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Osmosis in Potatoes.

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Introduction

Osmosis in Potatoes Planning This experiment will use osmosis to estimate the concentration of sugar in a potato. Osmosis is diffusion (The movement of molecules from one concentration to another) of a solution across a semi-permeable membrane. Osmosis is different to osmosis because a semi-permeable membrane will only let small molecules like water through. I will put a potato core in a certain concentration of sugar solution. If the concentration of sugar is greater outside the potato then diffusion will try to level the concentration of sugar. However sugar cannot move through a semi-permeable membrane so water will move from the potato to the sugar concentration making the potato core flaccid. If the concentration is greater in the potato then water will move from the solution to the potato making it turgid. Therefore I predict that the potato will get bigger in a low concentration and smaller in a high concentration. I can measure the amount of water that has moved by weighing the potato before and after the experiment and calculating the difference. If I plot a graph of my results I will be able to find out when the potato does not increase or decrease in mass therefore finding the concentration of sugar in a potato. In my experiment I will firstly get a potato core and weigh it. ...read more.

Middle

I predict that the concentration of potato will be approximately 0.3% as my preliminary experiments show there was a bigger change in concentrated sugar solution then water. I also predict that this experiment will produce a straight line as osmosis will continuously happen. Obtaining Evidence Test 1 Test 2 Test 3 Sugar Start End Start End Start End Concentration Mass (g) Mass (g) Difference Mass (g) Mass (g) Difference Mass (g) Mass (g) Difference 0.0% 1.25 1.45 16.0% 1.65 1.85 12.1% 1.60 2.00 25.0% 0.2% 1.25 1.27 01.6% 1.65 1.76 06.7% 1.60 1.99 24.4% 0.4% 1.25 1.13 -09.6% 1.65 1.57 -04.8% 1.60 1.43 -10.6% 0.6% 1.25 0.90 -28.0% 1.65 1.17 -29.1% 1.60 1.14 -28.8% 0.8% 1.25 0.79 -36.8% 1.65 1.16 -29.7% 1.60 1.04 -35.0% 1.0% 1.25 0.89 -28.8% 1.65 1.03 -37.6% 1.60 1.04 -35.0% Immediately I noticed that in high concentrations the cores floated because the solution was thicker but this is unlikely to of affected our results. When taking my results I found that the cores in the high concentration of sugar had made a very sticky and thick solution. This was probably because starch form the potato had got into the solution. The thick solution caused a problem as when weighing the potatoes at the end needed to be drained and draining to different standards may have caused some unfair results so I tried to get as much of the solution as I could off. ...read more.

Conclusion

I could improve my method by using more accurate measuring instruments. If I had more time I would of also repeated more tests and used a wider range of concentrations. After reviewing my results I could go back and look more in depth at concentrations close to my approximate concentration to get a more accurate result. I could also change the time I leave the experiment for as if I leave it for longer there is more likely to be a clearer result. Error in my investigation could have been caused by many variables and reducing the amount of errors will produce clearer and precise results. One error is that it is hard to find the mass of a potato if it has a layer of thick solution around it which could be got rid of by drying the outside of the potato with a paper towel. Another error is the inaccuracy of measuring devices which can be solved through more accurate measuring devices. Osmosis is also not very accurate as it does not select the concentration it levels. So water will be distilled into the potato to level the concentration of sugar as well as other concentrations such as starch. This will not affect the shape of the graph but it will mean the concentration of sugar in potato is less than what I have found. Peter Luetchford Science GCSE Biology Coursework 02/05/2007 Page 1 ...read more.

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