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Investigate the effect of varying concentration of a certain sugar solution on the amount of osmotic activity between the solution and a potato chip of a given size.

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Introduction

Biology coursework My aim is to investigate the effect of varying concentration of a certain sugar solution on the amount of osmotic activity between the solution and a potato chip of a given size. The osmosis theory Osmosis is defined as the net movement of water or any other solution 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. The effect of this process is to eventually dilute the solutions. Osmosis occurs due to the kinetic theory of matter, the theory of the movement of water molecules in gases. As water molecules are always moving in different directions and through partially permeable membranes, when there is a weak solution and a strong solution and a semi permeable membrane which allows osmosis to occur. There is more water molecules in the weak solution and these water molecules will eventually move into the stronger solution through the partially permeable membrane until both sides of solution are of equal strength. Different membranes allow different parts of the solution around to pass through them. Some allows all of it to go through while some only allows parts of it to go through. Out of these only a few allows selective flow which is needed for osmosis. Plant cells always have a strong cell wall surrounding them. When they take up water by osmosis they start to swell, but the cell wall prevents them from bursting. Plant cells become turgid when they are put in dilute solutions. ...read more.

Middle

I have decided that I am going to use six concentrations of solutions each with a difference of two concentrations. The practical is going to be repeated two times. The first time, the concentrations used will range of readings that have a reasonable gap, enough to plot graphs and see if my prediction was correct. From the results that this experiment will provide me with, I can make an accurate conclusion, I can also find out the points where the osmosis reaches the isotonic point. I can then find the particular range of readings in my results where the concentration is the same inside and outside. I will develop my experiment into a deeper investigation using closer range of readings to find the exact point where the concentration is the same on both sides. I am going to use a range of reading with a difference of 0.2molars concentration for my experiment. The reading that will be used are; 0m, 0.2m. 0.4m, 0.6m, 0.8m, 1.0m. A digital weight will be used to make sure my readings are accurate. I think that if I used smaller unit I would be more accurate with my results so I am going to be using small units e.g. mm, ml, molars etc for my results. I am going to make sure that I do all my experiment in a constant temperature. This is the variable that I have to control and the variable that I have to change is the concentration of solutions. Practical Apparatus Distilled water- 25ml Sucrose solutions of 0m, 0.2m.0.4m,0.6m,0.8m,1.0m - 25ml of each concentration Boiling tubes-6 Digital weighing machine-1 Knife-1 Potato-1 Cork borer-1 Stop watch-1 Method planning A range of sucrose sugar solutions will be prepared with concentrations of molars varying from 0m, 0.2m,0.4m,0.6m,0.8m,1.0m. This will be done by adding varying amounts of distilled water to varying amounts of sucrose solution. Sections of potato will be cut using a cork borer and will be measured and weighed. ...read more.

Conclusion

The time that I used for the experiment to last was enough to allow sufficient osmosis to occur. However if I was to repeat the experiment I will increase the time span of the experiment, to allow more osmosis to happen and possibly find out the saturation point of the chips. 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, i.e. 0.10m, 1.15m, 1.20m, and so on. This way would have allowed me to also find out the isotonic point. 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. Extend the experiment To extend the experiment, we can do a detailed one to find out the correct concentration of water in which the internal and external pressure around the cell will be the same, so there will be an equal amount of flow into the cell as there is to the outside of the cell. We could do a detailed experiment on this idea by doing the same experiment that I had done before and then after I have plotted the graph, I should see where about the mass of the potato chip doesn't decrease. I could then make solutions that are more accurately diluted according to these guides and do my experiment to find out the correct point where osmosis is the same. 1 Biology Coursework Mariya Abdulla Candidate no: 4001 ...read more.

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