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To determine the concentration inside potato cells.

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Introduction

Planning Aim: to determine the concentration inside potato cells. What is the molarity? Prediction: In a strong solution the cylinder of potato will float and in a weak solution the potato will gain weight. I predict that in a solution the same concentration as the potato, it will not gain or lose weight. This is due to osmosis, water molecules travel from an area of high concentration to a low concentration through a semi-permeable membrane until they reach equilibrium. This means that if the potato is in a solution with the same amount of water as itself it will not float or sink. (The living world- pg 14, Michael Roberts) Apparatus: * Cork borer * Beaker * Potatoes * Scalpel * Sucrose solutions * Goggles & apron Method: * The apparatus is set up as shown in the diagram. * Six sucrose solutions of increasing molarity will be taken between 0.0M (distilled water) and 1.0M to try and find the molarity of the potato cells. * Cylinders of potato will be extracted from a potato using a cork borer. * The cylinder of potato will then be cut into disks approximately 1.5cm long. ...read more.

Middle

Initial mass of potato (g) 2dp Final mass of potato (g) 2dp Difference in mass (g) 2dp Percentage change in mass (%) 0.0 3.39 3.60 0.21 6.19 0.2 2.81 2.87 0.06 2.14 0.4 2.45 2.44 -0.01 -0.41 0.6 2.51 2.48 -0.03 -1.20 0.8 3.28 3.17 -0.11 -3.35 1.0 2.96 2.56 -0.40 -13.50 X = anomalous results. Results no 3 Molarity of sucrose (M) Initial mass of potato (g) 2dp Final mass of potato (g) 2dp Difference in mass (g) 2dp Percentage change in mass (%) 0.0 2.21 2.29 0.08 3.62 0.2 2.64 2.69 0.05 1.89 0.4 1.78 1.74 -0.04 -2.25 0.6 1.79 1.70 -0.09 -5.03 0.8 1.46 1.33 -0.13 -8.90 1.0 1.91 1.71 -0.20 -10.47 I used my three sets of data to obtain an average. The three figures were added together and divided by three to give an average of all the three results. Any anomalous results were ignored when finding the percentage change in mass Molarity of sucrose (M) Average change in mass (%) 0.0 4.30 0.2 1.58 0.4 -0.63 0.6 -2.79 0.8 -4.80 1.0 -6.595 I decided to find the percentage mean because by using these figures I will be able to compare the water lost during each experiment relatively, taking into account the initial mass of the potato sample. ...read more.

Conclusion

If the glucose is taken with the potato it will make a difference as glucose is insoluble and therefore will affect the amount of water it can take up, if starch is taken then it will not affect the results because starch is insoluble. (Internet) When the potato was blotted each time there was no way to make sure that we blotted exactly the same amount of water off each time and this would make it unfair. If the samples were left for a long period of time then some of the water could evaporate and cause the results to be inaccurate. If the samples were taken from two or three different potatoes then there is no way of knowing if they contained the same amount of water as each other to begin with. Improvements: Samples should be taken away from any growths to ensure there is no excess glucose in the potato. The potato should be cut in more equal sizes because the surface area could affect the rate that osmosis works. Potato samples should be taken from the same potato so the results are known to be more accurate. My results match textbook ideas as they correspond with their findings. ...read more.

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