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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