Create a festive fizzing Christmas shape with acids and alkalis!

You will need:

  • Plate
  • Spoon
  • Festive cookie cutter
  • Pipette (or teaspoon)
  • Bicarbonate of soda
  • Vinegar
  • Christmassy-coloured paint


  1. Place the cookie cutter on a plate. Spoon bicarbonate of soda into the shape, pressing each layer down as you go. Make sure you push plenty into the corners of your shape. You can use your teaspoon, the spoon handle or your fingers to press the bicarbonate of soda down.  
  2. Smooth off the top of your shape. Don’t worry if your shape isn’t full to the top.
  3. Add some festive paint to your shape to make it look Christmassy!
  4. Use your pipette or a teaspoon to drip vinegar onto the shape. Watch it bubble and fizz! Continue to add vinegar to your shape. What does the vinegar do to the painted parts and the white parts? Which fizzes the most? Have you managed to make any really big bubbles?      
  5. When you’ve had fun dripping vinegar onto your shape, see if you can lift off the cookie cutter. Your shape might be left behind or it might spread out. What colours has the paint gone – has it changed?


The Science Bit:

Vinegar is an acid, and bicarbonate of soda is an alkali. Acids and alkalis are opposites. When we combine acids and alkalis, a chemical reaction takes place with lots of fizzing and bubbling. The bubbles are carbon dioxide gas being given off. This reaction uses up heat, and so feels cold if you touch it. Reactions that get cold are called endothermic reactions. Endothermic means taking in all of the heat, and using it up, so the experiment feels cold.

Things to try:

Try the experiment using different cookie cutters. Does the size of the cutter make a difference? Add different paint colours, some glitter or some sprinkles to your shape to make it look even more festive.

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