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# Osmosis Between Potato Tubes and Sugar Solutions.

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Introduction

Investigation - Osmosis Between Potato Tubes and Sugar Solutions Aim: We are aiming to investigate the effect of different sugar concentrations in distilled water on osmosis in small potato tubes. Trial Run: We did a trial run, and found that it would be much more efficient to put three potato tubes in each petri dish rather than just one, so we are using fewer petri dishes and less solution. We will then take the average weights of the three potato tubes before and after each experiment. It also means we will know that each potato tube in a certain petri dish is under identical conditions. We also found that when we made large amounts of solution much of it was wasted, as we only required very small amounts. Although we are dealing with small amounts of sugar that are difficult to weigh out, we will only make enough solution needed for the experiment to avoid wastage. By using electronic scales instead of manual scales we can accurately weigh the small amounts of sugar required. Background Knowledge: I know that when osmosis takes place, water moves through a semi-permeable membrane from a low concentration of a solution to a high concentration of a solution, and although the water molecules move both ways, there is a net movement from a region with lots of water molecules to a region with fewer water molecules. ...read more.

Middle

0.24 0.240 -0.007 -2.70 Using the last column, I plotted the results in a graph of percentage change against the concentrations and then used the computer to work out the line of best fit. I was then able to see where the line crossed the x-axis to give a percentage of sugar in the solution where there would be no change in mass, i.e. there would be no diffusion of water from or into the potato tubes. I worked out the Change by subtracting the Average Before from the Average After: e.g. 0.273 - 0.26 = 0.013 I worked out the percentage change by dividing the Change by the original (Average Before) and then multiplying by 100: e.g. 0.013/0.26*100 = 5.128% Conclusion: From my results, it is difficult to draw a firm conclusion, as there is a very large spread in the range of my results. The graph shows points plotted from the percentage change in mass at the different concentrations of sugar solutions, worked out from our results. There was no very obvious pattern or trend in my results. However, I have still found there is a gradual downward trend and there is a line of best fit on the graph that shows this, indicating that the mass change in the potato tubes was decreasing as the concentration of sugar solution was increasing. ...read more.

Conclusion

I would also use a syringe to measure the amount of solution we put in each dish so it was exactly the same each time. Next, I would make sure there were no little bits of skin left on the potato tubes that could affect the results. To further improve my results, I would leave more time to complete the experiment and leave all the potato tubes in the dishes for an hour to give more time for the osmosis to fully finish. I would also extend the range of concentrations of solutions beyond 13%, to 20% and hopefully we should find that the later results do show a mass loss, and it should hopefully create a more conclusive line of best fit. To extend the experiment, I would have to measure the mass change with a greater range solutions, such as 0.5%, 1.5% etc. This would give more results and hopefully would create a better line of best fit, so I would be able to draw a firmer conclusion. I could also extend the experiment by using the technique with different types of potato to see if they had different concentrations of sugar in them. A final way to extend the experiment would be to change the temperature of the sugar concentrations and to see if this had an effect on the rate of osmosis, as at higher temperatures the water molecules will have more thermal energy and will move faster. Phil Harford 11O ...read more.

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