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Investigate whether the different concentration of sugar solution will affect the weight and size of the potato cells.

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Planning Sector: Aim: To investigate whether the different concentration of sugar solution will affect the weight and size of the potato cells. General background information: Osmosis is defined as the movement of water or any other solution's molecules from an area in which they are highly concentrated to a region in which they are less concentrated. This movement must take place across a partially permeable membrane such as a cell wall, which lets smaller molecules (E.g. water) through but does not allow larger solute molecules to pass through. The molecules will continue to diffuse until the area in which the molecules are found to reach a state of equilibrium, meaning that the molecules are equally distributed throughout the cell, with no area having a higher or lower concentration than any other hence equal. Hypothesis/prediction: For this particular investigation I believe that the lower the concentration of the sugar solution in the test tube the mass of the potato will be greater and the longer the potato cells will be. This is because the water molecules pass from a low concentration to a high concentration, (in the potato chip). Therefore, the chips in low concentrations will gain mass and have a greater length height than in higher concentrations such as 1molar of sugar solution. If there is no gain or loss in height or mass then these will be the isotonic points of the potato cells. The isotonic point is where the cells are not increasing or decreasing in size and is known to be in a state of equilibrium. Apparatus: 1. Potato 2. Standard sugar solution (1molar) 3. Wash bottle 4. Test tubes and test - tube rack 5. Cork borer-size (4mm diameter) 6. Scalpel 7. Ruler 8. Wooden Board 9. Measuring Cylinder-size (250cm3) 10. Top-pan Balance 11. Paper Towels Variables: To enable fair test certain aspects of the experiment will have to be kept the same whilst one key variable is changed. ...read more.


I also measured the length of each chip using a ruler and this was also recorded in a table. > As I had time after doing the first set of results I redid the experiment under exactly the same conditions. This gave me many results, which gave me a more accurate view on the osmotic changes on the potato cells. Precautions which were taken: > I had to enable that all the non-variables remained the same in order to get the fairest possible results and therefore to get the best possible results for my investigation. > When I had to cut the potato into 8cm chips I had to be extremely careful as I was instructed that the scalpel was very sharp and could easily cause an injury if it was misused. > When I was placing the various concentrations of the solution into the test tube I had to be extremely precise in order that I didn't put too much or to less into the test tubes and the right quantity of water and sucrose were placed into the test tubes. > When handling the potatoes I had to be very careful and make sure my hands were clean and dry so that there was no contamination and I didn't pass on any excess water to the potatoes. Table of results: All results are shown are rounded off to 2.dp. The percentage change in length (or mass) is worked out by: Length (or mass) after - Length (or mass) before = X X / length before (or mass before) = Y Y x 100 = % percentage change 1st attempt: Concentration of sugar solution Length Before(cm) Length after(cm) % Change in length 0.000 molar 8.00 8.50 +6.25% 0.125 molar 8.00 8.20 +2.50% 0.250 molar 8.00 7.60 -5.00% 0.500 molar 8.00 7.30 -8.75% 1.000 molar 8.00 7.10 -11.25% Concentration of sugar solution Mass Before(g) ...read more.


An alternative solution would be to find a machine that would cut the chips for me and give me exact same weights and heights of each chip because the weights of my chips varied. If I was to repeat the investigation given more time I would try and find a machine that did this as it would enable me to have fairer tests and it would gain me time so I could record even more results. I also feel that the chips could have been measured to a more accurate scale perhaps using the weight in grams to four decimal places rather than two. I also found it quite arduous to measure out the molar concentrations to an exact amount. I feel an alternative to having placing the molar concentrations by a measuring cylinder would be using a burette, as this would enable me to obtain precise measurements. I was reasonably happy with the results that I obtained, as I believed that there were no major anomalies. I do believe though there were some close to becoming anomalies this could possibly been down to human fault. An example of a close anomalous result is the percentage change for 1.000 molar concentration length as in my results I got -10.5% but according to my line of best-fit -9.60% should have been the result I should have achieved. This could be because when the potato chips were removed from the test tubes and dried I may well have dried some potatoes more thoroughly than others may have been so the excess water may have contributed to the gain in length and mass. If I had more time to do the investigation I could have possibly found a resource that could have enabled the cells to be dried in the same way and the same time so this would contribute to a fairer test. On a whole I fell the investigation was successful and I was especially pleased with the positive outcome of my results with no major anomalies occurring. By Mohammud Malik ...read more.

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