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The effect of varying concentrations of a sugar solution on the amount of osmotic activity between the solution and a potato chip of a certain size.

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Introduction

Osmosis Coursework Aim: To investigate the effect of varying concentrations of a sugar solution on the amount of osmotic activity between the solution and a potato chip of a certain size. Plan: For my experiment, I will need the following equipment: - 5 clean test tubes. - A test tube rack. - Sugar solution of the following 5 concentrations: 0M, 0.5M, 1M, 1.5M and 2M. - Scales. - A ruler. - A borer. - A knife. - Potato(es). - Paper towel. - Sticky labels. This diagram shows how I will set up my equipment for the experiment: [Equipment diagram here] I will be measuring the length (in centimeters) and the mass (in grams) of the potato chips before and after my experiment. To create a fair test, certain aspects of my experiment will have to be kept the same whilst one key variable is changed. I will be varying the concentration of the sugar solution. The 5 different concentrations I will be using are: 0M, 0.5M, 1M, 1.5M, 2M. This will give me a varied set of results from which I hope to make a decent conclusion. If any of the non-variables below are not kept constant it would mean it would not be a fair, accurate and reliable experiment. ...read more.

Middle

Knowing that osmosis will occur across a semi-permeable membrane whenever there is a difference between the water concentrations on the two sides of the membrane, and knowing that when this happens to cells they will either become turgid if water flows into them, or plasmolysed if water flows out of them, I want to test this theory: If the concentration of a solution in which the potato chip is placed is greater than a certain level the chip will contract, and if the concentration is less than that level it will expand. This can be seen in living cells. The cell membrane in cells is semi-permeable and the vacuole contains a sugar/salt solution. So when a cell is placed in distilled water (high water concentration) water will move across the semi-permeable membrane into the cell (lower water concentration) by osmosis, making the cell swollen and hard. The cell is now referred to as "turgid". The pressure inside the cell rises and eventually the internal pressure of the cell is so high that no more water can enter the cell. This liquid or hydrostatic pressure works against osmosis. When this is done with the potato cells, the cells will increase in length, volume and mass because of the extra water. ...read more.

Conclusion

I think I took easily enough results for the amount of concentrations that I was using, and the time that I used for the experiment to last was enough to allow sufficient osmosis to occur. However, if I was to repeat the experiment I might try to find out the saturation point of the chips. The range of concentrations was adequate but I would possibly create more concentrations of I repeated the experiment so that I would have more varied results, i.e. 1.10M, 1.15M, 1.20M, and so on. This way would have allowed me to also find out the isotonic point far more accurately as the one that I estimated is very approximate. The cutting of the potatoes was the most difficult part of the experiment because although I was recording my results by mass, it could well have affected the surface area and so the overall rate of osmosis. I could also weigh each chip on a more accurate scale, e.g. not to 0.00g but to 0.000g. There were not any anomalous results, but some were not as close to the line as others. This may have been caused by human error. When the potato chips were removed from the test tubes I may have dried some potatoes more thoroughly than others on the paper towel and so some would have more excess water, which would add to the mass. ...read more.

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