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Experiment to establish the effects of varying water potentials on potato tissue.

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Introduction

Experiment to establish the effects of varying water potentials on potato tissue Aim: To investigate the effect of varying concentration of a certain sugar solution on the amount of osmotic activity between the solution and a piece of potato of a given size. Hypothesis: Osmosis is defined as 'the net movement of water or any other solution's molecules from a region in which they are highly concentrated to a region in which they are less concentrated.' This movement must take place across a partially permeable membrane such as a cell wall, which lets smaller molecules such as water through but does not allow bigger molecules to pass through. The molecules will continue to diffuse until the area in which the molecules are found reaches a state of equilibrium, meaning that the molecules are randomly distributed throughout an object, with no area having a higher or lower concentration than any other. For this particular investigation I think that the lower the concentration of the sugar solution in the boiling tube, the greater the mass of the potato will become. This is because the water molecules pass from a high concentration of water, (in the solution itself) ...read more.

Middle

2. Using a size 2 cork borer, I produced 5 cylindrical pieces of potato. 3. I cut the remaining pieces of skin on a white tile with a scalpel and, using a ruler and straight edge, I measured and cut the potatoes to 3.5cm in length. I then dried them lightly in paper towels and weighed them on the balance, noting their weights. 4. Using 2 measuring cylinders I measured out different amounts of sucrose solution and distilled water which I then poured into the boiling tubes to give 20ml of solution of different concentrations in each boiling tube. 5. I next placed the potatoes into the tubes and sealed them using the corks. 6. I then labelled each test tube with its concentration and the initial weight of the potato piece that it contained. 7. The following day, after 17 hours, I drained out the solutions and placed all the potato pieces on the paper towel in the order I had put them in the test tubes, to avoid confusion as to which potato came from which solution. 8. I dried each potato cylinder with the paper towel and then placed each one on the balance so that I could weigh them. ...read more.

Conclusion

This would ensure that I have an accurate amount of fluid in each test tube. A more accurate electronic balance could have been used, measuring to a greater number of decimal places (i.e. a smaller denomination than 0.1g). The lengths of the potato cylinders may not have been completely constant throughout, as it was only possible using my ruler to measure to a maximum of 1 decimal place. There was only one noticeably abnormal result (highlighted on the graph). This may have been caused by human error, such as failing to reset the balance after it was previously used. When drying the potatoes, both before and after putting them in the boiling tubes, I may have dried some pieces more thoroughly than others and so some would have had excess water, which would have added to the mass. I could maybe have used another method of drying them, such as a fan, but this could also have caused the potatoes to have 'shrivelled', reducing their mass. Ultimately, given the equipment available, I believe that I gained a complete and relatively accurate set of results, fulfilling my initial aims and whilst I have made the above suggestions for improvement, it is unlikely that they would have a significant effect on the overall outcome of my investigation. ...read more.

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