Kids can’t resist this amazing color changing chemical reaction. It fizzes, it changes color as if by magic, and it works over and over again. This experiment is completely nontoxic and made with common kitchen supplies. It is hands down one of our favorite kitchen science experiments to date.
After we completed our color changing chemical reaction my five-year-old said, “I want to be a chemist when I grow up!” and my three-year-old exclaimed, “I love science!” Those are some pretty sweet things for a science mama to hear.
Getting the Color Changing Chemical Reaction Ready
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We headed to the kitchen to gather these items:
- One half of a head of red cabbage
- Baking Soda
- Ice cube tray
- Tall clear cups
- Plastic Pipettes, if desired
First, we made pH indicator ice cubes. You will recognize these directions from another kitchen science experiment where we made our own pH indicator using red cabbage:
- 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.
- Mix the cabbage water with enough baking soda to turn the solution bluish-green. You will probably need a few tablespoons. There is no need to be exact.
- Pour this liquid into the compartments of an ice cube tray. Freeze for a couple of hours to make ice cubes.
Why does the red cabbage juice turn bluish-green when mixed with baking soda? Hint: Refer to my post about making a red cabbage pH indicator solution to find out!
Fizzy Color Changing Chemical Reaction Experiment
Once the ice cubes were frozen solid we followed these directions to create a fantastic fizzy color changing chemical reaction:
- Dump out the indicator ice cubes into a baking tray or casserole dish.
- Fill a cup with vinegar. Using a plastic pipette, squirt the ice cubes with vinegar and watch what happens. Do the ice cubes fizz? Do the ice cubes change colors?
- Now for the REALLY fun part. Place an indicator ice cube into a cup of vinegar. What happens? You may want to place your cup in the baking tray just in case it overflows! Add more ice cubes to your cup of vinegar. What color is the solution now?
The Science Behind the Color Changing Chemical Reaction
So, what is going on here? Well, a couple of things.
First, the fizzy part. This is a simple reaction between baking soda and vinegar. The old classic! Since the ice cubes contain baking soda they react with the vinegar in the glass to produce carbon dioxide bubbles: the fizz that you see and love.
Next, the color changing part. We started out with bluish-green ice cubes and ended up with bright pink vinegar. As we added more ice cubes the solution got darker and darker and eventually turned purple. It’s really cool!
The color changes because the pH changes. Scientists use pH to measure how acidic a solution is. Baking soda is basic, so the red cabbage juice turns bluish-green when mixed with it. Vinegar is acidic, which makes the red cabbage juice turn pink! As more baking soda is added to the vinegar the solution becomes more neutral, which is why it turns purple. Read my post about how a red cabbage pH indicator works for more details and more ways to experiment and play with red cabbage juice. We even dyed eggs with it this year!
I hope your kids and students love this experiment as much as we do! I had so much red cabbage juice that I made a whole bunch of indicator ice cubes to use on future rainy days when we are stuck inside. This experiment is so simple to do and so easy to clean up. It is exciting for the kids to see the fizz and the color change! It makes a dull afternoon at home exciting and educational.