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Find out if osmosis occurs in a potato, and how it affects the potato in different molar solutions of sucrose and water.

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Introduction

Sam Dixon 10E GCSE Biology Course Work Planning experimental procedures The Potato Investigation, Osmosis Aim: My main aim in this experiment is to find out if osmosis occurs in a potato, and how it affects the potato in different molar solutions of sucrose and water. Prediction: Osmosis is the movement from one side to the other of a semi-permeable membrane, when on one side of the membrane there is a solution of both large and small molecules, but on the other side there are fewer or no large molecules. So I predict that when the potato is submerged in dilute concentration of sucrose solution, the mass, as well as the length of the potato will increase. The semi-permeable membrane allows small water molecules to pass through it, but not the large sugar ones. There is a diffusion of small water molecules from side where there they are in high concentration to the side where they are in lower concentration. So I predict that when the potato is in dilute sucrose solution below 0.5 molar concentration, the small water molecules will be in higher concentration than the ones inside the potato, so they will diffuse through the semi-permeable membrane, to the side where there is a lower concentration, therefore, increasing the mass and length of the piece of potato. So, when in a higher concentration of sucrose solution, there will be a lower concentration of small water molecules outside the potato, so the water molecules in higher concentration inside the potato will diffuse out of the potato through the semi-permeable membrane, thus decreasing the mass and length of the piece of potato. ...read more.

Middle

This experiment proved that osmosis occurs through a semi-permeable membrane, in this case a visking tube. Over time, the mass of the boiling tube decreased, this was due to the diffusion of highly concentrated water molecules from outside the visking tubing, moving through its semi-permeable membrane, to the inside where there was a lower concentration of water molecules as the tubing contained sucrose solution. Safety: This is an important aspect in our experiment. So we should take this into consideration, no matter what. We will be using a very sharp knife, which could injure someone if it's not handled properly. And we should also be careful that the solutions don't get into our bodies internally, because we are not fully aware of the damage it could do to us. Obtaining evidence: After the experiment, I had to dry the potatoes first, so that the water outside the tissue of the potatoes wouldn't alter the weight of what it is supposed to be. I quickly took all of them out, and put them onto a piece of tissue paper, into their own groups. When obtaining my results, I reset the balance, so that it would read zero so as to obtain the most accurate of results. Analysis: On the graph shown above, I have made the 'different solutions' as my independent variable, since it won't be changing on any event. And I have made the 'percentage' as my dependent variable, because it doesn't change in any particular order or a pattern. ...read more.

Conclusion

The range of concentrations was adequate but I would possibly create more concentrations if I repeated the experiment so that I would have more varied results. 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. 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. There were not any out of the ordinary results, but some were not as close to the line as others. I may have caused this. When the potato chips were removed from the test tubes and dried I may well have dried some potatoes more thoroughly than others and so some would have more excess water, which would add to the mass. 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. However with all this said I think that the experiment was truly successful and I was very pleased with the complete comparison of my results with my initial prediction. ...read more.

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