Cartesian Science Fair Project

The Cartesian science fair project is one of the oldest and most traditional science experiments around. This experiment is based on the discoveries of Rene Descartes who discovered you can make an object dive and surface in a closed container using the ideal gas law and Archimedes' principal, also referred to as the principals of buoyancy.

Below are the instructions for using this historical science experiment for a cartesian science fair project.

The Cartesian Diver

Materials

Instructions

Fill your bottle with water. Also fill the eye dropper about 3/4 full of water. Drop the eye dropper in the water. It should float to the top of the water, but most of the dropper should still be submerged under the water. You will need to adjust the water content to make it float just enough to keep it at the top of the bottle.

Replace the screw on cap and tighten it. The container needs to be air tight.

Squeeze the bottle slightly to make the diver sink. Release the bottle to make the diver resurface.

As you can see this is a very simple experiment. The diver dives because when you squeeze the bottle you change the liquid pressure inside the bottle and according to the ideal gas law, the pressure forces the liquid to find an area with lower pressure, which is inside the eyedropper. When more pressure is put on the air bubbles in the eye dropper teh air bubble shrinks as it is compressed. This makes more space for water in the dropper, which in turn causes the eye dropper to sink.

If you are interested in expanding on this experiment you will need to use your imagination. First of all you will need to identify the variables in this experiment. They are the liquid inside the bottle and the diver. One variation on this experiment is to use a liquid other than water to test out the Cartesian principal. Another variation is to heat the water to increase the pressure inside the bottle. Are you able to make the diver dive and surface by applying and removing a heat source as opposed to squeezing the bottle?

Since this is a classic science experiment you cannot use it for a science fair project. However, you can use the principals and science concepts that you learned from this experiment to design a unique project. For example, you can use this principal to design a timer or you can find some other fun way to apply this experiment to another task.

By the way, did you know that this is one of many free science fair physics that is on the www.super-science-fair-projects.com website?