Whether or not you like to eat red cabbage, you are going to love doing science with it by making your own red cabbage pH indicator. This is an amazing kitchen science experiment that turns solutions different colors as if by magic! Making a red cabbage indicator is a fantastic STEM activity to introduce children to acid/base chemistry.
Make a Red Cabbage pH Indicator
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Making a pH indicator from red cabbage is easier than might be expected. We headed to the kitchen to gather the following supplies:
- One half of a head of red cabbage
- Ice cube tray
- Tall clear cups
- Baking Soda
- Optional: More acidic/basic household items such as lemon juice, washing soda, cream of tartar, or antacids
After gathering our supplies we followed these simple directions to make the red cabbage pH indicator solution:
- Chop up the red cabbage into small pieces. Place 2-3 cups in a saucepan and cover with water.
- Bring the solution to a boil and then turn off the heat. Let it sit for about 30 minutes to cool down.
- Pour the cabbage water through a strainer into a jar or large measuring cup. The dark purple liquid in the jar is the pH indicator liquid.
- Pour the red cabbage indicator liquid into the compartments of an ice cube tray. Freeze for a couple of hours to make ice cubes. (Save some of this out for the fantastic color changing chemical reaction. It will get the kids SO excited about learning science!)
Red Cabbage Experiment
Once our cabbage ice cubes were frozen solid we followed these instructions to perform the actual pH science experiment:
- Fill one cup with water (this is neutral, or the control), one with vinegar (this is acidic), and one with a teaspoon of baking soda mixed with water (this is basic).
- Drop a couple of indicator ice cubes into each cup. Notice how the colors change in each one.
- Repeat with other acidic or basic household items in other cups. Try to guess what color the solution will be before dropping an ice cube in!
I was shocked at how fast the colors of our cabbage indicator changed and how delightfully beautiful the colors were! My three-year-old daughter was excited because the solutions turned into her three favorite colors: pink, purple, and blue.
This cabbage juice indicator experiment can be found in 50 Science Things to Make & Do, along with several other hands-on and kid-friendly science activities.
Red Cabbage pH Indicator: How it Works
Scientists use the pH scale to describe the concentration of hydrogen protons in a solution. A pH of 7 means that the solution is neutral. It is neither basic or acidic. A pH less than 7 means the solution is acidic while a pH greater than 7 means the solution is basic. The lower the pH, the more acidic a solution is.
Red cabbage contains a chemical called anthocyanin that changes color depending on the acidity of its environment. In an acidic environment it is reddish-pink, in a neutral environment it is purple, and in a basic (or alkaline) environment it turns bluish-green and even yellow.
This is a great way to introduce the concept of acids and bases to a child since they can see the color change before their very eyes.
We used these same scientific principles to create an amazing fizzy color changing chemical reaction and to dye Easter eggs naturally, which were both so much fun. Who knows, maybe doing all this chemistry with red cabbage will inspire the kids to eat it one of these days 🙂