A Cartesian diver demonstrates the relationship between volume, mass and density.
A similar principle is used in Argo floats. cartesian_diver_exper.gif
What you need

  • Empty clear plastic drink bottle (1.5–2L size)
  • Eye Dropper – one made all of soft plastic (pipette) is easiest to use, but a glass one with a soft bulb would do
  • Modelling clay (such as plasticine)

What to do
Seal the Eye Dropper with a piece of modeling clay. Start with a ball of clay about 3cm in diameter (Shape the clay around the bottom of the dropper- making sure it is narrow enough to fit in the bottle!)
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Pipette with modelling clay

Fill the drink bottle with water.
Put the diver in – it should float at the top of the bottle.

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Cartesian Diver - only just floating at surface

Make sure the water in the bottle comes to the very top, and screw the top on tight.
Squeeze the sides of the bottle. The diver should sink.
Release the bottle. The diver should rise.
Try and get the diver to sit half way down.
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A Cartesian Diver

Get students to explain what they think makes the diver sink and rise. (Watching the bulb of the Eye Dropper as you squeeze the sides of the bottle should give a clue.)

How to make a squid-like Cartesian Diver

How about making a Cartesian Diver that looks like an Argo Float!
An Argo Cartesian Diver!