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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.

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Introduction

Biology Coursework 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'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 an isotonic point, a state of equilibrium. This means that the molecules are randomly distributed throughout an object, with no area having a higher or lower concentration than any other; this will help me identify my aim because the isotonic point will be the most accurate place to see an average change in mass. For this particular investigation, I think that the lower the concentration of the sugar solution in the cup 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. ...read more.

Middle

I am going to measure the pieces in grams. I am going to use the same apple corer, so that all the cylinders are the same width. Key Factor: The factor that I am going to vary is the concentration of the solution, this is because it will give me a varied set of results, from which I can make a decent conclusion. Equipment: Scalpel Weigh Scales Five plastic cups Cylinder Sugar Solution Water Potato Apple Corer Tile Paper Towel Analysis: This graph shown separately gives the line of best fit for the percentage change in mass of the potato chips over the course of the experiment. My computer-drawn graph shows a very slight curve on that is leading to complete plasmolysis, whereby the potato cannot expand and take in any more water, but this is not evident enough to prove anything, and is more or less a straight line. There is a pattern on my graph, and this is, as the concentration of the solution increases, the percentage change in mass decreases. The graph shows that the percentage gain and loss is inversely proportional to the concentration. The gradient does change in my graph. The potato chip is becoming as flaccid as it possibly can, and so the change in mass of each cylinder concentration is becoming closer and closer together. ...read more.

Conclusion

As well as the potato, I could have found a more accurate way to measure out the solutions and to determine the sugar concentrations. 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 0.0g but to 0.000g. I could also have improved my results by looking at the experiment again, but in more detail around the isotonic point. There were not any out of the ordinary results, but some were not as close to the line as others were. This may have been caused by human error. Also, the bigger the potato cylinders, the more accurate the results are, as there is more surface and it will easier to notice the change in mass. When the potato chips were removed from the test tubes and dried, I may well have dried some potatoes more thoroughly than others may and therefore some would have extra mass, from the excess water. 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. Michael Boulter 10.7 ...read more.

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