Replicating a Scientific Experiment

Since I was in my molecules and atoms period, I also tried doing this experiment: Measuring the Diameter of a Molecule. The experiment was found on a school website. I read the essay summarising the experiment and I thought the concept was pretty simple. It was basically filling out a rectangular straight-sided pan with water and to make sure the water bulged over the side of the pan. Then a wire rod was to be placed over the water near the middle of the pan. It had to just lightly touch the water. A single drop of oil was to be dropped into the middle of 1 section created by the rod. The oil was then to spread out over the surface of the water and when it had covered the whole surface between the side of the pan and the side of rod, the rod was to be moved another couple of inches to allow the oil to spread even more. It continued liked this until you were supposed to see the oil starting to break up and see fissures in what should look like a very thin blanket of oil over the water. As soon as this happened the rod must be left alone and the length and width of the oil blanket must be measured. The idea was that all the molecules started spreading out and just before the cracks could come, they would all be flatly the one beside the other, making the oil one molecule thick. A calculation was then given out to find out the height of these molecules. Volume=Length*Width*Height


Assuming the drop was 1 cubic millimetre and the oil's length was 400 mm and the width was 300 mm:






0.00000833mm is the supposed height of one oil molecule. If you want more details on this experiment, visit the site, but details were my exact problem.

When I tried this experiment I did everything the experiment told me to do. The thing is, it doesn't tell you a lot. A lot of variables that need to be known are not explained, for example, the type of oil, the amount of time the experiment takes, or even the water temperature. I used olive oil because it was the only oil I had. I wasn't able to reproduce this experiment even though I tried three times. The first time I used ambient temperature water and a tiny drop of oil from the tip of a needle. It didn't work. The second time I used ambient temperature water again but this time with a slightly larger drop which I think was roughly 1 cubic mm. I used a pipette for the drop this time. This time it seemed to actually spread but it spread out into a bigger drop VERY SLOWLY. I left it overnight and in the morning the drop had clung on the edge of my pan and it had broken down into several bubbles. The third time I used the same amount of oil but I used hot water. This time the drop didn't even bother spreading.

My conclusion is that I have no idea if the proposed answer they gave could be right or if it is downright wrong. If it is wrong then the experiment was probably found somewhere else and it was probably not carried out before putting it on their website. If it is right, then whoever wrote out the experiment did not do it properly because I could not carry it out due to missing details.

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