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GCSE OSMOSIS PRACTICAL COURSEWORK

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Introduction

OSMOSIS PRACTICAL COURSEWORK Investigation of the concentration and the effect of sucrose on Osmosis in apple and potato tissues INTRODUCTION: - I will be doing an investigation on the topic of Osmosis (A special type of diffusion). The aim of this experiment is to investigate the effect of sucrose concentration on osmosis in apple and potato tissues, to find out how the concentration of sucrose solution affects the mass of potato and apple strips. So therefore to find out about the uptake of water into a cell which depends on two main factors, which are: - > The water concentration of the solution > The water concentration of the cell sap in the vacuole. Diffusion is a movement of particles from an area of higher to the area of lower concentration, (by random motion). Osmosis is also a special case of movement of water, from a higher to a lower water concentration across a selectively permeable cell membrane until it reaches the equilibrium. The process of osmosis makes plant cells swell up as you can see in the diagram below which shows a higher water concentration outside the turgid cell, whereas on the plasmolysed cell there is lower water concentration outside. If a lot of the water leaves the cell, the cytoplasm begins to peel away from the cell wall; this process is called plasmolysis. ...read more.

Middle

Petri dish two, 0.25M, Petri dish three, 0.50M and Petri dish 4, 0.75M, Petri dish 5,1.00M, Petri dish 6, 1.25M sugar solution. Leave all the experiment to run for 1hour 45minutes. 7. After doing all this record all the information on the table and while the experiment is running calculate the average initial weights of the potato and apple strips for each sugar concentration (molarity) and record down the data for the average initial weight. 8. After 1hour 45minutes, carefully pour out the liquid solution from all the Petri dishes but being careful that the potatoes and apple strips don't get mixed up. 9. With a paper towel remove all the extra excess liquid from each of the strips before weighing them again. Weigh each strip in the same order as the way done right at the start and then record down the data under the column of final weight. 10. Calculate the average final weight for each of the sugar solution 0.00M-1.25M. RELIABILITY OF THE RESULTS > The sizes of the all the strips must be large enough to see on difference. > Replicate experiment three times > It should be done in room temperature, because the sucrose may evaporate because it may affect the rates of osmosis. ...read more.

Conclusion

I have done the same for the potato strip result. There was also an anomalies figure in the 2.00molar sucrose concentration, which had -8.8 in the column of the percentage change in mass. Once again I have taken out this data because its anomalies from the rest of the information and doesn't fit in with them. I think that the anomalies data may have occurred, due to the amount in which the strips had weighed after it was taken out of the solutions. I have decided that it was probably because the water moved out of the strip which then became plasmalysed. The actual difference was because the mass was small which increased the error and also because of the increase in the size of the plant strip pieces. This is why I would say that the experiment wasn't exactly done in a completely fair way, there were some complications. This experiment has shown quite a variable result in replicates. To make it more accurate and avoid making the errors I could have made more concentrations for both the potato and the apple experiments, for example: - * Potato: - 0.00-0.80 molar * Apple: - 1.20-2.00 molar MORE LEFT TO ADD ON ABOUT THE EQUILIBRIUM FIND OUT WHAT IT MEANS AND EXPLAIN IN DETAIL ABOUT THE DATA USING MY PLAN SHEET. ?? ?? ?? ?? Momena Khanum Teacher: - Barry Brinklow ...read more.

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