Introduction:
To determine the biological changes that occur to potato cores over a period of time in different solutions of sucrose and to relate these changes to the phenomenon of osmosis.
Method:
We soaked several discs of potato cuted using a cork borer with around 1 centimeter of diameter and 2 milimeters of lenght into sucrose solutions with a different range of concentrations from 0 to 1.0M. Then we weighed all the potato cylinders on an electronic balance (see results) and recorded the results. We placed enough pieces of potato to cover the bottom of the petri dish and left them for 60 minutes. After this time we drained out the solutions from the petri dishes and carefully placed them in order of molarity on a paper towel.
We also measured the total mass of the discs in each solution after soaking in the solutions (see results).
Percentage change in mass of the potato is measured in each case and plotted against sucrose concentration to determine a sucrose concentration causing no change in mass. The water potential is determined from this sucrose concentration by reference to the data supplied. (see appendix A)
Results:
Conclusion
The experiment was sucessful. We obtained a large quantity of accurate results from which I was able to create informative graphs. We took enough results for the amount of concentrations that we were using, and the time that used for the experiment to last was enough to allow sufficient osmosis to occur. However if I was to repeat the experiment I might well increase the time of the result to allow more osmosis to happen and possibly find out the saturation point of the chips. The range of concentrations was adequate but I would possibly create more concentrations if I repeated the experiment so that I would have more varied results, i.e. 0.10m, 1.15m, 1.20m, and so on. This way would have allowed me to also find out the isotonic point far more accurately as the one that I estimated is very approximate.
Analysis
The trend that my graph and results show is that when the potato was placed in a solution that had a higher concentration than the chip itself, the potato lost weight (0.4, 0.6, 0.8 and 1.0 molars). In the same way when the potato chip was placed in a solution that had a lower concentration than itself, the potato chip gained weight (0.0 and 0.2 molars).
For my results I calculated the percentage gain/loss in weight using the following formulae:
Average change in weight/weight at start times 100
The graph slopes downwards. This means that the percentage gain and loss in weight and concentration are not directly proportional because the line is not straight and does not pass through the origin. However, there is a pattern on my graph, and this is, as the concentration of the solution increases, the percentage change in weight decreases.
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