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An investigation to show the effect of concentration of sucrose solutions on osmosis in potato cells (length and mass)

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Introduction

An investigation to show the effect of concentration of sucrose solutions on osmosis in potato cells (length and mass) Planning Prediction: I think that when a potato is placed in a pure water solution, it will increase in mass and size because I predict that osmosis will occur. Osmosis is the movement of water from a region of high concentration to a region of low concentration through a partially permeable membrane. Osmosis will occur because the potato cells contain a solution of sugar and when they are placed in a solution of pure water, the water particles will move from the high concentration to the low concentration through a partially permeable membrane, which in this case the cell membrane. Plan: I will carry out an experiment in class to prove my prediction. For the experiment, I have chosen a potato because the cell sap concentration in the cells is high. I will place potato chips in different concentrations of sucrose solutions and measure their lengths and weights before and after to compare them for my results. I will leave the chips for approximately one hour in the solutions. I will record their mass in kilograms to 2 decimal places and length in centimetres to 2 decimal places also. I will have six different concentrations of solutions and place three chips in each. ...read more.

Middle

0.5 0.55g 0.41g -25% 2.37cm 2.25cm -5% 1.0 0.60g 0.42g -30% 2.52cm 2.25cm -11% After drawing a graph, the results show that the ratio of water moving in and out of the cell membrane is equal at 0.22M. The preliminary experiment went well and the results were as I expected them to be. This has helped me with my plan because now I have an idea of what range of concentrations I want to use and when I carry out my experiment, I will know how to set everything up. This will help me a lot because it will save time and it should be easier for me. Obtaining (See results table on the next page) Analysis I have found out that when the potato chips are placed in a strong sucrose solution, they lose water through osmosis, therefore the mass and length decreases. When the chips are placed in pure water, they gain water through osmosis, so their length and mass increases. For instance, when the chips were placed in a 1.0 molar solution, the mass of the potato chips before was 1.37g and after was 0.96. It is clear that they lost weight. When they were placed in pure water, their average mass before was 1.33g and after was 1.45, therefore they have gained weight. ...read more.

Conclusion

This is for 2.0 and 1.0 molar. I think that this is probably due to human error. This proves that the results for mass are more reliable than length, probably because the mass was measured by electronic scales, so they are more reliable. In my opinion, the procedure I used was quite suitable although if I wanted very accurate results I could have produced more repeats or increased the range of concentrations of solutions. I wouldn't say that my results are very reliable because of the three anomalous results, but overall they do fit the pattern, therefore they are reliable to some extent. From drawing the graph, I can see that the mass results are more reliable than those of the length. This is because I had to measure the length using Vernier Calipers which are quite difficult to read off. I think the anomalies are therefore down to human error. My results are still sufficient for me to form a conclusion. It was easier for me to obtain the results of the mass, which is why I would concentrate mainly on mass if I had to repeat the experiment. I could carry out further work to extend this investigation. For instance, I could place potato chips in a solution which has the concentration of the isotonic point. If the mass and length do not increase or decrease then it would prove that my results are extremely accurate. ...read more.

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