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Osmosis in Potatoes.

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GCSE Science Coursework: Osmosis in Potatoes Planning Introduction: Osmosis is the special name used to describe the diffusion of water across a membrane, from a dilute solution to a more concentrated solution. In biology, this usually means the diffusion of water in and out of cells. Osmosis is just one special kind of diffusion because it is only water molecules we are considering. Molecules will diffuse from where there is a lot of them to a region where they are fewer in number; that is, front a region of highly concentrated molecules to a region of lower concentration (below). In a plant cell, when water molecules enter it, the vacuole will fill and push against the cell wall. The cell will become very firm, or turgid. If a plant is in an environment where there is not much water, water will leave the plant cells and move into the cells with less water. The vacuole will shrink and the plant will wilt. When even more water leaves the cell, the cell membrane tears away from the cell wall. This is called plasmolysis. To prove this, I will be performing an experiment in which I will place potato cylinders into various sugar/water solutions for 24 and observing the effect this has on the potatoes. ...read more.


This is because more or less solution may be absorbed depending on time. I am going to keep each potato chip in each solution for 24 hours, in a boiling tube. The surface area of the potato chips will be kept the same by having all the chips the same size. This must be kept the same because the amount of surface area exposed to the solution may effect the rate of osmosis. The thickness of the chip will already be the same, so I will cut the length so that each chip is 5cm long. To make the mass readings more fair, I will take each chip of the solution, roll all the surfaces gently on a paper towel, to remove all excess solution, and I must not squeeze the chip. I am also going to use the same balance to weigh my potato chips. This is because the measurements may slightly vary between scales. To ensure safety , the boiling tubes will be kept in beakers so that they can not be knocked over. Prediction I predict that the higher the concentration of sugar solution the more water will move out of the potato chip. I also predict that the more sucrose the solution contains, the softer the chip will be, due to loss of water from a cell. ...read more.


The most dramatic difference was between 0.25 and 0.5 percent, when the graph dipped suddenly. Overall, the graph corresponds to my prediction that the higher the amount of sugar in the solution, the higher the loss in mass. It also proves that this happens rapidly. Although I didn't predict that. Evaluating Evidence My results were, on the whole, accurate. Apart from one anomalous result at 1.0 molarity, which was disregarded. I believe this happened because I dried the chips too vigorously when I took them out of the solution, which would have a great bearing on the results. I believe the method we used to investigate Osmosis was the best possible and I can't really think of a better one right now. We tried to carry out the experiment as fairly as possible. However, we ran out of potato a few times and had to keep using different potatoes, which may have affected our results slightly. I think that if ten solutions were used instead of five (0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0 ) were used, we would have got a much more accurate overlook, especially when it came to the transition between 0.25 and 0.5 molarity. I believe that even with the anomalous result, the measurements were good enough to support my prediction. Maybe to get a view of how Osmosis works in different situations, a different plant could be used. ...read more.

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