Another exciting experiment involving balloons, this time we’re going to explore how heat can be used to blow up a balloon. How is this possible? Let’s find out with the Magic Balloon experiment. Perfect for kids and adults to do together as a fun science activity! You will need:
  • A clear plastic bottle
  • A balloon
  • A kettle
  • A medium sized tray
  • Water
  • An adult helper


  • Once you have gathered the required equipment, the first step is to take your kettle and fill it up with water. Turn it on and leave it to boil.
  • While waiting for the kettle, grab your plastic bottle and balloon. Give the balloon a quick stretch, remove the lid to the bottle and cover the mouth with the open end of the deflated balloon.
  • After that, prepare your medium sized tray and wait for the kettle to finish boiling. For this next part, it’s time to tag in your adult helper. They will need to fill your tray roughly halfway up with boiling water.
  • From there, try moving your bottle with the deflated balloon on top next to your tray of steaming water. Alternatively, your adult helper can place the bottle in the tray as long as their careful of the boiling water.
  • After a short amount of time, you should notice your balloon start to inflate by itself – remaining inflated for quite a while even if the tray of boiling water is taken away. But what’s causing it to inflate by itself? Let’s explore the science behind the Magic Balloon experiment.
The Science Bit: Almost as if magic, the balloon strapped onto the bottle starts to inflate when exposed to hot water. But why? Gases expand when they’re warm, including air. The hot water placed near the bottle heats up the air inside the bottle and the expanding gas blows up the balloon. This is because the particles inside the bottle start to move faster due to the heat and in turn, expand to fill the balloon. Likewise, if you were to place the bottle in cold water, the air would cool down and the balloon would shrink due to the particles slowing down.

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