more dates coming soon!

Floating & Sinking Cans

Don’t let your soft drink choice get you down in this heavy activity

Australian Curriculum links

  • Science > Chemical Sciences > Year 4 > ACSSU074

You’ll need

  • One large clear container of water (a small fish tank works well)
  • One can of diet soft drink
  • One can of non-diet soft drink

What to do

  1. Fill the container three quarters full of water.
  2. Lower the can of non-diet soft drink gently into the container of water and let it go. Does it float or sink?
  3. Now lower the can of diet soft drink into the container. Does it float or sink?

What’s happening?

The two cans of soft drink have different densities due to the different amounts of dissolved sugar in the liquids they contain. The more dissolved sugar, the more dense the liquid.

The can of non-diet soft drink has a high concentration of dissolved sugar, so it sinks lower as it is denser. A single can of Coke contains around 40g of sugar (or 10 teaspoons)!

The can of diet soft drink doesn’t contain any sugar - it contains a small amount of concentrated artificial sweetener instead. So the density of the diet soft drink is much closer to that of pure water, making it float higher in the jug.

Real world links

Dissolved salts in sea water make it denser than freshwater. This means that fresh water floats on top of salt water.

Differences in salt levels and water temperatures of different bodies of ocean water can be responsible for large-scale ocean currents due to the different densities. You can learn more about these currents by researching the term ‘thermohaline circulation’, in which ‘thermo’ refers to temperature, and ‘haline’ refers to salt.