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Phase 1: In search of Brownian Motion we observed plastic beads of three sizes (2, 4, and 8 microns respectively) for two minutes under 40X power. We completed three trials for the 2 micron beads and two trials for the 4 and 8 mircon beads. The average movement is represented below:

2 micron beads: about 7.67 microns.

4 micron beads: about 5.625 microns

8 micron beads: about 2.5 microns.

It should be noted that, during our calculations, we omitted a fourth trial of the 2 micron beads as we determined it was not representative of the general motion of the beads (during this trial a bead was observed to move 75 microns. Though this would have further proved Brownian Motion, the finding was an outlier).

Phase 2: During this portion of the lab we observed the changes in an onion cell when is was immersed in .1% salt water, 25% salt water, and distilled water. It was observed unanimously that the cell membrane of the onion cell shrunk away from the cell wall when immersed in 25% salt water. This pattern points to a very NON-random movement of molecules (which contradicts the earlier findings of the lab). However, in the same way that temperature seems to influence the movement of molecules, the concentration of a particular solute can dictate how a group of molecules will move. In this case, the salt concentration gradient over the cell membrane (less salt in the cell, more salt outside of the cell) caused the water to move out of the cell so as to maintain equilibrium (as the cell membrane was impermeable to salt) - that is, the water left the cell so that the water to salt ratio was equal inside and outside of the cell. In this case, equilibrium seemed to take precedence over random movement.

One way to test this theory of equilibrium influencing the random movement of water molecules would be to use a dialysis bag manufactured to be impermeable to molecules larger than water. By filling a dialysis bag impermeable to glucose with water, and placing it into a solution including glucose, we could observe the movement of water by taking a measurement of the weight of the bag before and after exposure. This experiment would establish whether movement of water molecules could/would be directionally dictated by a solute concentration gradient over a membrane.

This process of equilibrium, like evolution (discussed in class today) is a blind process, devoid of intention.

Julia Stuart and David Richardson