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Osmosis
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By Kimberley Snaith Had graphics, may need editing. Contains results table but got scrambled, may need redoing or decoding!! Osmosis is the movement of water molecules from a high water concentration to a low water concentration, passing through a partially-permeable membrane. A partially-permeable membrane (or semi-permeable) has very tiny holes which allows only certain substances to pass through. This means that water molecules can pass through at a steady flow. The glucose-rich region will collect a high amount of water, acting as if to even up the concentration. Osmosis makes plant cells swell up and become turgid. I am going to investigate the rate of expansion of a piece of potato using different concentrations of sugar solution. I am going to use six different solutions ~ thus being my input variable. Each solution will have three pieces of potato soaking in it, so I will have a more accurate result at the end. The six concentrations I will be using are: * Purely water * 0.2 molar of sugar solution * 0.4 molar of sugar solution * 0.6 molar of sugar solution * 0.8 molar of sugar solution * 1 molar of sugar solution To ensure that my investigation will be a fair test, there are some aspects I need to take into consideration. These are called ‘variables’ and are factors that are within my control, which could affect the results of my experiment. I need to make sure all the beakers are the same size, and that equal amounts of solution are in each beaker. If there is more in one beaker than the other, that could mean more water molecules will pass into (or out of) the potato, therefore the results would not be accurate. The potato pieces should all start off the same size. If one piece was 1cm and another was about 5cm, that would mean that there would be room for more water/sugar molecules, and could affect the rate that it would grow or shrink. The potato pieces also need to be soaking in the solution for the same amount of time. If one was soaking longer than the others, it would mean that there was more time for osmosis to happen; therefore the size may have changed more than it would have in the same timescale as the other pieces of potato.
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