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Osmosis Coursework

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Osmosis Coursework Aim: My aim is to find out what effect different concentrations of salt solution has on a potato chip when left for a certain amount of time. Also my main objective is to find the isotonic point of a potato. The isotonic point is the point at which the concentrations of water are the same at each side of the semi-permeable membrane (in each region). When there is equal flow in each direction through the membrane, when the water is diffusing into the cell and out of it at the same rate. Plan The variables that could affect osmosis in my investigation: * Potato Chip Area/Mass/surface area * Amount of water * The Molar of the solutions * The temperature of the solutions * Amount of time the chips are in the solutions I am going to find out the isotonic point of a potato by varying the Molar of each solution, so my input variable is the Molar of the solution and my outcome variable is the percentage change in mass of each potato chip after they have been submerged in a solution of a specific Molar for an amount of time. I am going to keep these variables the same to keep my investigation fair. * Same potato used for potato chips * The temperature of each solution (degrees Celsius) ...read more.


I am going to time the chips in their solutions from the minute my helpers and me place the chips in the designated solutions and then I am going to leave them for 15 minutes. I am going to have helpers because I want to make sure my results are as reliable as possible by keeping the chips in their solutions for exactly the same amount of time. I think 15 minutes is a sufficient amount of time for osmosis to noticeably take affect. When the time is up I am going to get my helpers to help me take all of the chips out of their solutions at the same time and put them on a paper towel to take off the extra solution that is on the chips, then I am going to measure the new masses of the chips and record them in the relevant tables. Results of main experiment I kept the temperature of the solutions at 17 degrees. I made sure there was exactly 50 ml of solution in each beaker. The mass varies between each chip because I am recording percentage change in mass. The chips are 50mm in diameter. I used this equation to work out the percentage change in mass: 0.2M Original mass (grams) Mass after 15 mins (grams) % change in mass (grams) ...read more.


inside the cells are getting closer to osmotic pressure so the water flow into the cell starts to slow down that is why the graph is less steep at the beginning of the curve and it is less steep at the end of the curve because it is getting closer to having no pressure in the cells so when there is no pressure in the cells no water can flow out the percentage in mass change will stay the same or start to reverse. I could have improved my investigation by using four chips in each experiment instead of two because this would make my results twice as reliable as I would get a better average change in mass and there fore a better average percentage change in mass, and my results may of produced less anomalies. Also if I had the time in lessons I would have left them in their solutions for 20 minutes, as this would also make my results more reliable because I think 20 minutes gives osmosis I better time to occur and this may have prevented some of my anomalies in my results and make my results more reliable and accurate. If I was to use twice as many solutions (0.1M, 0.2M, 0.3M, 0.4M,--,1M) I would have twice as many points on my graph which would give me a lot more accurate isotonic point and therefore make my investigation more accurate. Will McClintock Page 1 ...read more.

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