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Investigation On Osmosis

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Introduction

Investigation On Osmosis By Alex Rignall Investigation On Osmosis Aim To investigate how much change there is in the mass of a potato chip in varied concentrations of a sucrose solution. Prediction Osmosis: Osmosis is the movement of any of the solutions 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 cell membrane or a partially permeable membrane, which lets small molecules through and does not let large ones through. I predict that the lower the concentration of sucrose in the solution the more the potato chips will expand. I can say this because I know that there will be more water molecules and therefore osmosis will take place between a lower concentration of water molecules and a higher concentration of water molecules that are separated by a partially permeable membrane such as a the cell membrane of the potato. The sucrose will not cross the partially permeable membrane because the molecules are too big to fit in between the gaps in the membrane. The higher the concentration of sucrose in the solution the more the chips will decrease in mass. I can predict this because from my previous prediction I know that the potato chip will have a higher concentration of water molecules, and therefore the water molecules in the potato chips will move across the partially permeable membrane (the cell membrane) ...read more.

Middle

We could not use the same potato for all the chips because it was not big enough and we also could not ensure that the next potato was similar. We could however make sure the potatoes cam from the same place and this would therefore help make the experiment fair. We tried to control the temperature as best we could but there is no way we can make it exact and constant in such a large room, so the rate of the osmosis may have been affected by temperature. We did try and minimize all the above by leaving the petri dishes out for over 24 hours. Results I collected results from the first experiment and recorded them in the table below. I then worked out the percentage change of the potato chips. (Percentage change = Difference between before and after/Original) Solution Weight before Weight after % Change experiment (g) experiment (g) 0 molar 3.34 4.105 23 .25 molar 3.43 3.52 2.60 .50 molar 3.37 2.825 -15 .75 molar 3.31 2.39 -28 1 molar 3.43 2.21 -36 When I repeated the experiment in recorded the results in a graph like the one above and again worked out the percentage change. Solution Weight before Weight after % Change experiment (g) experiment (g) 0 molar 3.11 1.975 14.4 .25 molar 3.26 3.24 -0.6 .50 molar 3.24 2.64 -18.5 .75 molar 3.11 1.975 -36.5 1 molar 3.36 2.32 -31.0 In order to make it a fair ...read more.

Conclusion

The other variable that was hard to control was the amount of solution in each petri dish. We wanted 50ml in each one but by using a measuring cylinder some may have been left inside a not gone into the petri dish. To make it more accurate next time I would use a burette. There where no results that where completely off the line but there is one that I would like to discuss. I tried to rule out abnormal results by taking an average of them all but it seems that I should have repeated the experiment more to rule out this abnormal result. It is the result for .75 molar that is the odd one out, it measured at a 32.25% loss but the best fit line shows it should have been about a 29% loss. This result on the best fit line would have been closer to the first result telling me that my two chips taken for 0.75 molar where from a bad part of the potato. This result rules out the possibility that the first experiment chips where dried too much with the paper towel because if it was then the best fit result would have been closer to my second experiment result. I admit that some of the chips may have been dried too much but not as much to change the result by 7%. However even with this result I am satisfied that my experiment was very successful and that my results are accurate enough to have been analyzed. ...read more.

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