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To investigate and find out the osmotic potential of a potato.

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BIOLOGY COURSEWORK: OSMOSIS AIM: To investigate and find out the osmotic potential of a potato. PREDICTION; I predict that the potato cores in the distilled water and weaker solutions, which contain low concentrations of salty water, will expand when left in the solution for a certain amount of time. I say this because the molecules in the weaker solution will diffuse to an area of higher solute concentration, the potato (which will be done by osmosis). I also predict that the potato cores in the 1.0 molar concentration of brine (highest concentration) will shrink this is because the molecules in the potato will diffuse in to the brine. This will also be done by osmosis, is the movement of water molecules from an area of weak solution to an area of strong solution through a semi-permeable membrane (cell membrane). Therefore the potato cores once left in the higher concentrated solutions will shrink. And the potato cores in the weaker solutions will expand. THEORY: Osmosis is defined as 'the movement of water molecules from an area of high water concentration to an area of low water concentration, across a semi-permeable membrane' (Collins, 1999). ...read more.


Therefore when osmosis does take place the mass and length of the potato cores will show if it has expanded or shrunk. SAFE TEST: To ensure that the experiment is safe I will have to do the following: * Be careful when handling glass objects such as the test tubes and other apparatus. * Be careful, not to spill solution * To make sure that all chairs are tucked in and coats and bags are hung up in the corner away from the experiment to avoid any accidents. * To make sure that all surfaces are clean and clear of any unwanted objects. * Make sure hands are washed before and after experiment. VARIABLES: The variable of this experiment is that different concentrations of salt water will be used. The concentrations being used are written below: * Distilled water (D/W) * 0.2 * 0.4 * 0.6 * 0.8 * 1.0(brine) There will be seven different concentrations to see what will happen to the mass of the potato in different concentrations of salt solution. APPARATUS * POTATO * POTATO CORER * 6 GLASS TEST TUBES * MEASURING CYLINDER * TEST TUBE RACK * DISTILLED WATER * BRINE * RULER * KNIFE * FILTER PAPER * MEASURING SCALES DIAGRAM: (please turn over and look at the next page) ...read more.


My results and graph show that my theory was right. My results do agree with my prediction. Which stated that the mass of the potato cores would decrease in the higher concentrations and increase in the lower concentrations. Therefore as my theory did state that osmosis is the movement of water molecules through a semi permeable membrane from an area of low concentration to an area of high concentration. EVALUATION: The experiment was easy to do. The results were right but not really accurate. The graph shows that something went wrong in the 0.4m concentrations. I think that the volume of liquid might have not been measured accurately. To improve my results I will have to follow my method more accurately. Take measurements of the volume of liquid more accurately. I could have repeated the experiment more than twice. I did do the experiment twice to get the average results. Over all I think the experiment went quite well. If I were to do the experiment again I would follow the method more accurately to obtain more accurate results. Also try to prevent any errors by keeping an eye on the experiment. 1 ...read more.

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