The purpose of this lab is to gain an appreciation for the use of density as a means of physical separation of solutions or mixtures. This will be demonstrated through the use of antibubbles and samples of various plastics. This lab will also deal with the phenomenon of surface tension in relationship to antibubbles.

An antibubble is exactly what it sounds like, the opposite of a bubble. A normal bubble consists of a thin membrane of liquid with separating two layers of air, while an antibubble is a thin layer of air separating two layers of liquid. Because the antibubbles are composed almost entirely of liquid, their density is only slightly less than that of the solution they were made from, enabling them to be studied much longer than a regular air bubble would be. By varying the density of the liquids, either within the antibubble, or outside the antibubble, you will be able to alter its behavior. During the course of the experiment the students should carefully monitor the behavior of the antibubbles they create and attempt to link the observations to the density of both the antibubbles and the solution. The students will also look at the behavior of several samples of common plastics, and use a density gradient to determine the relative densities of the samples. After this experiment is completed the student will move to a second experiment examining the effect of surface tension. The students will observe what happens when the lab assistant sprinkles some lycopodium powder on the surface of water and see what happens when they reach into the beaker. The students will also see what happens when a drop of soap is added to the beaker.

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