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Test how the molarity of a water/sucrose solution affects osmosis in potatoes.

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Biology Coursework - Osmosis Aim The aim of this experiment is to test how the molarity of a water/sucrose solution affects osmosis in potatoes. Prediction I predict that as we lower the molarity of the solution (a solution with a higher concentration of water) the potato's mass will increase more than with a high molarity solution (a solution with a higher concentration of sugar). I have based this prediction on the research I have done on osmosis, using "The Hutchinson Softback Encyclopedia." Osmosis is the term given for the process of water passing through a semi-permeable membrane from the higher concentration solution to a lower concentration. Constants The things that will stay the same are: * The total volume of solution * At the start of the experiment each potato cube will be 1cm? * The ambient temperature and the temperature of the solution * The length of time the potato cube is in the solution Variables The things that will change are: * The molarity of each solution and this will change by increasing the amount of sucrose as the amount of water ...read more.


Before I weighed a cube I had to remove excess surface moisture using the paper towel. I then measured out the 5 different Molar solutions using the measuring cylinder. The amount of water/sucrose in each solution is shown in this table. Molarity Volume of Water (ml) Volume of Sucrose (ml) 1 0 100 0.75 25 75 0.50 50 50 0.25 75 25 0 100 0 I placed 3 potato cubes on each paperclip, the paperclip was used to space the cubes apart so that the solution could reach each surface of the cube, giving the same surface area. I placed each paperclip in a different Molar solution. I then left each solution for 2 hours, I timed this using a standard analogue clock. I used 3 potato cubes in each solution to make it easier to identify any anomalous results. I then used the average reading from each test tube for my results table. I removed each paperclip from the solution and removed each potato cube from the paperclip. ...read more.


I gained these results from another classmate in my Biology class. Table to show the increase in Mass of the Piper potato cube Molar Mass Before (g) Mass After (g) Difference (g) Increase/Decrease 1 0.61 0.67 0.06 I 0.75 0.61 0.71 0.10 I 0.50 0.61 0.76 0.15 I 0.25 0.61 0.87 0.26 I 0 0.61 1.04 0.43 I This shows that a similar amount of increase in mass occurs as the Molarity of the solution decreases. Conclusion Valor potatoes increase in mass according to the molarity of a water/sucrose solution when left for 2 hours. This is because the concentration of water inside the potato is much lower than the concentration of water in the solution. Osmosis occurs because the cell walls of potatoes are a semi-permeable membrane so the water from the solution passes through into the low concentration in the potoato. Evaluation I tried hard to keep the constants the same for each test tube. This was quite difficult using a scalpel. To improve this I could have used an apple corer or similar to cut a piece of potato. ?? ?? ?? ?? Matthew Smith 11BHu Mr Bullamore 1 ...read more.

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