Red Cabbage pH Indicator
Boil red cabbage to make a natural indicator that turns rainbow colours across acids and bases.
Start building ↓The build
Extract the dye
Steep chopped cabbage in hot water until deep purple.
Strain it
Pour off the purple liquid into cups.
Add test liquids
Drop different household liquids into each cup.
Read the colours
Acids turn it pink/red; bases turn it green/yellow.
Cabbage contains anthocyanin pigments that change molecular structure — and colour — depending on the surrounding hydrogen-ion concentration.
A closer look
The colour maps to pH: reds for acids, purple for neutral, greens and yellows for bases, giving a visual pH scale.
Variables to test
- 1 Build a colour chart and test mystery liquids.
- 2 Mix an acid and base — watch it shift to neutral.
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