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Osmosis in Potato Chips

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Introduction

Year 11 GCSE Biology Coursework - Osmosis in Potato Chips Aim This experiment is to find out how osmosis in potato chips is affected by the concentration of sucrose solution present in the solution around it and also the ways in which osmosis occurs i.e. where the water molecules involved are travelling. Prediction I think that the higher the concentration of sucrose in the solution around the potato chip, the more weight the chip will lose as the experiment is run. I also think that in a concentration of sucrose where there is a lot more water than there is sucrose that the chip will gain weight as the experiment goes on. I think this because in a solution where there is a low water concentration, where a potato chip with a higher water concentration is placed, osmosis dictates that water will pass out of the potato chip (down the concentration gradient), out through the cell's semi-permeable membrane and into the solution. This is how osmosis works. Osmosis is: The movement of water molecules from a high concentration of water, through a semi-permeable membrane into a low concentration of water. In this case, there would have to be a higher concentration of sucrose in the solution to give the solution a low water concentration. This would mean that the potato chip would have a higher concentration of water. The movement of water molecules from the chip into the solution would culminate in the mass of the potato chip decreasing as the test goes on. In the other case, where a low concentration of sucrose is added to the solution, the water concentration would be much greater in the solution than in the potato chip, so the effects would be reversed and water molecules from the solution would start moving in through the potato chip cells semi-permeable membranes. This movement of the water molecules from the solution and into the potato chip would result in an increase in the chips weight as the test runs on. ...read more.

Middle

Again there are safety issues here. Make sure you do not force the stopper into the test tube as you may break it. Try and find a stopper that fits easily into the test tube. 4. After every two hours, take the chips out and measure their weights. Make sure to dry them with blotting paper before weighing as this could affect the results, making the potato chips appear to be heavier than they are. The water on the outside of the chip doesn't count because the chip has not absorbed it. 5. After 24 hours the experiment will be finished. Take the final measurements and then dispose of all equipment safely and correctly. All test tubes, syringes, razor blades, tiles, mounted needles and boiling tubes must be put into a box for cleaning. 6. Record all results accurately and work out an average for each concentration (average weight of chip after testing). I will need to make sure that my results are precise so I end up with a correct and fair experiment. Extra care must be taken when weighing the chips so that mistakes are not made in the recording. I will then be able to see if my prediction is justified by the final results. The preliminary results suggest that my prediction was right because they show that when there is more sucrose present in the solution, the chip will weigh less because it has a lower water potential than the solution. My preliminary test wasn't as accurate as it could have been as it was not very thorough and I only tested one test tube of each solution. This means that I will have to wait for my main results to be able to see if it is correct or not. Results Concentration of Sucrose, % Mass of chip, g Mass of chip after 2 hours, g 4 hours, g 6 hours, g 24 hours, g 0 8.27 8.48 8.88 9.10 9.72 0 7.93 8.13 8.41 8.59 9.13 0 7.92 ...read more.

Conclusion

If I were looking for additional evidence to support my prediction I would want to take concentrations of 0.1 mol, 0.3 mol, 0.7 mol and 0.9 mol as well as those I have already done to make sure that my trend line was right and still supported my prediction. I think I would have also liked to continue the experiment by weighing each potato chip every two hours instead of just during school hours and I would have liked to leave the experiment for 48 hours to see when osmosis reaches a point where it has to stop. I believe that osmosis is limited because it works in trying to balance the concentrations of water present in both the solution and the potato chip and so I think that there must be a point perhaps during 48 hours that it has to stop and cannot go any further. I have already explained my theory on turgid cells and that there must be a point where the cells have too high a pressure that any more water can enter them and that this is when water potential becomes obsolete because the water concentrations have become the same. I also think that when a cell loses water there must be a point where the water concentrations are balanced between the potato chip and the solution and so it does not have to give up any more water molecules. However I would like to have found out at what point osmosis stops and how long it takes to balance out the water concentrations in solutions with different concentrations of sucrose. Also I would have liked to find out if any other factors affect osmosis and how they affect them. By changing my controlled variables to something like heat of water or surface area of potato chip I would be able to find out more about the factors that limit osmosis and in which way they limit it. ?? ?? ?? ?? ...read more.

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Here's what a teacher thought of this essay

5 star(s)

*****
A detailed account with clear results tables and explanations. Some minor errors.

Marked by teacher Adam Roberts 20/05/2013

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