Cartesian Diver: Lab Activity
by Kenneth Fuller
© 2006

Review the meanings of the words, mass, volume, and density, since they are important in this activity.
Mass is _____________________________________________________________________________
Volume is ___________________________________________________________________________
Density is ___________________________________________________________________________

Materials needed:
    One three liter soda bottle, with label removed.
    One glass dropper.
    One beaker, deeper than the length of the dropper.
    A waterproof marker

    1.   Place marks, more or less evenly along the tube of the dropper. (fig. 1)fig. 1 dropper
    2.   Put water in the beaker until nearly full.        
    3.   Fill the dropper about half full with water.
    4.   Place the dropper in the beaker.
    5.   If the dropper sinks, take a drop of water out;             fig. 2 dropper
          If the dropper floats too high, add a drop of water.
    6.   Repeat steps 4 and 5 until the dropper just barely floats. (fig. 2)
    7.   Fill the soda bottle with water.
    8.   Place the dropper into the bottle without squeezing it.
    9.   Put the cap on the bottle.
    10. Squeeze the bottle gently, the diver should go to
           the bottom of the bottle.
    11. Release the bottle, and the diver should go to the top.
    12. Observe carefully as the diver goes up and down.
          What changes do you see?__________________________________________________________

    13. How do these changes effect the average density of the dropper and the air and water it contains?

    14. Does the hardness of your squeeze have any effect on the diver?
    15. Can you squeeze and hold just enough that the diver stops in the middle of the bottle?
    16. Empty the bottle, clean up your lab station, and return to your seat.