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To find out the concentration of salt inside potato cells by conducting an experiment that uses the principles of osmosis.

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Introduction

Aim: To find out the concentration of salt inside potato cells by conducting an experiment that uses the principles of osmosis. Background Information: Osmosis is the movement of water molecules from a high concentration to a low concentration until equilibrium is reached. This only involves the movement of water and is therefore different to diffusion. A situation where osmosis is extensively used is in plants, where they use it to get water from the roots to the rest of the plant. This also ensures the efficiency of the plants hydrostatic skeleton. The principle for this type of transport, being only water based, is the use of a selectively permeable membrane. The membrane consists of phospholipids. These have to main components, a hydrophilic head and a hydrophobic tail. These molecules then arrange themselves into a bilayer. This bilayer has a hydrophobic interior, which forms the basic anatomy of the membrane. Water particles are small enough to fit through this bilayer, and so can freely pass through it. However, such particles as sugar or salt are too big to fir through the membrane and are thus kept out. Prediction: I predict that if the salt solution is hypertonic, higher than the inside of the potato, the potato should lose weight. ...read more.

Middle

* Leave experiment for 48 hours, to allow the process to complete. * Empty test tube of water through a sieve and then collect the left over pieces of potato, remove and excess water with a paper towel. * Weigh the new potato and make a record of the readings. * The experiment if now complete, except for the analysis of results, each experiment should be finished with the cleaning away of equipment and any other mess created. * Log all results into a table, and make comparison between the starting weight and finishing weight, then take an average weight for each concentration. Fair Test: here are the key factors that I incorporated into my experiment to make it a fair test: * All potato used was from the same potato ensuring the same salt concentration throughout. * Using scales, very accurate measurements are taken to make sure that we can get an accurate result at the end of the experiment. * The scales where further used to ensure the accurate measurement of salt concentration. * The experiment was repeated so that an average could be taken, giving a more accurate result. ...read more.

Conclusion

Also our skin sweats, and sweat contains salt, this could have affected the experiment both when taking results and when primarily setting up the experiment, cutting the potato. To counteract this I could have used some equipment that would not affect it in this way. Conclusion: From my graph I can conclude that the internal salt concentration in a piece of potato is approximately 3.2 grams per litre. I think though that the test for 4 grams per litre was anomlaous, and therefore voids this conclusion. If this result was maybe -3.5%, then the result would be 3.5 gramms per litre. However the reasons for this not being an anomalous result, are the other results taken at concentration above it, they are all fairly close together suggesting that this is right. Overall from my experiment, we can see how osmosis works, trying to obtain an equilibrium. This helps scientist a great deal, especially when tryin to find the concentration of salt in water, or something similar. My experiment has been beneficial as it has shown me how hard it is to be accurate and fair when doing an experiment, and has given me experience. In conclusion I think that my experiment was a success, and showed clearly the effects of osmosis. ...read more.

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