Academy Curricular Exchange
Columbia Education Center 
Science


TITLE:  Non-Compressibility of Water

AUTHOR:  Michael Burgoyne, Rosamond, UT

GRADE LEVEL/SUBJECT:  (4-6)

OVERVIEW:  Students lack experiences that demonstrate
scientific principles. Many schools also lack the materials
needed to conduct meaningful experiments. This activity is
designed to give the students an experience with inexpensive
materials.

PURPOSE:  to have the students work on an experiment and
determine the principle involved.

OBJECTIVE(s):
1.   The student will understand that water cannot be
     compressed.
2.   The student will be able to explain the importance of
     this fact in his daily life.

RESOURCES/MATERIALS:  One two liter pop bottle for everyone
and one glass eyedropper. Eyedroppers can be obtained from
most drug stores. Plastic ones will work if you attach
enough paper clips to it to make it heavy enough. If this is
still too expensive you can demonstrate the experiment with
just one bottle and eyedropper. You will also need an area
where there is water available.

ACTIVITIES AND PROCEDURES:
1.   Each student will be asked to bring an empty two liter
     pop bottle. Have them wash and remove its label.
2.   The student will fill his pop bottle with water.
3.   The student will fill partially the eyedropper so that
     in a cup of water the eyedropper just barely floats
     below the surface.
4.   The student will place the eyedropper in the two liter
     bottle and screw on the lid.
5.   Have the students squeeze their bottle. When they do
     this the eyedropper will go down. Ask them to try and
     explain what happened.

TYING IT ALL TOGETHER:  After the students have formulated
some responses, question them as to why they thought that.
Have them squeeze slowly and watch the water level in the
eyedropper. As pressure is applied the water level in the
eyedropper goes up. The air is compressed and more water is
forced into the eyedropper making it heavier and causing it
to sink. Lead a discussion on this unusual property. Explain
that the science of hydraulics is based on this. Automobile
brakes are a good example of this. When you push on the
brake pedal in the car it pushes on a liquid which pushes on
a piston that activates the brakes.
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John Kurilecjmk@ofcn.org

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