In the laboratory, chemists use ready-made test sticks (pH indicators) that can change color to examine whether a liquid is acidic. Unfortunately, we don’t have anything like that at home. But we can make our own test tool with red cabbage juice. How does red cabbage juice change color when it comes into contact with liquids of different acidity?
Red cabbage and blue cabbage – what do they have to do with chemistry?
You will need
- Approximately 200 g fresh red cabbage
- Pot or bowl
- Measuring cup
- Cutting board and knife
- Empty jam jars
- Tap water
- “Test liquids”: dishwashing liquid, citric acid solution*, aqueous solution of baking soda*, distilled water*)
Let’s get started!
1. Weigh red cabbage and cut into small pieces
Weigh 160 g of red cabbage and carefully cut it into small pieces.
2. Infuse in water
Pour the chopped red cabbage into a pot or bowl, add 250 ml of water and let everything steep together for about 15 minutes.
Separate the leaves from the juice using a sieve. Pour the juice into a bottle (e.g., old olive oil bottle). Now you can use the red cabbage indicator.
4. Use the juice as pH indicator
Now you can test which colors the red cabbage juice can take on. You need a separate glass for each liquid you want to examine.
Place a piece of paper in front of each jar and number the pieces of paper from 1 to 5. Make up liquids that you can test. For example:
50 ml tap water + 50 ml citric acid.
90 ml tap water + 10 ml dishwashing liquid
100 ml distilled water
100 ml tap water
100 ml tap water + 1 teaspoon baking soda