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the effect of osmosis on a potato chip

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Introduction

This is a report into an investigation done in January/February 2007. It is a piece of Biology Coursework looking into how osmosis affects a potato chip. In this case study I will be looking at how osmosis affects a potato chip. My aim is too investigate the effect of varying concentrations of certain salt solutions, and water, on the amount of osmotic activity between the solution and a potato chip of a given size and mass. Osmosis Osmosis is the movement of a solvent, usually water, through a semi-permeable membrane (the semi-permeable membrane only being permeable to the solvent). The solvent moves from a low concentration (hypotonic solution) to high concentration (hypertonic solution). Ignoring factors such as osmotic pressure, the process only stops once the concentrations are balanced on both sides of the semi-permeable membrane. Low concentration High concentration > Lots of water molecules Few water molecules The cell walls of plants have semi-permeable membranes. This allow osmosis to occur in samples of plant material e.g. potato. 1. If the medium surrounding the cell has a higher water concentration than the cell, the cell will gain water through osmosis. Such a solution is called a hypotonic solution. 2. If the medium has exactly the same water concentration, there will be no net movement of water across the cell membrane. ...read more.

Middle

I place a peeled potato chip into a beaker of 5 moldm-3 salt solution. I then left it for 24 hours and I weighed the chip before and after my short test. I found out that osmosis had indeed taken place and I should then continue with my final experiment as planned. Results Concentration of salt solution (Moldm-3) Test/sample 1 Test/sample 2 Test/sample 3 Mass of potato chips (g) Before After Before After Before After 0.0 (water) 2.09 2.69 2.08 2.50 2.04 2.55 1.0 2.10 2.30 2.05 2.22 2.08 2.41 2.0 2.05 2.20 2.00 2.25 2.11 2.19 3.0 2.09 2.01 2.04 2.10 2.01 2.00 4.0 1.98 2.00 2.08 2.01 2.07 2.00 5.0 2.05 1.45 2.02 1.20 2.00 1.50 Concentration of salt solution (Moldm-3) Test/sample 1 Test/sample 2 Test/sample 3 Average Change in mass (g) Total mass change (delta) in grams(g) 0.0 (water) +0.60 +0.42 +0.41 +0.47 1.0 +0.20 +0.17 +0.33 +0.23 2.0 +0.15 +0.25 +0.08 +0.16 3.0 -0.08 +0.06 -0.01 -0.01 4.0 +0.02 -0.07 -0.07 -0.04 5.0 -0.50 -0.83 -0.50 -0.61 Sample 1 Sample 2 Sample 3 Salt solution Percentage mass change Average percentage mass change 0 +28.7081 +20.1923 +25.0 +24.6 1 +9.5238 +8.2927 +15.8654 +11.2 2 +7.3171 +12.5 +3.7915 +7.86 3 -3.828 +2.9412 -0.498 +2.42 4 +1.0101 -3.365 -3.382 -1.91 5 -29.268 -40.594 -25.0 -31.6 Analysis The potato chips that were left in pure water gained an average percentage change in mass of +24.6. ...read more.

Conclusion

I might also have carried out more tests on each solution to get more accurate data. If I wanted to explore osmosis further then I would do the experiment using more moldm-3's, instead of using 1,2,3,4,5 I would go up in 0.5's. e.g. 1.0,1.5,2.0,2.5,3.0,3.5,4.0,4.5,5.0. This would also help to investigate the concentration of the potatoes'. The weighing of the potatoes was another area in which I think that I could have improved my experiment, the scales that I used were only 0.00g but I would have used 0.0000g if I had had the opportunity. All of this would improve the data that I could analyse and would provide me with a more accurate graph with which to use. Safety Precautions The experiment that I did was not a very dangerous one, but I still had to consider some safety precautions. I wore Goggles during the whole of my test in case any liquid was released from any of my samples, this was of utmost importance when I was using the apple corer to cut the potato. This presented another hazard. Whilst cutting the potatoes using the apple corer I had to be extra careful not to exert too much pressure and I had to keep my fingers well out of the way. These were the only real safety precautions that I had to take because it was a relatively safe experiment to perform. Osmosis Coursework David Locke ...read more.

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