With this simple red cabbage pH test, your kids will be amazed to find their homemade potions changing colour before their eyes!
Making colour changing cabbage juice is a really fun way to explore acids and bases. It’s a really colourful and exciting experiment, and great for a wide range of ages too.
Materials
Here’s everything you need to make colour changing cabbage juice:
- red cabbage
- access to equipment for boiling the cabbage and draining the juice
- clear containers
- liquids and solids to experiment with (see below)
Instructions
Here’s how to do this colour changing cabbage experiment at home.
1. Boil red cabbage for about 5 minutes and drain the juice. Keep the juice! An adult should heavily supervise or take care of this part themselves due to the very hot temperatures.
2. Set out several different transparent containers. Let your kids make their own ‘potions’ in these containers using different liquids. They can mix in solids too. Make sure the containers are no more than about half full.
Examples of what to make potions from:
- vinegar
- lemon juice
- water
- baking soda mixed with water
- laundry detergent
- any juices or fizzy drinks
- liquid hand soap
- other cleaning products (supervise very closely and wear gloves, follow instructions on the packaging)
- liquid/blended foods
***They can mix more than one of these together, but try to keep them separate at least for the first go – mixing them all up together too much might mean the acidic and alkaline substances neutralise each other, meaning you won’t get any exciting colour changes!***
3. Once the ‘potions’ are ready, add the cooled cabbage juice. You should notice the colours of the liquids change almost instantly!
Pink/red = the potion is acidic
Green/blue/yellow = alkaline
No change = neutral
How does this activity work?
Here’s a rundown on the science behind this fun activity!
Lots of substances are acids or bases. When a base can dissolve in water, it is called an alkali. Acids and bases are opposites. How acidic or alkaline something is can be measured on a scale from 0-14, with 0 being very acidic and 14 being very alkaline. The middle number, 7, means the substance is neutral – not acidic or alkaline.
Red cabbage contains a water-soluble pigment called anthocyanin that changes colour when it is mixed with an acid or a base. It acts as a pH indicator, which means it can tell you how acidic or alkaline something is. That’s why it changes colour when it comes into contact with acids or bases – and this causes your potions to change colour!
A HUGE thank you to STEM4Kids for sharing this awesome activity idea with us! You can find more STEM and STEAM activities by STEM4Kids here.
If your kids liked this activity, we think they’d love the colour-changing cabbage activity in our eBook ‘Fun at Home with SUPA STEM’. You can get a free copy here.
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