Fizzing Witch's Brew

Baking soda being spooned into a bottle of blue foaming liquid
"Witch's Brew" by Paul Swift

Did you know that by mixing the right things together you can make thousands of bubbles appear from seemingly nowhere? In this popular experiment we brew a pretend witch's potion!

Experiment

  1. Line a tray with kitchen paper and use this to contain mess.
  2. Carefully pour vinegar into each bottle, up to about a quarter full.
  3. In each bottle add some glitter or glitter stars and some food colouring.
  4. Put a squeeze (a teaspoon's worth or two) or washing up liquid into each bottle.
  5. Put the bottle caps on and give each bottle a good swirl to mix the ingredients. Swirl rather than shake so that it doesn't bubble up too soon!
  6. Take the bottle caps off and remove them from the experiment area. Don't place them back on after the next step.
  7. Spoon some baking soda powder into each bottle. What happens?

So what's happening?

When baking soda (bicarbonate of soda, a base) and vinegar (acetic acid) mix together a chemical reaction begins, and one of the products of that reaction is the same gas that we also breathe out, carbon dioxide. This is where the bubbles come from, and because the mixture includes washing up liquid these bubbles of gas become trapped in thin films of water and the result is our sparkly foam!

What if?

What would happen if you:

  • Used salt or sugar instead of bicarbonate of soda?
  • Used lemon juice instead of vinegar?
  • Didn't add washing up liquid to the mix?