Indicators from plants
Crushed red rose petals can tell an acid from a base. So can purple cabbage.
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The idea
Many coloured plants make an indicator. Red rose petals, purple cabbage and hibiscus can all work.
To make one, crush fallen petals and soak them in hot water. Then filter the liquid to remove the bits. The coloured liquid left is an extract. Do not pick flowers off plants. An adult handles the hot water.
Step 1 of 4
- A rose extract. Its colours are not known yet.
- Add a known acid, lemon juice. It turns red.
- Add a known base, soap water. It turns green.
- Now its colours are known. Use it on unknown liquids.
Every indicator has its own colours. Red shows an acid with rose extract but a base with turmeric.