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Osmosis Investigation

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Introduction

Osmosis Investigation Aim I intend to calculate the effect of different concentrations of sugar solution on the volume of a potato. This will test the effect of different concentrations of solute on the process of osmosis. Prediction Osmosis is the flow of a solvent to an area of low solute concentration to an area of high solute concentration, or, equally, from an area of high solvent concentration to an area of low solvent concentration. Therefore, I predict that the higher the sugar concentration that the potato is in, the smaller it will shrink, and vice versa. Preparations Because I had deviated from the original plan, measuring the volume rather than the length of the potato, it was necessary to first perform a trial of my method. This involved dangling the potato cylinder into a beaker of water, without it touching the sides or bottom, and measuring the difference in mass between the beaker of water and the beaker of water with the potato in it. I performed this test, which verified that my method would work. To provide a fair spread of results, I chose to perform my experiment using the following concentrations of sugar solution: 1M, 0.75M, 0.5M, 0.25M, 0M (distilled water) ...read more.

Middle

This, however, depends greatly on whether out range is wide enough to encompass this possible curve. We cannot go much lower in concentration than 0, but what if the centre of the curve lies up around 0.75M - we would not have enough data to find the centre. We must therefore analyse the graph of the results. This is the kind of curve we must look for in the graph- evidence of osmosis happening more rapidly in the centre (near the original volume and concentration of the potato), and less rapidly at the ends, when little more water can move either way. It is worth noting at this point that visual evidence demonstrates that the centre point must lie within our range of results- some of them were clearly shrunken, whereas others were much larger than before. The visual evidence, however, was not enough to deduce the actual centre point. This graph shows the averages of all my results as displayed in the above table. Despite the possible presence of a slight curve at the far bottom of the graph line, the fact that this rises above the previous results makes it slightly dubious, and in any case we have no curve on the opposite end to find the centre from. ...read more.

Conclusion

As mentioned above, the major problem in my experiment was that with the initial measurement of the potato, and this seriously compromised the value of my results. I am still unsure about the cause of this problem; as far as I know I carried out the measurements correctly. I can only assume that I am wrong about this, or that the particular scales I used to measure the volume were faulty. The comments I make about how to improve the experiment will be imminently predictable; more time and more resources. A single hour is, frankly, insufficient time to prepare and implement an experiment such as this, especially combined with insufficient resources. Were I to have had more time, I would have made measurements on each and every potato cylinder before using them in the experiment, something that would have both protected against the problem I encountered, and given me more useful results, because I would have been able to identify varying amounts by which each specific potato had grown/shrunk. Aside from these improvements, if I were to repeat the experiment, I would do it with more potato cylinders using smaller intervals between the different concentrations, and I would have extended the range to look for evidence of the curve in the graph. Nicholas Clarke 11AH 1 Science Osmosis Investigation Clevedon Community School 03/05/2007 ...read more.

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