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Investigate the effect of varying concentration of sucrose in a solution on a potato cylinder of a given size.

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Introduction

An experiment to calculate the rate of osmosis in potatoes Skill Area P Planning Experimental Procedures Aim: To investigate the effect of varying concentration of sucrose in a solution on a potato cylinder of a given size Hypothesis: Osmosis is defined as the net movement of water molecules from a region of high water concentration, to a region of low water concentration, osmosis takes place across a partially permeable membrane, which only allows smaller molecules like water pass through it, and doesn't allow bigger molecules like sucrose to pass through. In this experiment the partially permeable membrane is the cell membrane of the potato cylinders. The water molecules will continue to diffuse until both sides of the partially permeable membrane have the same amount of water molecules and are equal- i.e. that there is the same amount of water molecules in the potato cylinder, than in the solution surrounding it. I predict that the lower the concentration of sucrose solution in the test tube the larger the mass of the potato cylinder will be. This is because the water molecules pass from a high concentration, i.e. in the water itself, to a low concentration, as there are more water molecules in the pure water solution than there is in the respective potato cylinder, due to osmosis the molecules will pass through into the potato, causing its mass to increase. ...read more.

Middle

- Stop watch Method: Prepare the 40mm potato cylinders with corer, ruler and scalpel, prepare the solutions (using syringe), blot (using tissue paper) the cylinders (roll for 5 seconds forward), weigh them, and record results. Using stopwatch, put respective cylinders in respective solutions (using china graph pencil to make sure we don't got confused, and time 25 minutes. After blot the cylinders, and weigh. Record results. Repeat method again for second set of results. Variables I am going to control To create a fair test certain aspects of the experiment will have to be kept the same whilst one key variable is changed. The key variable in this experiment is the concentration of the sucrose solution. If any of the non-variables below are not kept constant then it may influence my results, which would make this experiment an unfair test. For example if one of the potato cylinders was 50mm instead of 40mm, this could greatly influence my results, as then there is an extra 10mm of surface area for osmosis to occur. Below are the aspects I am going to control, as they could influence the experiment and make it an unfair test: - Temperature: by doing all tests in one room at a constant room temperature, as eat may cause a change in the kinetic energy of the molecules, thus speeding up the process of osmosis, and altering the amount of water molecules which may pass through the membrane, thus altering the mass of the potato cylinder. ...read more.

Conclusion

not to 0.00g but to 0.0000g. There were not any out of the ordinary results, but some were not as close to the line as others i.e. (2, -11.32), contamination or inaccuracies may have caused this. Also I felt that there must be another method of blotting, as I feel that I may have dried some more thoroughly than others, also next time I would have wiped the scales and my hands each time I came in contact with the cylinders, and perhaps this would have solved the anomalies on my graph. If the experiment was repeated, I could find another way to dry the potatoes that would ensure that all were dried in the same way for the same time. Also I had to use 3 different potatoes on different days, which may have affected the results as each potato has a different water concentration, perhaps I could conduct all the experiments using the same potato, or maybe be use a mention that measured water concentration- this would make my results far more accurate. However with all this said I think that the experiment was successful and I was pleased with the complete comparison of my results with my initial prediction. For further experiments I could measure how the varying concentrations of a sucrose solution affects the rate of osmosis on different vegetables; and see whether they reflect the results I obtained in this experiment. Anna Iqbal 10G 1/9 Biology Mrs Trustler ...read more.

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