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Investigating how concentration of salt solution affects osmosis in potato

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"Investigating how concentration of salt solution affects osmosis in potato" By Neil Grant 1117 Planning We have been asked to investigate the effect of osmosis on potato chips. Osmosis is the diffusion of water from a lower concentration of solute to a higher concentration of solute, through a membrane. I have chosen to investigate the effect of the water potential/concentration of solution on potato chips. This means that I will put potato chips into salt solutions of different concentrations. These concentrations would be ones such as these; 0.25mola, 0.5m, 0.75m, 1.0m and distilled water. There are other factors (variables) involved and these are; � Temperature � Water potential of potato initially � SIZE of potato � Light intensity � Mass of potato dependent variable � Volume of solution potato chip is in � Type of potato � Time left in solution � Surface area of potato chip � Use the same balance to measure chip If I am going to conduct a fair test, then I am going to have to control these other factors. Doing all the tests at one temperature will control the temperature. For the purpose of my experiment I am going to do all the experiments at room temperature. To keep the water potential of the potato initially will be kept the same by using the same type of potato, which have been treated in the same way, e.g. have all been cut without being washed and peeled. ...read more.


(Osmosis is the movement of water molecules from a high area of water potential to an area of low water potential through a selectively permeable membrane.) If the cells are surrounded by a stronger solution, e.g. salt water, the cells may loose water by osmosis. To ensure safety, The potato chips will be cut on a white tile with a scalpel so that no one will be cut. Also while using scalpels everyone will have to wear safety goggles. My experiment is not experimenting the how permeable the membranes are, but it is testing the rate of osmosis with different solutions. We also know that diffusion of water will occur from a lower concentration of solute to a higher concentration of solute. I am saying that the higher the concentration that the potato chip is exposed to, the more water will move out of it making it lighter. Here are some diagrams to help explain. Obtaining Evidence My graph is a curve that slopes downwards and does not go through the origin. Because the line is not straight and does not pass through the origin, it means that the percentage gain/loss in mass and morality are not directly proportional. However, there is a pattern on my graph, and this is, as the morality of the salt solution increases, the percentage change in mass decreases. The gradient does change in my graph. it gets less steep as 'x' gets bigger. ...read more.


The graph is not a straight line through the origin which shows that the percentage gain/loss in mass and morality are not directly proportional either. The average distilled water gains in mass. This means that osmosis takes place and that the water moves from the beaker into the potato. The matches my initial predictions, and fits in with my prediction graph as well. The point where the line crosses the x-axis is the isotonic point. This is where no osmosis is taking place, i.e. no water is moving in or out of the potato. The next point, 0.25 molar looses approximately 4.0g. This shows that the water potential of the salt solution in the beaker is weaker than that of the potato chip. The next, 0.50 m, looses approximately 8.0g in mass. This shows that the salt solution has an even weaker water potential than 0.25 m and that osmosis took place. This is why the potato lost even more mass, and it shows that the water potential in the beaker is less than that of the potato chip. Also that the potato is trying to make the water potential of the fluid on both sides of the semi permeable membrane the same, (osmosis from the potato to the salt solution, from a higher water potential to a lower one). This pattern carries on through the graph, and even more mass is loss, as more water moves out of the potato. My results tally with my initial predictions. These were that osmosis would take place, and as the water potential decreases, morality increases, the percentage change in mass will decrease. Evaluation ...read more.

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