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Emily Scioscia and Claire Jensen
 
I.                    Initial class hypothesis: smaller things move faster, so perhaps the smaller beads will move more quickly.
 
II.                  Summary of observations:
 
All measurements were taken at 40 x lens.
2 microns bead: moved 4um (4 units on ruler) away from starting point over one minute. We did this twice, and got the same distance both times.
4 microns bead: in one minute, it moved 70 units “down,” and approximately 20 units to the left of the ruler (it started “on” the ruler at 100) – but not only did it move “down,” it also went out of focus, which means it move up or out.
8 micron bead (courtesy of Paoli’s microscope set up): moved .5 (x2.5) microns in one minute.
 
*Because our initial data set for the 2 micron beads did not support our hypothesis, nor the matching trend that our 4 and 8 beads reflected, we decided to retest the 2 micron bead just incase…
 
Our results: this time, our 2 miceron bead moved 28 units, and became significantly out of focus.
 
III.                Conclusion: While our retesting of the 2 micron bead did not perfectly match up with the class’ initial hypothesis (that the small bead would move fastest), we can account for error in that we had no way of measuring how far “up” or “down” in the water the bead being watched moved. We also should consider that the heat of the light may have varied, depending on how long it had been on and how bright we had it.
 
IV.                Onions!
 
Thinking out loud/conclusions:
Ok. The salt makes the membranes of the cells shrivel/implode, seeming to suck something out. The water expands them back to their rounder, fuller, normal size. This seems to be caused by the cells absorbing the water. Water molecules are a little bigger than sodium molecules… Water doesn’t have a charge, but sodium has both a negative charge and a positive charge. A minimally possible thought (though judging by will’s behavior, we don’t think he thinks charge really matters in this):
 
Membrane is semi-permeable, and it is lipid-y. Water isn’t supposed to be able to permeate fatty membranes (ie oil in water), but eventually it does.. the fat and the water tend to separate… yet the water easily was being re-absorbed into the cells when water was added again after the salt had shrivled the membrane up (the membrane was within the cell wall…).
 
In the previous “beads” experiment with water, we hypothesized and for the most part, found to be true, that smaller molecules/things move faster. Since an NaCl (sodium) molecule is slightly smaller than an H2O molecule, we can hypothesize that the sodium moves faster than the water. This still doesn’t explain the effect of the salt on the membrane (zig-zaggy implosion) vs the effect of the water on the membrane (expansion/rounding out).  We are also attempting to relate the look of these lines (zig-zaggy vs. rounded out) with the initial experiment today: three beakers of water, one cold, one medium temp, and one hot--- each had blue dye added. The blue dye totally spread/evened out in the hot water beaker, and kind of froze/stayed in random swirls in the cold one. Temperature indicates amount of energy present (hot = more energy). The salt molecules had “zig-zaggy” lines like were stuck in the cold water—but moved around more like the molecules in the hot water….
 
???
 
No grant money for us. To be continued (maybe).