Does the concentration of a solution affect osmosis? -- A* - page 7
Keywords: Biology Osmosis Concentration Sucrose solution
By georgie1 on 31/12/2009
Level: GCSE Key Stage 4 (Years 10-11)
Page Number: 7 of 10 pages: 1 2 3 4 5 6 7 8 9 10
believe that the percentage difference in mass for the experiments that were left to stand for 48 hours is close to being directly proportional to the concentration of the sucrose solution [percentage difference in mass α concentration of sucrose solution]. I think this is true because the line of best fit is generally quite straight, up until approximately 0.8M. From 0.8M to 1.0M, the line of best fit has a much more significant curve and therefore it is likely that it is near this point that the percentage difference in mass has began to decrease less rapidly, as it nears an equilibrium.
Both curved lines of best fit fall between all of the error bars and pass closely to average results. Although the error bars have quite a large range, they all tend to be evenly spaced and of similar height. This shows me that all of the results have been recorded in the same way, and that additional factors have been maintained throughout. This means that my experiment is reliable in terms of consistency. The only error bar that is a lot larger than the rest, and even did not fit onto the graph, was for my 48 hour reading of a 1.0M concentration. It shows that the highest and lowest values of percentage difference in mass were extremely widespread. This could be because the potato cutting was not blotted effectively at the beginning of the experiment and therefore there would already be more water molecules in the cutting than necessary. It could also be than the potato cutting was not cut to the agreed size [1cm³], allowing more surface area for the process of osmosis to occur. It is not likely that the temperature of the room affected the osmosis, because it would have had the same impact on all of the results; which has not happened. However, one of the test tubes may have been more exposed to the effects of a heater than others, adding a limitation.
I can see the potato cuttings that gained water by osmosis during this experiment began the experiment at a lower water potential than the solution, and vice versa. The graph shows that the potato cutting decreased much more in mass when left to stand for a 48 hour period, whereas there was a little increase. This suggests that when plasmolysis occurs [when cells lose water], it continues to happen for
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