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Investigate the effects of varying sugar concentration on the amount of osmotic activity between the solution and the potato tubes cut to a given size.

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Introduction

Aim: To investigate the effects of varying sugar concentration on the amount of osmotic activity between the solution and the potato tubes cut to a given size. Hypothesis: Osmosis is defined as the net movement of water molecules from a region in which they are highly concentrated to a region in which they are less concentrated. This movement takes place across a partially permeable membrane e.g. a cell wall. This means that the cell wall will let 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, in our case (when both the potato cell and the solution have the same amount of sugar solution concentration,) Method: To make it a fair test certain aspects of the experiment had to been kept the same while only one variable was changed. The variable was the concentration of the sugar solution. This gives us a very varied set of results from which we could make a conclusion. If any of the non-variables below were not kept constant it would mean it would not be a fair experiment. For instance if one of the potato tubes was 1cm longer than all the other potato tubes this would therefore mean more space for osmosis to occur. ...read more.

Middle

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. I also repeated the experiment once again; this gave me the most accurate results I could have hoped for. !!!!!!!!!!!!!"����"$$$$$$$$$$$$$$%%%%%%%%%%%%^&^&&&&&&&&&&&&*( Conclusion: When the concentration reaches , there appears to be no further water loss or gain, suggesting that the cell is fully plasmolysed. From the graph an estimate to the concentration of the potato cell can be made as 0.28M, as this is the point where the potato is not increasing or decreasing in mass, this is known as the isotonic point. This is where no osmosis is taking place; both the potato and the solution have an identical concentration. The time I used to test the potato chips was plenty of time to allow sufficient osmosis to occur as. However if I was to repeat this investigation I might decrease the time of the experiment because I don't think it would have taken 1 week, as I believe osmosis would occur within a couple of hours. ...read more.

Conclusion

I could have also found a more accurate way to measure out 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. 0.000g not 0.00g. The range of concentrations was adequate but I would possibly create more concentrations if I repeated the experiment so that I would have more varied results, i.e. 0.1M, 0.2M, 0.3M, 0.4, 0.5, 0.6 etc. 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. I think I took just enough results but if I were to do this investigation again I would certainly take more so that I would have a greater chance of obtaining more reliable ones. There were no out of the ordinary results, but some were not as close to the lines as others. This may have been caused by human mistake. When the potato chips were removed from the flat dishes and dried I may well have dried some more thoroughly than others and so some would have more excess water, which would add mass. If the experiment was repeated I could find another way to dry the potatoes, which would ensure that all were dried in the same way for the same amount of time. ...read more.

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