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Factors affecting Osmosis in Potato Tissue.

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Introduction

Factors affecting Osmosis in Potato Tissue Aim We are trying to find out how the mass of a piece of potato changes when placed and left in different concentrations of salt water for roughly 2 days. Preliminary work For the preliminary work, we took two small pieces of potato, placed one in distilled water and the other in 1.0M of salt concentration, leaving them for 10minutes each. And the results were as follows: Potato Salt concentration 1.0M Distilled water Before weight (g) 3.32 13.51 After weight (g) 3.13 13.90 From these results we can see that potatoes which are placed in salt water will lose weight, whilst those placed in distilled water will gain weight. These results will help me to make my prediction. Apparatus: * Potatoes * 1 mole salt water * Distilled water * Test tubes * Test tube rack * Scales * Knife * Measuring cylinder Fair Test In order to make it a fair test I will have to use the same size potato for each concentration, same amount of water, same size test tube. The concentration of the water is the input variable and the change in weight of the potato is the output variable. Method To begin with we will collect all of our equipment needed, setting up test tubes and test tube racks so we know what concentration of water to put in each. ...read more.

Middle

This process of water molecular transfer is known as osmosis. Results concentration of salt(molar) Original Mass(g) End Mass(g) Change in Weight(g) % mass change 0 3.06 3.18 0.12 9.98 0 3.05 3.54 0.49 0.2 3.05 3.21 0.16 4.58 0.2 3.07 3.19 0.12 0.4 3.01 2.62 -0.39 -14.1 0.4 2.96 2.51 -0.45 0.6 3.04 2.59 -0.45 -14.36 0.6 3.09 2.66 -0.43 0.8 3.07 2.56 -0.51 -16.19 0.8 2.98 2.51 -0.47 1 3.01 2.31 -0.7 -21.31 1 2.95 2.38 -0.57 For Graph see previous page. Conclusion From the graph and results we can see that my prediction was correct items placed in higher concentrations of salt water lost weight where as lower concentrations gained weight. As you can see I have one anomalous result which is circled. From my results we can see that the potato placed in the lower concentrations of salt water gained weight, there is a higher concentration of salt in the potato and so water moves in by osmosis, as stated in my prediction. The potato placed in the higher concentrations of water lost weight as the water had a greater concentration of salt than the potato so water moved out by osmosis. This is what I predicted what would happen; there is a net flow of water either in or out of the potato depending on the concentration of the water on the outside. ...read more.

Conclusion

For a start more accurate equipment could be used to make sure the concentrations were exactly right, the way we were doing it with measuring cylinders was very in accurate. Temperature is a problem that could have occurred with our experiment as our test tubes were carried across to the opposite building. The test tubes in the middle may have stayed warm where as the ones on the outside may have lost heat. A way to overcome this would be to use an incubator to keep test tubes at a constant temperature. The potato pieces were generally the same size in my experiment but it could have been made more accurate by having more accurate size potatoes, this could be achieved with the use of better scales. Within our experiment we could have provided further evidence by testing the potatoes at different concentrations. For example instead of testing at 0.2M then 0.4M etc we could have tested at 0.1M then 0.2M and so on, this would have given us much more accurate results. The experiment could have been extended in many different ways some of which may have been to test the effect of temperature in osmosis or the effect on osmotic potential using sugar concentrations rather than salt concentrations. Also we could have looked at the osmotic potential of different vegetables and compared them all, this would have given us a much better understanding of osmosis. Robert Bentham Candidate No. 9318 Centre No. 16327 ...read more.

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