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GCSE Biology - Osmosis Coursework

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GCSE Biology - Osmosis Coursework Potato and Osmosis Investigation Skill Area P: Planning Aim: To investigate the effect of varying concentration of a certain sugar solution on the amount of osmotic activity between the solution and a potato chip of a given size. Hypothesis: Osmosis is defined as the net movement of water or any other solution´┐Ż|s molecules from a region in which they are highly concentrated to a region in which they are less concentrated. This movement must take place across a partially permeable membrane such as a cell wall, which lets smaller molecules such as water through but does not allow bigger molecules to pass through. The molecules will continue to diffuse until the area in which the molecules are found reaches a state of equilibrium, meaning that the molecules are randomly distributed throughout an object, with no area having a higher or lower concentration than any other. For this particular investigation I think that the lower the concentration of the sugar solution in the test tube the larger the mass of the potato will be. This is because the water molecules pass from a high concentration, i.e. In the water itself, to a low concentration, i.e. In the potato chip. Therefore, the chips in higher water concentrations will have a larger mass than in higher sugar concentrations. The graph above shows a simple curve obtained when the concentration of the solution is plotted against the percentage change in mass. "Y At point A the graph tells the viewer that no osmosis has occurred, suggesting that the concentration of water inside the cell is equal to the solution outside. "Y At point B (high water concentration), there is no indication that the cell is increasing further in size. ...read more.


5. Using a measuring cylinder I measured out different amounts of sucrose solution and distilled water which I then poured into the test tubes in a percentage ratio giving me the various molar concentrations. 6. I then weighed every potato chip on an electronic balance and recorded the weights. 7. I swiftly put 3 potato chips into each beaker and then started my stopwatch. 3 chips were used to create an average which gave me a better set of results and more accurate graphs. 8. Whilst waiting I set out some paper towels with which I was going to dry the paper and I drew up a basic table for my results. 9. After 30 minutes I drained out the solutions in the sink and placed all the chips on the paper towel in the order I had put them in the test tubes as to not confuse myself as to which chip came from which solution. 10. I dried each chip with the paper towel and then placed each one on the scales so that I could weigh them. 11. Each potato was measured accurately on the electronic scales and then the weights were recorded. 12. As I had time after doing the first set of results I redid the experiment under exactly the same conditions. This gave me secondary set of results which gave me a more accurate view on the changes. Precautions: "h As was stated in my planning section of the coursework, I had to keep all of the different non-variables the same, to make sure that none of them affected the results of the experiment in any way. ...read more.


0.10m, 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 as although I was recording my results by mass, it could well have affected the surface area and so the overall rate of osmosis. If I were to repeat the experiment I would have possibly found a machine to cut the potato as it would ensure that all potatoes would be the same weight and dimensions. As well as the potato I could have found a more accurate way to measure out the solutions and to determine the molar concentrations. Perhaps I could have used a burette. This would ensure that I have an accurate amount of fluid in each test tube. I could also weigh each chip on a more accurate scale, e.g. not to 0.00g but to 0.0000g. There were not any out of the ordinary results, but some were not as close to the line as others. This may have been caused by human. When the potato chips were removed from the test tubes and dried I may well have dried some potatoes more thoroughly than others and so some would have more excess water, which would add to the mass. If the experiment was repeated I could find another way to dry the potatoes that would ensure that all were dried in the same way for the same time. However with all this said I think that the experiment was truly successful and I was very pleased with the complete comparison of my results with my initial prediction. ...read more.

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