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Red-cabbage rainbow

A natural indicator shows a different colour at every pH.

Topic: Acids, bases and saltsGrade: 9Free

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What you do

  1. Add acid to one tube.
  2. Add a base to another tube.
  3. Make a third colour with sodium carbonate.
  4. Turn on the pH meter and order the tubes from acidic to basic.

More experiments on this topic

Neutralisation with an indicatorTurn a pink base colourless by adding acid, and watch the temperature rise.Strong and weak acidsSame concentration, very different behaviour.Making a salt: copper sulfateBase + acid → salt + water, with copper(II) oxide.The hydrogen balloonCollect the gas from a metal and an acid in a balloon — then light it.pH titration curveAdd acid from a burette and draw the S-shaped curve.Making a salt: copper(II) sulfate crystalsReact an insoluble base with an acid, filter off the excess and crystallise the salt.