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Investigate the factors affecting the rate of Osmosis.

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Planning Osmosis is the diffusion of water from a lower concentration of solute to a higher concentration of solute, through a partially permeable membrane. In a high concentration of water the amount of solute (e.g. sucrose) is low. This could be called a weak or dilute solution. In a low concentration of water the amount of solute is high. This could be called a strong or concentrated solution. When a partially permeable membrane divides two such solutions, the water will move from the area of high concentration to the area of low concentration until both sides are equal. In plant cells water flows through the cell wall and cell surface membrane into the vacuole from the outside. As a result, the cell swells up. It doesn't burst as the cell wall stops the cell expanding too much; at this point we say a cell is fully turgid. Aim The purpose of my investigation is to investigate the factors affecting the rate of Osmosis. The key factors I have found affect this are: Length - of membrane Temperature - of water Concentration - of solution The factor I am going to investigate is the concentration of the solution in which the potatoes are placed. By doing this I will have to control all other factors to ensure a fair test, these are; doing all the tests at room temperature to control the temperature as a higher temperature would mean diffusion would occur quicker. ...read more.


2 for each test tube as it will be more accurate than 1 and give a more accurate result, as I will be able to then work out an average. * Find the mass of the potato pieces in grams correct to 2.d.p using electronic balance. If necessary cut a small piece off potato to make all pieces of an even mass. * Measure solutions into test tubes as follows; 1. 20cm distilled water, 0cm sucrose solution 2. 18cm distilled water, 2cm sucrose solution 3. 16cm distilled water, 4cm sucrose solution 4. 14cm distilled water, 6cm sucrose solution 5. 12cm distilled water, 8cm sucrose solution 6. 10cm distilled water 10cm sucrose solution Put solutions into test tubes and place in test tube rack. * Place 1 pin with 2 pieces of potato into the test tubes and place bung in. * Leave at room temperature out of direct sunlight for 24 hours. * After 24 hours I will take my results by re-measuring each potato mass and recording it. Results and Analysis The table below shows my raw data. The last column was worked using the formula; Mass after-mass before = change in mass Solution Mass before (g) Mass after (g) Change in mass (g) Reading 1 Reading 2 Reading 1 Reading 2 Reading1 Reading 2 0 moles 1.09 1.14 1.77 2.02 0.68 0.88 0.1moles 1.1 1.12 1.71 ...read more.


I also found my first set of readings unhelpful but as I had done 2 sets of readings I could take an average of the two to make my results more reliable. This did mean my overall percentage increase might have been slightly different, as these results would have affected them. If I did this experiment again I would be more careful in my setting up the experiment to ensure my results would be accurate. I had problems cutting the potatoes so they may have ended up slightly different sizes, which would account for any anomalous results. Another reason the results could have occurred may have been because the potato cores were not completely submersed in the sucrose solution. The final weighing may have not been accurate as not all the cores were blotted dry properly before weighing. Sugar solution sticking to the core would have increased the final mass artificially. To eliminate this bias I could have invented a universal blotting regime or measured length increase instead of mass. For a further experiment I could have investigated the effect other factors had on the rate of osmosis. The temperature of the water in the sugar solution is one. It would prove that the protein in the potato membrane denatures after the optimum temperature (usually about 35 degrees c.) and osmosis would no longer occur as the membrane is destroyed. Another factor that may have been investigated could be the increase in length of potato chip. ...read more.

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