Educational Activity

Title: Squeeze me until I sink!

Prerequisite Knowledge:

Students should have prior knowledge and understanding of displacement.

Description:
If you take a close look at all of the wiring and cables connected to Jason II, you will notice that they are all filled with fluids. This exercise will help students understand why.

This is a simple, yet very effective teaching aid to demonstrate the compressibility of air (gasses) compared to water (liquids). In a closed bottle, a floating eye dropper will either float or sink depending on whether or not the bottle is squeezed or released. The eye dropper sinks because the small pocket of air in the eye dropper is compressed, demonstrating the compressibility of air compared to water.

Objectives:

During this exercise, students will:
o conduct an experiment using household products.
o investigate and evaluate the compressibility of gasses and liquids.
o create a hypothesis to explain experimental observations

Materials needed:

· 1 or 2 liter plastic soda bottle (empty with screw top)
· clear eye dropper
· water

Preparation before class:
The teacher/instructor needs to prepare the experiment before class. Do the following:

1. Be prepared for some spilling during preparation.
2. Fill water bottles to the brim.
3. Fill the eye dropper about 10-20% full of water. This should allow the dropper to still float when immersed in water with a visible "air bubble" at the top.
4. Gently place the eye dropper into the water filled bottle. The dropper should displace some of the water, which will spill over the sides. The dropper should float. If it sinks, then retrieve the dropper and decrease the amount of water inside of it.
5. Carefully, so as not to spill any more water, replace the cap on the bottle and firmly tighten it.
6. Test the water bottle by squeezing it. The eye dropper should begin to sink. Release the bottle to allow it to go back to its original shape. The eye dropper should begin to rise back to the surface.

Video Demonstration:

Sometimes it is hard to visualize what an exeriment is supposed do, so we have included a short 25 second demonstration video. For your convenience, we have included it in several formats. If you are not sure which format will work, simply click on a few and see which one will play in your browser.

Windows Streaming Video - Lower Quality [0.2mb]

Windows Streaming Video - Medium Quality [0.3mb]

Windows Streaming Video - Higher Quality [1.0mb]

MPEG - Lower Quality [2.0 mb]

MPEG - Medium Quality [2.2 mb]

MPEG - Higher Quality [5.2 mb]

AVI - Lower Quality [1.4 mb]

AVI - Higher Quality [3.7 mb]

Description:

1. Have students analyze the teaching aid. Ask them to write a series of observations about it. (ie. 2 liter bottle, full of water, no or very little air, eye dropper floating at the top, eye dropper is partially filled with water, and has air bubble at top, etc.)

2. Unlike many exercises, this exercise is best-done first and discussed/analyzed second. Therefore, ask the students to squeeze the bottle firmly so that their fingers "dent" the sides a bit. The eye dropper should begin to sink to the bottom of the bottle. (Provided that you tested this teaching aid before hand.)

3. Ask them to then release their grip. The bottles should spring back to their original shape, and the eye dropper should begin rising back to the surface.

4. Ask the students to analyze what is happening, and why squeezing the bottle affects the eye dropper. Depending on your students, you may need to give them hints such as taking a look at the air bubble in the eye dropper. In groups or individually, ask the students to write a hypothesis that might explain their observations.

5. Share and discuss the students' work.

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