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effect of changing the concentration of a solution on the movement of water into and out of potato cells

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Introduction

Introduction I have been asked to investigate the effect of changing the concentration of a solution on the movement of water into and out of potato cells. I will be able to change the input of my experiment. The input variable will be the concentration of the solution. The 100% solution is sodium chloride dissolved in water (salt water). This will be referred to as the 100% solution from now on. But the type of solution is not important as Osmosis is all about differences in concentrations. The output variable will be the weight of the potato chips, the movement of the water into and out of the potato. Osmosis is the diffusion of water through a semi-permeable membrane from high concentration of water to a low concentration of water. The water molecules move freely through the semi-permeable membrane this is a passive process. We will do this experiment by placing potato chips in different strength solutions and checking for mass increase/decrease. Prediction I hypothesize that if we place potato chips in different strength solutions that there should be different results, some with noticeable changes in mass the other will be nearly the same. The potatoes should gain/lose mass by the movement of water. If there is a change in mass it is because water has entered or left the cell. So the experiment will be based upon the movement of water. The first potato chip will be placed in a zero percent solution. ...read more.

Middle

This will allow us to see whether osmosis has taken place, and to what extent. The volume of the solution that the potato chips are kept in must be fair. The must be totally covered in the solution, and the amount of solution will be kept the same because all the potato chips are the same size. I am also going to use the same scales to weigh my potato chips. This is because the measurements may slightly vary between scales. Preliminary Work We decided to do some preliminary work so that we could see what results to expect in the final experiment. Also we could then get information from them and use that information to compare with our final results these would tell us if we have any anomalous results. In the preliminary work we followed the plan exactly. On the next page is a graph showing the results. Solution (%) Starting weight (g) End Weight (g) Change in weight (g) Percentage gain/loss 100% 0.47 0.28 -0.19 -59.57% 50% 0.36 0.37 +0.01 +2.70% 0% 0.39 0.56 +0.17 +69.64% These results confirmed my hypothesis but theses are only one set so they could be anomalous results. Therefore I had to do more experiments on a larger scale with more variables. The preliminary work did help. It showed me that we had to dry the potato chips before you weighed them. Also when you are inserting the potato chips into the boiling tubes you make sure that you have labeled them correctly, I found out the hard way. ...read more.

Conclusion

Therefore the larger the surface area the more water that can be diffused. So if a potato chip has a large surface area but has the same weight as another potato chip then the potato chip with the larger surface area will take on more water in a set time. For example if a potato chip is cut in a wavy shape or is crinkled it could have the same weight as any other potato chip but it would have a larger surface area. This could affect your results. So you must be careful in cutting the same shape potato chips. The slight difference in our experiment was negligible so we did not take it into account but it might have helped to make one of those anomalous results. All the anomalous results were negligible. They could be caused by anything. Form a slight increase in room temperature to the cell membrane being damaged when being cut. If I were to repeat this experiment I would try to make sure there are no anomalous results. The experiment would take a longer time and would be conducted in a sterile lab where there are no possible ways of the experiment being effected. In conclusion the experiment was a success we got the results we expected and they proved our hypothesis. But this experiment could always be repeated maybe on a much larger scale over and over again. This experiment suggests that there is a connection between the concentration of a solution and the movement of water. Daniel Jones 10B - 1 - ...read more.

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