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To find the osmotic pressure of potato cells.

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Osmosis Aim To find the osmotic pressure of potato cells. I can find this out, when there is no net movement (change of mass in potato cylinder) when placed in different concentrations of sugar solution. Background Information Arrangement and movement of particles in solids, liquids and gases. Solids have strong forces of attraction between molecules. The molecules are held in fixed positions, in a very regular lattice arrangement. They keep a definite shape and volume. Solids can't be compressed because the molecules are very close together. Solids are generally very dense. Liquids have some force of attraction between molecules. The molecules are free to move. Liquids don't keep a definite shape. The molecules are constantly moving in random motion. Liquids can't be compressed because the molecules are already packed closely together; liquids are quite dense. Gases do not have a force of attraction between their molecules. The molecules are free to move. Gases don't keep a definite shape or volume. The molecules are constantly moving at random. Gases can be compressed and have very low densities. Diffusion This is the movement of a substance from a region where it is at a high concentration to a region of lower concentration. i.e. down a concentration gradient. Particles that make up a gas or a liquid always move around. If there is a lot of one type in one place and few of them in another, then particles move to where there are fewer. Eventually the particles will be spread about evenly. They move from where there is a high concentration to where there is a low concentration. This is diffusion. Osmosis Osmosis is a special type diffusion, it is the movement of water molecules from a region of high water concentration (a dilute solution) to a region of low water concentration (concentrated solution) through a semi-permeable membrane. A semi-permeable membrane is a very thin sheet of material. ...read more.


surface area of potato cylinder. * Concentration of the sugar solution Output variables * Change in the weight of potato pieces The importance of keeping the variable the same is vital, because it might effect our results. Also I'm going to explain whys its important to keep this variables and explain how this would effect my set of results. * Temperature = the temperature must be kept constant, because If I increases the temperature, it enabling the water particles to move faster, which makes the osmosis process faster, which will effect the overall result. * The volume of the solution should be kept the, because the higher the volume, the more water, which makes the solution dilute on the other hand the less volume, the less volume which makes the potato's to have more solution * If the length if times are not kept the same, then the water molecules will have more or less, time then the other experiment, therefore increases the volume of the potatoes. * If the weights are not the same the same then this would mean that the number of particles in the potatoes are not equal and therefore the concentrations inside the potatoes might not be the same. This would lead to different amount of osmosis taking place, as the starting concentrations need to be the same inside the potatoes to allow the solution concentrations to be varied * If the potato pieces are not the same exact shape this will mean that the surface area of the pieces is not equal and this would lead to a different of osmosis taking place with more occurring where the surface area is larger. The starch molecules in potato are bigger and can't go through the semi permeable membrane and to the pure water solution. But the water molecules are much smaller and can go through and swell the potato. ...read more.


As well as the potato I could have found a more accurate way to measure out the solutions and to determine the molar concentrations There were not any out of the ordinary results, but some were not as close to the line as others. 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. If we were to this experiment again we would have larger pieces of potatoes to get a more precise measurement by using s ruler or we would need a microscopic measurements (a length smaller than a mm) to get an accurate size so that all the length are the same. we would do proper repeats rather than putting three in one boiling tube and counting it as a three repeat. I would also get a weight measurer that is more effective (as in measures very light weigh). After comparing my graphs to a couple of graph's graphs, I found out that we had the corrected and very reliable graph drawn, with a lines of best fit. This ensures me that my sets of results were very much corrected. On my graph I have drawn a straight line form my correct set of results. I have also seen others 's group's graphs and I have figured that I have drawn the correct line on the graph. I believe we gained accurate and sufficient enough results, shown on our graph and tables that concludes the experiment, and to prove our hypothesis. My final results were very reliable, due to the precautions I took to make this a fair test. ...read more.

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