Have you ever heard a coin that can dance?….. No…… well try this little easy experiment and you will have your coin use the magic of air pressure to dance the night away!


Glass bottle

coin that fits on bottle mouth

cup of water





Glass bottle may break when dropped. An adult should be helping you in this experiment.


Place the glass bottle into the freezer for 2-3 hours to get nice and cold.

Take out the bottle and place on the bench. Use the straw to get some water and place water onto the coin.


Turn the coin so that the wet side sits on top of the mouth of the bottle. The water helps the coin forma seal on the bottle.

Hold the sides of the bottle with your warms hands and wait. The dancing will start soon.

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  • detailed explanation of the science,
  • suggestions for modifications on this experiment,
  • how to set it up more scientifically (variables etc),
  • mini-challenges
  • perfect for homeschooling or those wanting to ‘Go All the Way!’

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This experiment looks at air pressure, how gases expand and contract due to changes in temperature, forces and more.

When you placed the bottle inside the freezer, the air inside the bottle cooled down. As the air molecules cool, they slow down and get closer together forming a  dense region of air (due to loosing energy). (picture A)


Wetting the coin and placing it on the mouth of the bottle forms a temporary seal on the bottle. When you hold the bottle, the warmth from your hands warms up the sides of the bottle (via conduction of heat) and eventually heats the air inside the bottle as well. The warmer air inside the bottle now expands (as it it getting more energy) and tries to move out of the bottle.

As the air expands it increases the pressure inside the bottle and every now and then the pressure is high enough to push  the coin up and the air escapes. (picture B)

The sound of the coin coming back down makes the ‘tapping’ noise that we say it is dancing!

This experiment looks at a variety of science concepts; heat transfer, pressure changes and sound.

Heat Transfer (conduction, convection and radiation)

Heat Transfer animation

Bitesize ‘Heat Transfer’

Pressure Changes

Particles in a gas

Heat loss: Here the heat is lost from the glass to the fridge and cools the bottle down. (The more molecules move, the higher the temperature and the slower they move the cooler the temperature)

Density: The amount of matter in an area is a measure of density. The cool air has a lower density as the molecules are closer together (due to traveling slower in cold environment).