Pigments are molecules that contain colour and the ones in red cabbage juice ( anthocyanin ) are pretty special. By adding a base or acid, we can both change their shape and their colour! The pigments are easy to collect and the basis for two easy home experiments: Colour Changing Magic Potions and Making Litmus Paper.

First, you will need to collect some magic molecules from a red cabbage: click here to find out how.

Materials

• Red cabbage juice
• 1 tsp baking soda
• 3 Tbsp white vinegar
• Clear glasses or bowls

Directions

1. Pour your prepared red cabbage juice into two clear glasses or small bowls.
2. Into one glass, stir 1 tsp of baking soda. Watch the solution turn blue – indicating that the pH has turned basic.
3. Into the second glass, stir 3 Tbsp of white vinegar. Watch the solution turn red/pink – indicating that the pH has turned acidic.
4. For fun, pour the glass containing vinegar into the glass containing baking soda and watch them foam! Tip: for less mess, pour both solutions into a big bowl!

You don’t need expensive chemistry kits containing dangerous chemicals to have fun doing science at home. This simple (and colourful) experiment will help you make you own litmus paper so that you can test acids and bases using simple household ingredients. You can also test these by making a colour changing magic potion!

First, you will need to collect some magic molecules from a red cabbage: click here to find out how.

Materials

• Red cabbage juice
• Paper towels
• Water
• Dishwashing Liquid
• Lemon juice
• Baking Soda
• Baking Powder
• Vinegar

Directions – Part 1

1. You will need your red cabbage juice (cooled and strained) and some paper towels. I folded mine twice to make thick squares.
2. Quickly dip / submerge the paper towels into the red cabbage juice. Don’t hold them under for too long as you want them to collect the colour pigments but not get so soggy that they fall apart. It’s a little like candle dipping – you may need to do a couple of dips to get a good colour.
3. Place the purple paper towels on a clean tray (that won’t stain) and put them somewhere warm (like the hot water cupboard) to dry until the next day.
4. You now have litmus paper! Cut them into strips for easy dipping.

Directions – Part 2

1. Using glasses or small bowls prepare the solutions that you want to test. Your litmus paper will stay purple in ph neutral solutions, turn red-pink in acidic solutions, and turn blue in basic solutions.
2. Dip away!

We used:

Bases: soapy water, baking soda, baking powder.

Acids: vinegar, lemon juice.

Don’t worry if your experiment doesn’t go perfectly (ours didn’t!); simply use it as a talking point to discuss why things didn’t turn out as expected. In our case, the detergent and baking powder didn’t dissolve properly which meant that out litmus paper stayed purple (recognising the ph neutral water). For more ideas on common acids and bases: click here.