Year 7 have taken part in a really cool (if not rather pongy!) experiment in their recent Chemistry lessons. They made their own indicator fluid out of red cabbage leaves, simply by extracting the fluid.

The lesson was part of their studies into the pH scale and reinforced the idea that substances can be classified as either an acid or a base, acids having a low pH and bases being at the opposite end of the scale with a high pH. Scientists use an indicator to assess where in the pH scale a substance sits.

Purple cabbage juice can be used as a home-made indicator fluid as it contains a water-soluble pigment called anthocyanin. This pigment changes colour when mixed with substances that are either or acidic or alkaline (basic).

The students were provided with a coloured pH scale that related to their cabbage fluid indicator. They added drops of the substances they were testing to their home-made indicator and compared the resulting colour to the pH scale provided. They were then able to use this information to assess the pH of the substance under test.

Senior School | 15/03/2021