beakers. Now, pour a little lemon juice into the first glass containing cabbage juice. The cabbage juice will turn a reddish-pink! now pour a mixture of baking soda and water into the second glass of cabbage juice. The cabbage juice will turn a greenish-yellow. Try pouring other liquids into the cabbage juice and see what colors show up...
What's Going On?
It turns out that red cabbage juice is sensitive to things that are acidic or the opposite-alkaline. Cabbage juice acts as an indicator, like ph paper, that changes color when it comes into contact with an acid or an alkali, (base). Red cabbage contains a pigment moleule called flavin. Flavin is an anthocyanin. Acidic solutions will turn the anthocyanin reddish-pink. Neutral solutions will allow the solution to remain purplish-blue. Basic solutions will change the color of the cabbage juice to a greenish-yellow. The color of the juice changes in response to changes in the hydrogen ion concentration. Acids will donate hydrogen ions while bases will accept hydrogen ions.
