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An Investigation into the factors affecting osmosis.

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An Investigation into the factors affecting osmosis. Problem. In this investigation I am trying to find the effect of placing potatoes cut into French fries into salt solutions of different concentrations and the subsequent percentage difference in weight between potatoes placed in different salt concentrations. Hypothesis. Osmosis is the transfer of water from a region of high water concentration through a selectively-permeable membrane to a region of low water concentration. A selectively-permeable membrane will let through small molecules such as oxygen, water and glucose but will not allow larger molecules such as starch or protein. This can be seen in the diagram below: If a selectively-permeable membrane, such as a potatoes membrane, separates a solution of high water concentration(a hypotonic solution) from a solution of low water concentration(a hypertonic solution), the water will move in both directions at one time. However, more water will leave the solution of high water concentration than leaves the solution of low water concentration. When there is the same concentration gradient in both solutions, the system will be in equilibrium and no water will be exchanged although the water will continue to move around. ...read more.


For the 1.0M solution, put in 10cm� salt and no water. For the 0.8M solution, put in 8cm� salt and 2cm� water. For the 0.6M solution, add 6cm� salt and 4cm� water. For the 0.4M solution, add 4cm� salt and 6cm� water. For the 0.2M solution, add 2cm� salt and 8cm� water. Finally for the 0M solution, put in no salt and 10cm� water. * Label each test tube as to which molarity solution it contains. * Cut the potato slice up into long, thin French fries using the scalpel. * Weigh each French fry and record the weight. * Place a French fry into each solution. * Leave for 15 - 20 minutes, timing with a stopwatch or from a normal clock. * Take out all of the French fries and dry them. * Weigh each one and record the weight. * Repeat the experiment exactly. Results. Conclusion. My results show that in a solution of high salt concentration, the potato cells will decrease in weight and in a solution of low salt concentration the potato cells will increase in weight. I can see that the potato cells carried out osmosis. ...read more.


apple, parsnip or change the temperature of the solutions. I could also change my dependant variable so that instead of measuring the difference in weight of the potato, I could measure the difference in length or volume. If I were to change the temperature of the solutions, I would place potatoes weighed beforehand in solutions all of the same molarity and leave them for 30 minutes. When the 30 minutes has been I would take them out and weigh them then record the results. All the same variables would apply apart from the independent variable which would be changing the temperature rather than the molarity of the solutions. I predict that I would find in this experiment that osmosis would take place the most at a higher temperature. I think think this because at higher temperatures the solution's molecules would move faster and so reach the state of equilibrium faster. Overall, I feel that my results were quite accurate and fair and this is due to the precautions I took to make this a fair experiment. However, I believe there are still certain aspects that could have been made more reliable and had I had more time, I would have carried out these additional experiments and precautions. ...read more.

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