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Investigate the effect of surface area on osmosis in potato tissue.

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Introduction

To investigate the effect of surface area on osmosis in potato tissue Hypothesis: The larger the surface area of the potato, the quicker osmosis will take place and the larger the mass will be at the end of the experiment, therefore the difference in mass of the potatoes from the start of the experiment to the end of the experiment will be larger. The potato pieces, which are left in the sucrose solution, will decrease in mass and the pieces of potato, which are left in water, will increase in mass. Theory: Osmosis: The diffusion of water through a partially permeable membrane, from a high concentration of water to a low concentration of water until the concentration is equal. As cell membranes are permeable they allow certain molecules to pass through them, such as water (H2O), through tiny holes in the membrane. These molecules contribute to the contents of the plasma around the vacuole of the cell. Although the membrane is permeable to some molecules, others are too big to fit through the tiny holes in the membrane, therefore they cannot take part in osmosis. The larger the surface area, the more cells are directly exposed to the liquid, therefore more water can transfer through the membranes of the cells at one time, therefore, because water has entered the cells, they will increase in mass. ...read more.

Middle

Weigh all the pieces of potato after they have been drained of excess liquid by means of patting dry with an absorbent towel, being careful to keep the pieces separate from each solution to avoid confusion, record the results. 8. Find out the mass change of the pieces of potato by subtracting the mass afterwards from the mass beforehand. Record the results. Measurements: * I will measure the surface area by using an accurate ruler when cutting the pieces of potato. * I will measure the mass of the potato by weighing it after the potato has been left in the solution for 90 mins. * I will measure the time the potatoes are left in the beakers by using a stopwatch, once the time has got to 90 mins, I will take the potatoes out of the beakers and dry them before weighing them. Fairness Precautions: * Make sure the amount of liquid in each of the beakers are exact so that a piece of potato doesn't have more water to transfer into the cell, therefore making the mass heavier and the results wrong. * Make sure the blocks of potato are cut with the precise measurements to let the surface area be exact otherwise either more or less water can be transferred at the one time depending on the actual measurements of the pieces. ...read more.

Conclusion

To make the experiment even more accurate I could have suspended the potato pieces in the solution to make it certain that all of the surfaces were exposed to the liquid without excluding the base. This would have given me better results because the surface area played a main part in the experiment and the sides that were excluded would have made a difference in the results I obtained. I could have also used more surface areas to make the experiment even more accurate. For example, I could have cut more pieces of potato to give surface areas of 26cm2, 26cm2, 30cm2, 38cm2, 42cm2, 44cm2 and 46cm2 to fill the gaps on the graph which hopefully would have given more of a pattern to the graph. To extend this work I would try different concentrations of sucrose with different surface areas to look at any patterns which might emerge there, I would also repeat the experiment and measure the amount of liquid left in the beakers at the end of the experiment. I also think it would have been useful to repeat the experiment another time and make more replicates to try and get the average results instead of only having one set of results to follow. It is possible that my results were wrong because of a fault in my method or the apparatus I used, but it is unlikely as the results I collected were close to the results I predicted. Biology Coursework Yr10 Tracy Kelly ...read more.

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Here's what a teacher thought of this essay

4 star(s)

****Overall a well planned and carried out experiment which needed a little more depth in the planning section. The inclusion of selected references to inform the plan would be helpful.
To improve:
Planning was well carried out with a trial experiment. The prediction could be made clearer. If the prediction could be made quantitative ( perhaps by doing some background research) this would be helpful.
Obtaining results: The student carried out a trial experiment and a good range of the independent variable with a fair number of repeats. The student should try to ensure all units and concentrations are clearly recorded.
Analysing Evidence and Evaluation: The graph was not available to view. The student needed to explain the extent to which the conclusion supported the prediction and look at ways of improving the reliability of the evidence. The student has tried to account for the anomalies mentioned but the suggestions for further work are a little limited.

Marked by teacher Stevie Fleming 29/05/2013

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