If you’re a Harry Potter fan you may want to try your hand at mixing up this color changing potion. Grab a head of red cabbage and a few items from the kitchen and you can cook up a potion that will change it’s color depending on what kinds of liquids you add to it.
What you need:
- Red Cabbage
- 5 clear cups
- boiling water
- an adult
- baking soda
- lemon juice
What to do:
- Finely chop up the cabbage until you have about 2 cups.
- Place the cabbage into a bowl and add enough boiling water to cover the cabbage.
- Let the cabbage soak for 15 minutes, until the water is red, purple, or blue. Now that you have your potion lets use it!
- Take the 5 cups and evenly distribute the cabbage juice between the cups.
- Number the cups with a marker 1-5.
- Add baking soda to cup 1 until you see a color change.
- Repeat with the lemon juice in cup 2, vinegar in cup 3, and antacids in cup 4.
- Leave cup 5 with just the cabbage juice.
- Compare the colors of the cabbage juice in all 5 cups. What do you notice?
What’s the Science?
This isn’t a potion at all. It’s science! Red cabbage 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 an 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 the cabbage juice? What color does the cabbage juice turn?