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Osmosis Investigation.

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Osmosis Investigation Introduction Osmosis is the passage of water from a region of high water concentration through a semi-permeable membrane to a region of low water concentration. The 'Semi-permeable membrane' is a very thin layer of material (cell membranes are semi-permeable) which allow some things to pass through them but prevent other things from passing through. The 'Cell membranes' allow small molecules like oxygen, water, carbon dioxide, ammonia, glucose etc. to pass through. BUT these will not allow large molecules such as starch, protein, etc. to pass through. The 'region of high concentration of water' is either a very dilute solution of something like distilled or pure water. In each case there is a lot of water: there is a high concentration of water. The 'region of low concentration of water' is a concentrated solution of something like sucrose. In this case there is much less water. Reason for Experiment In my experiment I will be discovering what happens to a plant cell (in my case a potato) when it has been put into a sugar solution. In my experiment I will be trying to find out what would happen if we place a piece of potato into a sugar solution of different quantities, mixed with water. So the input variable of my experiment will be how much sugar solution I am going to use in each test tube, and my outcome variable will be the mass of the potato when it has bee left in the sugar solution (after 24 hours). ...read more.


I will compare the results of my experiment with the results of someone else's to make my results more reliable OR I will repeat the experiment myself. Apparatus * 5 pieces of potato (each piece must measure to 5mm) * 5 test tubes * Sugar solution, different quantities (to see amounts please review 'solutions') * Test tube rack * 24 hr Stopwatch * Scales * Syringe * Results table * Cling-film The Solutions & Variables For my experiment I am using 5 different solutions with a large range of concentrations. Each test tube will hold a different solution and each of the solutions will be mixed with water. I will use a syringe to extract the amounts. The 1st tube will contain 4mm� of sugar solution and 16mm� of water (20% solution). The 2nd tube will contain 8mm� of sugar solution and 12mm� of water (40% solution). The 3rd tube will contain 12mm� of sugar solution and 8mm� of water (60% solution). The 4th tube will contain 16mm� of sugar solution and 4mm� of water (40% solution). The 5th tube will contain 20m� of sugar solution and no water (100% solution). There are several variables and we can control them. The temperature will be at room temperature and fairly cool. They will be kept in the same place with the same amount of sunlight, just in case this affects the process. ...read more.


I therefore have got the idea of osmosis mixed up and did not understand the outcomes of osmosis. But I did understand that the concentrations have travelled after taking part in the experiment. I did retake the experiment and I managed to get results which came very close to my last lot. But this time I understood what I was doing and what was happening and why it was happening. I have understood the process of osmosis more after actually doing the experiment and recorded what happened in the procedure. I think I could have made the test fairer by keeping the solutions the same temperature before AND during the experiment (and actually measuring the temperature to make sure of this) to see if this input variable affected the results, and by making sure the potato not only measured the same but weighed the same too. I should make these improvements if I am to do this experiment for a third time. I could extend it further by doing more sets of concentrations (in a bigger range) and to make the length of time (24 hours) into something a bit longer or shorter. I could also try an experiment involving osmosis in the form of animal cells and compare my results from this experiment, with ones from an animal cell experiment. I could see if there are any similarities between the two or if there are any big changes. Osmosis Experiment Biology Coursework Vikki Stabler 10J 02/05/2007 Page 1 of 4 ...read more.

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