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An investigation into osmosis using a pealed potato and different concentrations of salt solution.

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Introduction

Sheena Shah 11AL Osmosis in a Potato Chip Aim: An investigation into osmosis using a pealed potato and different concentrations of salt solution. Hypothesis: I predict that in this experiment, a higher concentration of salt solution will move to an area of low concentration of a solution. The definition of osmosis that the CGP Science Book gives is "Osmosis is the movement of water molecules across a partially permeable membrane from a region of high water concentration to a region of low water concentration." This means that if the potato is surrounded by a solution, which has a low concentration, the mass of the potato will decrease, as the high concentration from the potato will move onto the water, there for increasing the volume of water surrounding the potato. The partially permeable membrane in this experiment is the surfaces of the pealed potato. It will let the salt solution pass in and out of it, therefore increases or decreasing the mass of the potato. The GCSE Science Class book says, "Osmosis is a special type of diffusion. It occurs across a permeable membrane, which allows some particles to diffuse through it and not others. Most cell membranes are like that, being permeable to water and some solutes only." This means that the potato will definitely allow water to go in and out and should also allow the salt solution to enter it. I predict that the higher the concentration of the salt solution, the more solution will move out of the potato chip. Osmosis is the flow of a solvent of a solution, through a membrane. The membrane blocks off the other components so that they cannot flow through. ...read more.

Middle

* The type of solution that I use. A sugar solution would give different results to a salt solution. Therefore as I am using potatoes with salt solution in them, I will be using a salt solution too. Equipment: > A large potato > A measuring cylinder > A ruler > Weighing scales > 5 beakers > A potato borer > Salt solution- 0.5m, 1.0m, 1.5m, 2.0m, 2.5m > Stop clock > Knife > White cutting tile > Paper towels This is a diagram of the experiment I am carrying out. Safety: To keep myself safe during this experiment, I will make sure that the area I am working in is clean and safe, that there are not bags on the tables or on the floor which could cause an accident. When using the knife to cut potatoes, I will keep my fingers away from the blade. After I have used the solutions, I will wash my hands so that any excess solution will be washed away. Plan: * Collect equipment and place in a safe and clear working area. * Measure 75cm� of each solution using the measuring cylinder (0.5m, 1.0m, 1.5m, 2.0m, 2.5m) and pour into the beakers. * Use the potato borer to cut out 15 potato chips. Cut them to 4cm each using a knife, ruler and white tile. * Weigh each potato chip with the same weighing scales. Record the results. * Place three potato chips in each of the five solutions at the same time and record the time. By placing three chips in each of the five solutions, I can carry out three experiments at the same time, which will save time. ...read more.

Conclusion

This result may have been anomalous because of the room temperature. The temperature in the room could have varied and therefore affecting the result. Another reason for this anomaly could be because of human error. A mistake when measuring the potato could have occurred. The result could have been a mechanical error too, as when the potatoes were weighed; extra weight could have accidentally got onto the scales. The other results obtained were fairly accurate as I weighed the potatoes correct to 2 decimal places. If I were to carry out his experiment again, the main changes I would make would be to use a varied range of salt concentrations. For example 0.25m, 0.50m, 0.75m, 1.00m, 1.25m etc. This would give me accurate results and I would be able to find the isotonic point more accurately too. I would also use better equipment, such as a computerised weighing scale, which would give more accurate results. Instead of results 0.0g I would have results 0.000g. I would also try to find a machine that would cut the potatoes into exactly the same size chips. This would save time and make the experiment very accurate. I found that cutting the potatoes was the most time consuming. Another change I would make is to experiment with potatoes of a different type. These would have a different concentration to the potatoes used in this experiment and therefore would give me different results which I would be able to compare with the results from this experiment. Another variable I could investigate into would be the amount of solution used. Instead of using 75cm�, I would use more, such as 100cm�. This would tell me whether the amount of concentration used in the experiment varied the results or not. However, I am pleased with the set of results that I obtained and feel that this experiment has gone well. ...read more.

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