Does the concentration of a solution affect osmosis? -- A* - page 3
Keywords: Biology Osmosis Concentration Sucrose solution
By georgie1 on 31/12/2009
Level: GCSE Key Stage 4 (Years 10-11)
Page Number: 3 of 10 pages: 1 2 3 4 5 6 7 8 9 10
can clearly see the potato when cutting and handling.
- Blade. This is so that I can finely cut the potato so cutting is as accurately sized as possible.
- Ruler. This is to accurately measure the lengths of the potato so that all cuttings are evenly and fairly sized.
- Measuring cylinder. This is so that I can accurately measure the amount of sucrose and of water, and therefore can be definite that concentrations of each solution are accurate.
- Stopwatch. This is so that the timings of the experiment are accurately followed, and that the potato is removed from solution at the correct time. This way, experiment remains fair.
- Blotting paper. This is so that I can absorb excess water from the potato cutting so that as little water molecules as possible are initially in the potato. This gives me the lightest mass of the potato and therefore will have a firm percentage difference in mass.
- 7 medium sized test tubes. This is so hold the sucrose solution and potato cuttings.
- Tweezers. This is so that the potato cutting does not make any contact with the skin therefore no excess moisture is absorbed into the skin, affecting the mass.
- Test tube rack. This is to hold my experiment and keep all test tubes in one area.
Preliminary Experiment
Firstly, I completed a preliminary experiment to find out if there was a significant percentage difference in mass in the results, so I know if there were any factors that needed to be changed for my final investigation. I did this by carrying out a similar experiment, using only two different concentrations of sucrose solution [0.1M and 1.0M] and two potato cuttings where left to stand at room temperature for 30 – 40 minutes. The class results were as follows [my results are highlighted]:
Concentration/M Initial mass/g Final mass/g Difference/g Difference/%
0.1 2.72 2.97 0.25 9.19
My results: 0.1 3.36 3.53 0.17 5.06
0.1 3.09 3.40 0.31 10.03
0.1 3.32 3.42 0.10 3.01
0.1 3.31 3.36 0.05 1.51
0.1 3.58 3.66 0.08 2.23
0.1 3.08 3.18 0.10 3.25
Mean 0.1 3.21 3.36 0.15 4.72
Standard deviation: 3.41
Concentration/M Initial mass/g Final mass/g Difference/g Difference/%
1.0 2.97 2.46 -0.51 -17.17
My results: 1.0 3.50 3.33 -0.17 -4.86
1.0 3.25 2.83 -0.42 -12.92
1.0 3.39 3.11 -0.28 -8.26
1.0 3.35 3.10 -0.25 -7.46
1.0 2.96 2.75 -0.21 -7.09
1.0 3.10 2.90 -0.20 -6.45
Mean 1.0 3.22 2.93 -0.29 -9.06
Standard deviation: 4.32
From looking at the results table, it is clear that there is a significant difference between the results of 0.1M and 1.0M. When the values are this far apart, the differences are quite extreme and therefore it definitely seems logical to use more concentrations that have closer values e.g. 0.2M, 0.3M etc. By doing this, I will be able to show the point where the water molecules stop passing into the potato by osmosis, and start to leave. I have also clarified that I will be using a potato that is 1cm³ so that all of the experiments are fair
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