Colour Changing Cabbage

Ahh Stinky, Smelly, Science! In this easy kitchen experiment we make a indicator solution using the juice of a red cabbage, or is it blue, or pink...wait now its red! Get ready for some colour changing fun.

What You Need:

  • Red Cabbage

  • Water

  • Blender

  • Strainer

  • Household chemicals/ingredients to test

Transparent liquids give the most impressive results. We used:

  • Cloudy Ammonia
  • Baking Soda
  • Egg Whites
  • Sugar Solution
  • Hand Sanitiser
  • Soda Water
  • Lemonade
  • Vinegar
  • Lemon Juice

What You Do:

  1. Pull off 3 or 4 cabbage leaves and put them in a blender with around a cup of water.

  2. Blend the cabbage until smooth.

  3. Strain the cabbage juice using a sieve. If the solution is too dark you might want to add a bit of water to dilute it so the colour changes are more obvious.

  4. Experiment by adding the different ingredients.

How It Works:

Red cabbage contains a pigment called anthocyanin that changes colour when it is mixed with an acid or a base.

Substances are classified on a pH scale (0-14) as either an acid (low pH), neutral (pH of 7) or a base (high pH). Scientists can tell if a substance is an acid or a base by using an indicator. An indicator is usually a chemical that changes colour if it comes in contact with an acid or a base.

In our experiment, the purple cabbage juice is an indicator. It turns red when it mixes with something acidic (e.g. lemon juice, vinegar) and turns green/blue when it mixes with something basic (e.g. baking soda, ammonia).

What Next?

You can try to make your own pH indicator strips, like what they use to test pool water. Soak some coffee filter paper in concentrated cabbage juice and leave it to dry. Cut it into thin strips and try dipping it into different solutions to test their pH.