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Investigation To Find the concentration of sucrose solution that has the same "water potential" as potato tuber cells.

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Introduction

Aim: To Find the concentration of sucrose solution that has the same "water potential" as potato tuber cells. Hypothesis: Osmosis is defined as the net movement of water or any other solutions 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 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 test tube the larger the mass of the potato will be. This is because the water molecules pass from a high concentration, i.e. in the water itself, to a low concentration, i.e. in the potato chip. Therefore, the chips in higher water concentrations will have a larger mass than in higher sugar concentrations. Earlier on, we performed a preliminary experiment where we tested osmosis in potatoes. We used three things to test it. Water, sugar solution and air in beakers. In this experiment we found that after about 24 hours, all the chips seemed different to the other. The chips kept in water had become turgid, as in they swelled up, the ones in sugar solution had become flaccid, they become thin and smaller. With the ones in air there was no change. This happened because of osmosis and that the water molecules moved from one place to the other but did not even out, which explains the turgid and flaccid ones. ...read more.

Middle

8. I dried each chip with the paper towel and then placed each one, one by one, on the top pan balance to weigh them and their weights were recorded in a table. The time of removal for each set of potato chips was also recorded down. 9.With these results averaged, I will not need to repeat the experiment again. 10. Once the table is full with these results, I will average them out to get better readings and see if there were any anomalies within my results as I will have to analyse why and how this could have happened. 11. With the averages, I will plot a graph showing mass by morality. With this graph I will have an easier time analysing my results and evaluating it overall. With the graph, I hope to find a point where the mass remained exactly the same. Thus finding a point in between where the chip is neither flaccid or turgid, a point where the amount of water is exactly the same outside the chip and inside and where the mass has remained the same. Precautions: >The measurements for the solutions had to be perfect as to not change the out come of the experiment. >I had to ensure that every time I handled the potatoes my hands were clean and dry. This was to stop any kind of contamination and made sure that I did not pass on any extra water onto the potato. This small graph below shows how I hope the graph I plot with the percentage averages will turn out. As the molarity increases the percentage change become less until it reaches a point where there is no change in weight. ...read more.

Conclusion

There seems to be no logical explanation why is was so, and I would like to pursue it, to see whether they were not anomalies and were actually pure, correct results, this could disrupt my theory and prediction though but I wish to find out. The cutting of the potatoes was the most difficult part of the experiment as although I was recording my results by mass, it could well have affected the surface area and so the overall rate of osmosis. If I were to repeat the experiment I would have possibly found a machine to cut the potato as it would ensure that all potatoes would be the same weight and dimensions. As well as the potato I could have found a more accurate way to measure out the solutions and to determine the molar concentrations. Perhaps I could have used a burette. This would ensure that I have an accurate amount of fluid in each test tube. I could also weigh each chip on a more accurate scale, e.g. not to 0.00g but to 0.0000g. Drying the potatoes way also an important factor, each chips saturation would have affected the results, affecting how much water it could hold, what I would like to be able to do is completely saturate them so they are all of equal saturation and there is no great factor there. Drying them with tissue was also time consuming. Some of the anomalous results may have been caused by human intervention but that is why we repeated them, to reduce that factor. However with all this said I think that the experiment was quite successful and I was very pleased with the complete comparison of my results with my initial prediction, even with a slightly inaccurate graph. ...read more.

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