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Investigating Osmosis

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Introduction

Biology GCSE Science 1 Assessment Investigating Osmosis Planning Experimental Procedures The aim of this investigation is to find what factors would affect the size of a potato cylinder, when it is left in sucrose solution. I have chosen to investigate how concentration affects the size of a potato cylinder when placed in a sucrose solution Prediction I predict that the lower the concentration of the sucrose solution, the larger the potato cylinders will be. The higher the concentration of the sucrose solution the smaller the potato cylinders will be, this is because of osmosis. Osmosis is a special case of diffusion, where water moves from a high concentration to a low concentration, across a semi-permeable membrane. When the concentration of the sucrose solution is high, water inside the potato cylinder diffuses across the potato cell membrane, to the sucrose solution, this is to balance the solution out, when this happens the cylinder shrinks because it has lost water. If the concentration of the sucrose solution is low, the water in the sucrose solution will diffuse across the potato cell membrane, into the potato, when this happens the potato will grow because it has taken on water. ...read more.

Middle

The Apparatus 12x 50mm potato cylinders 200cm 1molar sucrose solution 15cm ruler 6 x test tube 50cm measuring cylinder Chinograph pencil Test tube rack 200cm distilled water Filter paper 6 x beaker The Method I will use the 1molar sucrose solution and the distilled water to make up each of the six sugar solutions according to the volumes given in the table. I will then label each beaker so I know the concentration of each solution. Next I will remove the potato cylinders from the beaker they are in. I will measure the chips to make sure they are all approximately 50mm; I will then record the lengths in my table. When I have done this I will place two potato cylinders in each test tube and carefully pour the solutions I have made, into each test tube until it covers the two potato cylinders, I will then use the chinograph pencil to write the details of the solutions I used on the test tubes. I will leave each cylinder in its solution for 15 minutes and then remove them. ...read more.

Conclusion

There was one anomalous result, which is probably because I made a mistake while measuring the concentrations. In conclusion as you increase the concentration, the size of the cylinders decreases and as you decrease the concentration, the size of the cylinders increases. Evaluating Evidence I think there is sufficient evidence for my conclusion; because I repeated the experiment three times, this does add accuracy to my results, as any anomalous results should be removed when I took the mean. To avoid any impurities I used distilled water. The results may not be entirely accurate, as one of the points does not lie on the line of best fit on my graph. I had one anomalous result, which could be the result of when I was measuring the concentrations for each solution; I may have made mistakes because I could not measure exactly the right amount of sucrose and water. To improve the accuracy of my results, I could have left the cylinders in the solution for longer. For further work I could investigate the control variables (Temperature of the solution, Skin on the potato, volume of the solution) and I could have used a wider range of concentrations. ...read more.

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