Color Changing Potion

What you need:

Red cabbage
Bowl
Marker
5 clear cups
Knife
Boiling water
Baking Soda
Lemon Juice
Vinegar
Antacids

What to do:

With adult help, finely chop 2 cups of cabbage.
Place the cabbage into a bowl and add enough boiling water to cover it. Let the cabbage soak for 15 minutes, until the water is red, purple or blue.
Number the cups between 1-5 and evenly distribute the cabbage juice between them.
Add baking soda to Cup 1 until you see the color change.
Add lemon juice to Cup 2, vinegar to Cup 3 and antacids to Cup 4. Leave Cup 5 with just the cabbage juice.
Compare the colors of the liquid in all 5 cups.

What’s the science?

Red cabbage juice contains the pigment flavin. This pigment is in the juice that leaks into the boiling water. Flavin will change color in response to changes in the hydrogen ion concentration, this is commonly called the pH of a solution. Acids have a lower pH (0-7) and bases have a higher pH (7-14). Acids will change the color of the cabbage juice to a deep red. Bases will change it to a greenish-yellow. Something that has a pH of 7 is said to be pH neutral because it is not an acid or a base.

The cabbage juice is called in indicator because it can tell you the pH of a solution based on the color that it changes. The vinegar will turn the cabbage juice red because it is an acid (acetic acid). The baking soda will turn the cabbage juice greenish-yellow because it is a base (sodium bicarbonate).

What color does the cabbage juice turn when you add the other household items?
What else could you add to cabbage juice?
What color does the cabbage juice turn?

Supplemental Materials:

Christmann, E. (2005) Testing the pH level of soft drinks. Science Scope, Vol. 28, No. 8, 54-55.

Standard Alignment:

Ohio, Physical Sciences, 3-5, A

Michigan, Matter and Energy, Middle, IV.1