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investigate the effect of osmosis on pieces of potato in different concentrations of sucrose solution.

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Introduction

Biology Coursework - Year 11 Osmosis Investigation Planning Aim To investigate the effect of osmosis on pieces of potato in different concentrations of sucrose solution. Apparatus 6 Petri dishes Marker pen Beakers Stop clock Cutting tile Knife 25cm3 Measuring Cylinder Distilled water 1.0 Molar solution of sucrose Potatoes Tissue paper Mass balance Plan The factors that affect the volume of water taken in by the potato are: o The concentration of the sucrose solution that they are placed in o The size of the potato o The time the potato is left in the solution Before we started the experiment some preliminary work was done to establish the appropriate size of the potato pieces and the duration of time they were to be left in the solution. To ascertain the size of the potatoes we were to use various sizes of potato were put into the petri dish at different times, water was poured onto them until the piece investigated was completely covered. The size of the biggest piece of potato that was covered, but without the water overflowing the rim of the petri dish, was chosen to be the correct size. We found that 1cm x 3cm x 3cm was the best size. To determine the duration of time to leave the potato pieces in the solution we first placed a piece of potato in a solution of 0.5molar sucrose solution which was left for 10 minutes. ...read more.

Middle

The length of time the anyone potato piece is in the solution is 20 hours. 2) The volume of solution in the petri dish is always the same 3) The measurement of the potato is always the same 4) The potato is always skinless Obtaining Evidence After steadily changing the concentration of the sucrose solution I found out the following results before repeating the experiment another time. A Table To Show the Change in Mass of Potatoes in Different Concentrations of Sucrose Solutions for the first experiment Concentration (mol) Mass before Mass after % gain/loss 0.00 9.44 10.68 13.14 0.25 10.45 10.65 1.91 0.50 10.28 8.77 -14.69 0.75 8.70 6.60 -24.13 1.00 11.44 8.31 -27.36 A Table To Show the Change in Mass of Potatoes in Different Concentrations of Sucrose Solutions for the second experiment Concentration (mol) Mass before Mass after % gain/loss 0.00 11.00 12.17 10.64 0.25 11.21 10.84 -3.30 0.50 10.70 9.67 -9.63 0.75 10.11 7.73 -23.54 1.00 7.78 8.32 6.94 For the next table I calculated the averages of the change in mass of potatoes in different concentration of sucrose solution of the first two experiments. However, when working out the averages I did not include the anomalies. An anomaly is something that you do not expect; an irregularity. A Table To Show the Change in Mass of Potatoes in Different Concentrations of Sucrose Solutions for the average of the two experiments Concentration (mol) ...read more.

Conclusion

These are called anomalies. I could have obtained better results if I had performed more experiments, to do this I would have needed more time; more tests would have made the average more accurate. With more time I could have experimented with more concentrations. With these extra concentrations a trend in the results would be easier to see. If a microscope was used to view the potato cells after each experiment we may have noticed if the cells were either plasmolysed or had under gone lysis. As you can see the experiments were repeated twice, each time the results are similar. This should show that they are reliable enough to make a firm conclusion. There are a number of alterations that would allow us to investigate further into osmosis. o Test how different semi-permeable membranes could effect osmosis. This could be done by using other organisms instead of a potato. o Investigate the concentration at which the potatoes will undergo plasmolysis. o Investigate how changing surface area of the potato pieces and different volumes of solution affect the rate of osmosis. o Investigate what affect temperature has on osmosis o Investigate what affect sunlight has on osmosis o Investigate the size of the pieces of potato that osmosis occurred most rapidly o Investigate how long the poato piece had to be in a certain solution before it plasmolysed o Investigate how long the poato piece had to be in a certain solution before it under went lysis ...read more.

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