Everyone loves stuff that changes color. It is magical, it is shocking, it is like a version of peek-a-boo that we don’t grow out of.
background: sure you could tell your kids you are just a magical witch and this is a potion you boiled up, or you can give them some background knowledge that will help them later in chemistry and biology!
Compounds that change color when they come in contact with other colors are called indicators-since they indicate, or let you know something is around! We are super lucky that one of the coolest indicators around, anthocyanin, can be found in red cabbage leaves. This indicator lets us know if substances are acids or bases by changing color! The word “acid” comes from the latin acidus, which meant “sour”, since we perceive the extra H+ ions acids release in water as sour on our tongues. Bases usually feel slippery and are usually found in soaps because of this property. A great way to spend sometime investigating chemicals around the house for acidic or basic properties is to boil up some cabbage juice and start observing the seemingly magic color changes when mixed with baking soda, lemon juice, ammonia, soap, milk…whatever you have around.
We wondered about grass, so we blended some to make it more liquid-y and easier to test, but the possibilities are endless and even one quarter of a head of cabbage provides enough juice to test literally everything you can thing of and more! Plastic pipettes make this even more fun, but pouring samples into bowls works too. Have kids predict what color will happen based on the sample’s observable properties beforehand. Try to make a rainbow of color changes by testing a whole range of pHs!
I love the colors of the boiled leaves and the juice itself. I ended up blending the used-up leaves into a lentil soup I was making that day anyways. The juice can be frozen for later experiments, or given away to neighbors who also have kids, who won’t judge you for dropping off kind of smelly jars of cabbage juice! It makes a lot, so get ready to share or freeze!
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cabbage juice pH indicator juice
Ingredients
- 1/4 head red cabbage
Instructions
- roughly chop the cabbage
- add to a large pot of water
- bring to boil - keep boiling until the water turns a deep purple
- spoon out the cabbage leaves and jar up the purple liquid