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Cartesian Diver

​Lesson Objectives:
  1. Students will explore ideas of buoyancy and density.
  2. Students will experiment with different materials to discover what properties are necessary for a Cartesian diver.
  3. ​Students will use iterative design to create successful divers.
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Materials:

Let's Get Started!

Have the students fill their bottles to the brim with water. Challenge them to make an eye dropper go up and down in the capped bottle. The students will discover that they can accomplish this by partially filling the dropper before adding it to the bottle and then squeezing the bottle.

Next, challenge students to create divers using the materials provided. A variety of compressible materials can be used to create Cartesian divers. Cranberries, pieces of mushroom, and small marshmallows (though they disintegrate over time) are foods that work well. Non-food possibilities include Styrofoam, cork, and uninflated balloons. In addition, heavier materials are needed to provide weight, such as paper clips, pipe cleaners, and metal washers.
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Have students analyze their attempts to discern what properties are necessary for a successful Cartesian diver: the object must barely float (have a density slightly less than 1.0 g/ml) and must have a compressible part.
As an optional challenge, have students see if they can make a LEGO minifigure go up and down the bottle.