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What osmosis is?

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OSMOSIS COURSEWORK What osmosis is? Osmosis is the net movement of a solvent through a semi permeable membrane (as of a living cell) into a solution of higher solute concentration that tends to equalize the concentrations of solute on the two sides of the membrane This means that... If you were to put cell into liquid containing water one of three things will happen. * If the medium surrounding the cell has a higher water concentration than the cell (a very dilute solution) the cell will gain water by osmosis. Water molecules are free to pass across the cell membrane in both directions, but more water will come into the cell than will leave. The net (overall) result is that water enters the cell. The cell is likely to swell up. * If the medium is exactly the same water concentration as the cell there will be no net movement of water across the cell membrane. Water crosses the cell membrane in both directions, but the amount going in is the same as the amount going out, so there is no overall movement of water. The cell will stay the same size. * If the medium has a lower concentration of water than the cell (a very concentrated solution) the cell will lose water by osmosis. ...read more.


How Will The Variable Be Controlled What Is The Effect Of Changing The Variable On Your Results Length Outcome I shall use a ruler to measure 2 cm lengths of potatoes. Having a longer potato chip may make more net diffusion happen and therefore make the results different for the different solutions. Thickness/surface area Constant I will keep the thickness the same by using the same borer throughout my experiment. A larger surface area will mean the net movement will be larger and will result in a larger potato chip at the end. Temperature Constant I will put the solutions in the same dark place on the three nights so that the temperature will be approx the same. A thermometer will be placed in the dark cupboard to check this. A higher temperature will lead to a faster movement of all of the molecules involved in this experiment. This inevitably will lead to a faster rate of osmosis for higher temperature as the water molecules will move faster across the membrane. Concentration of the solution Input I will change the concentration of the solution by 0.1M for each boiling tube. This range will be 0M - 0.4M giving me 5 values to test in a good range. The concentration of glucose solution should allow osmosis to occur at different rates. ...read more.


However, in doing this we could have removed water that was not excess, and altered our results. Another inaccuracy was when we put the potato chips into the solutions, because it was impossible to not leave a small interval between each test tube. The first test would have been going for a few seconds longer than the last. In future I should have asked people to help me to drop the chips into the test tube at the same time. The second point that I have plotted (at 0.1 molar) seems to be an anomalous result. It does not fit with the natural curvature of the graph. This suggests something went wrong. The reason for this is inaccuracy may be that I used the mean when plotting my graphs. That way, the information is clear and can be understood quickly, however, the disadvantage of this, is the fact that if one of the three results is inaccurate, the mean will also be. I believe that this is the reason for the anomalous results. I could extend this experiment by investigating osmosis with a different factor as opposed to concentration of water. I could investigate the effects of temperature on osmosis, or weight. This would give me a very clear understanding and knowledge of osmosis in potatoes. ?? ?? ?? ?? Page I GCSE Biology ...read more.

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