Twinkl Education Blog
9 Mar '17

Easy Science Experiment - Red Cabbage Indicator

This is a guest post from Emma who blogs over at Adventures and Play.

British Science Week 2017 takes place between 10-19th March with events and activities taking place across the UK.This year's theme is “Change”. It is a chance to think about and investigate a range of changes - the seasons and climate, materials and energy. Twinkl has a wide range of scientific experiments that can be used at home and at school. We were intrigued by the Red Cabbage Indicator. The experiment didn’t need any preparation and used items that were easy to get hold of. The experiment also gave an instant result. We didn’t need to wait for days to see a change in the materials. The Red Cabbage Indicator certainly has a wow factor. The Red Cabbage Indicator is a way to find out whether a substance is acid or alkali. Red cabbage juice has an interesting property, a pigment called anthocyanin. It changes color depending on if it is exposed to an acid or an alkali. Cabbage juice is naturally neutral and is a purple colour. If an acid is poured into it, it will turn reddish. If an alkali is added, it turns blue or greenish. NB: cabbage water will stain so ensure children are adequately covered and supervised.

Materials needed for the Red Cabbage Indicator

* Red cabbage

* Knife

* Bowl

* Sieve

* Dropper or syringe

* Clear jars - we used small plastic test tubes from Flying Tiger

* Lemon juice

* Bicarbonate of Soda

* Water

Red Cabbage experiment

How to set up the Red Cabbage Indicator

1. Chop the red cabbage into small pieces. We only used one slice of red cabbage which was plenty for the experiment. With close supervision my son cut the red cabbage and placed the small pieces in a bowl.

INSERT PHOTO - CutRedCabbage

2. Pour boiling water over the red cabbage and allow time for the red cabbage to soften. The water will become dark purple. I obviously kept the boiling water out of reach of my son. We made predictions as to what would happen to the water.

Red cabbage water

3. Strain the cabbage water through a sieve and collect the purple water in a clear container. I did resort to using a funnel in order to get the water into the container.

Test Tube

4. Place a small amount of lemon juice, bicarbonate of soda and water into separate clear jars or small plastic test tubes. You will only need a small amount of each substance. With hindsight we used too much bicarbonate of soda.

Red Cabbage Indicator Experiment

Use a dropper or syringe to add a few drops of cabbage water into each of the test tubes. We added just cabbage water to the first test tube. This was to demonstrate what colour the original cabbage water was. Next we used a dropper to add cabbage water to the lemon juice. This instantly turned pink. We then added drops of cabbage water to the bicarbonate of soda. The combination turned the water a green colour. Finally, we added the cabbage water to the plain water. This created a lighter shade of purple.

Easy Science

It was very interesting observing the changes of the three substances, especially with the lemon juice. This experiment can be used across different age ranges. For older children it can be used as a recorded investigation whereas for younger children it would be great to use as part of a potions theme. Children could make their own colour changing potions inside clear containers!

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