Add baking soda to cabbage juice and what color will it turn: Blue or pink? What about cola or vinegar? This experiment is fun for any age, but is best understood by older kids. My youngest son was fascinated with the color changes while my older son was able to figure out the common link between the additions to the cabbage juice and the color change.
Common sense warning: Using a grater can be tricky, so please check with an adult before shredding the cabbage.
What you need:
Red cabbage
2 bowls
Grater
Strainer
Clear cups
Baking soda
Liquids to test: Lemon juice, cola, orange juice, vinegar, laundry detergent
What you do:
Grate about 1/2 of a head of red cabbage into a bowl.
Cover the cabbage with cold water for 30 minutes to 1 hour.
Pour the cabbage and water mixture through a strainer into another bowl to capture the purple juice.
Pour your juice into at least 4 different cups.
Add 1 teaspoon baking soda to all but one of your cups of cabbage juice. Did the juice turn blue?
The cup without the baking soda is your “control” cup. You want the other cups to match this one.
Now add one teaspoon of a test liquid at a time to a cup of blue liquid. Can you change the colors to match the purple control?
Try all of your test liquids and see how close you can come.
Why does it work?
Red cabbage juice contains a pigment molecule called flavin that changes color when an acidic liquid is added to it. Flavin is also found in apple skins, plums, poppies, cornflowers, and grapes. Adding baking soda to the cabbage juice makes it a neutral base. When you add liquids to the cabbage juice, very acidic solutions will turn it a red color; neutral liquids make a purplish color; and basic solutions will make cabbage juice a greenish-yellow.
