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Osmosis in potatoes

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Osmosis in potatoes Aim My main aim in this experiment is to find the isotonic level of water in a potato cell cytoplasm. We have to work out the salt concentration in the cytoplasm in terms of molarity. To find this I will test pieces of potato in different molar concentrations. From 1 molar solution to pure water. If there is no change in weight then I have found the isotonic solution, explain Apparatus � Knife - to cut the potato � 50cm3 and 25 cm3 Measuring cylinder - to measure the solutions � Water - part of the experiment Potatoes - part of the experiment � Tissue paper - to dry the potatoes after the osmosis takes place � Scales - to weigh the potatoes � Apple borer - to cut out potato cylinders Variables The variables are the things that make a test fair. The test must be fair because if it isn't then it could affect the results. * The Independent Variable is the variable that you can change. The thing that I will be changing in this experiment will be the salt solution concentration. This will help me to investigate the result of the affect that the amount of salt concentration in the solution that affects potato cell cytoplasm. * The Dependent Variable is the thing that changes because of the independent variable. This is the change in the weight of the potato, placed in different solutions of salt. The weight will be measured in grams by using scales. I will not be measuring the length because, it is very difficult to measure small pieces of potato using a ruler, which is an inaccurate device for something this small. ...read more.


Method I believe this task is in theory simple, but measuring out the solutions and getting the weights of the samples equal could be quite difficult. If the solutions are measured poorly then it could drastically affect our results. There will be an amount of control in this experiment. The potatoes do not have to be exactly the same but must be similar. One set of experiments will be carried out on the same day and all the experiments will remain in the same room I the same place. Problems may occur as water could evaporate, also the room temperature could change on different days. There will not be a strict amount of control on the potato weight because of there is a 0.1g difference between them then it will not affect the weight change dramatically. First, I will prepare the potato by peeling it. I will then push the apple borer through the potato, cutting into it lengthways. Then I will cut the cylinder into three equal lengths, which will all be altered until they, are all very similar. I have to do this twice so I have 1 cylinder for each solution. I will be doing 3 experiments so I need to do this 6 times. 1 cylinder of potato will be placed in one beaker of each molar solution. The solutions are left for 24 hours. The potatoes were placed in a 0.0 molar solution, a 0.2 molar solution, a 0.4 molar solution, a 0.6 molar solution, 0.8 molar solution and a 1.0 molar solution. Each molar solution will be set up first and will then be ready for the potatoes to be placed into them. ...read more.


My final results were fairly reliable, due to the precautions we took to make this a fair test, but I'm a bit disappointed that the second experiment brought out 4 anomalous results. I believe that this could have occurred, because of poor measuring and also that the weather affected our results, because the temperature may have been significantly different, and affected water evaporation, making the water more concentrated. To improve this experiment, I believe that we could have done all the experiments at the same time, so that the weather could not affect each experiment differently. We could also have used 1 litre of water, and a larger sample of potato. If the water samples were larger then it would help accuracy as an extra 2cm3 would not have affected the experiment very much. It would also have been easier to weigh the potato if the sample was larger, because the potato mass would have made it easier to measure the weight difference. We could also have used the same potatoes because different potatoes may have different isotonic salt concentrations. This could also have caused the anomalous results in experiment 2. The scales we used were also inaccurate and only measured to 1 decimal place, this made it harder to find exactly, how much weight had been lost or gained. If we had more time to do the experiment we could have done the experiment many more times and found a much better and accurate average. Also we were unable to record our experiments exactly 24 hours later due to lesson times. If we worked in a laboratory, with carefully controlled conditions and better equipment, then I think we could have done this experiment a lot more accurately, and a lot quicker. ...read more.

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