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Osmosis, I predict the mass of potato will first increase then start decreasing as the concentration of salt increases. I think this because at first water will enter the potato

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Introduction

OSMOSIS COURSEWORK OSMOSIS Aim: To investigate the effect of different concentrations of salt solutions on the mass of potato tissue. Background Information: Osmosis Some membranes allow some particles to pass through them and not others, they are partially permeable. Osmosis is a special type of diffusion - diffusion of water molecules through a partially permeable membrane. More water molecules pass from the water into the dilute solution than pass back the other way, because there is a higher concentration of water molecules in the pure water than there is in the solution. Eventually the level on the more concentrated side of the membrane will rise, while that on the less concentrated side falls. When the concentration of water is the same on both sides of the membrane, the movement of water will be the same in both directions. Osmosis in plants Plant cells have a strong cell wall surrounding them. When they take up water by osmosis they start to swell, but the cell wall prevents them from bursting. Plant cells become "turgid" when they are put in dilute solutions. Turgidity is very important to plants because this is what makes stand up into the sunlight. When plant cells are placed in concentrated sugar solutions they lose water by osmosis and they become "flaccid. ...read more.

Middle

I am happy with my results in the preliminary test. The preliminary test helped me inform my plan by giving me an idea how the experiment will be like and give expected results. Results: Test 1 Concentration of salt solution M 0 0.2 0.4 0.6 0.8 1.0 Mass before of potato cylinders (g) 0.99 1.02 0.98 1.01 1.01 1.01 Mass after of potato cylinders (g) 1.01 0.81 0.71 0.67 0.65 0.64 Change in mass of potato cylinders (g) +0.02 -0.21 -0.27 -0.34 -0.36 -0.37 Test 2 Concentration of salt solution M 0 0.2 0.4 0.6 0.8 1.0 Mass before of potato cylinders (g) 0.98 0.96 1.00 0.98 1.03 0.97 Mass after of potato cylinders (g) 1.05 0.85 0.76 0.66 0.62 0.61 Change in mass of potato cylinders (g) +0.07 -0.11 -0.24 -0.32 -0.41 -0.36 Test 3 Concentration of salt solution M 0 0.2 0.4 0.6 0.8 1.0 Mass before of potato cylinders (g) 1.04 0.93 1.05 0.99 0.99 0.98 Mass after of potato cylinders (g) 1.06 0.82 0.77 0.66 0.62 0.64 Change in mass of potato cylinders (g) +0.02 -0.11 -0.28 -0.33 -0.37 -0.34 Average results: Concentration of salt solution M Average mass before of potato cylinders (g) Average change in mass of potato cylinders (g) Average percentage change of mass (%) ...read more.

Conclusion

This would be because it increases in mass from the last point that was at a lower concentration. I think my results are still valid because I believe that it is a very small fluctuation in the graph. To increase accuracy I could do the experiment few more times and find the average of the results also I rounded my values up which would make my results less accurate. I can see from looking back to my method that some of my equipment could be improved to increase accuracy. For example I could have used burettes as they are a very accurate way to measure. Also I could use more accurate scales to measure the weight of the potato cylinders. The reliability of evidence for my work is very valid and I believe it is sufficient to support my conclusion. The preliminary test was very strange that its results where very different from all my other results. I think it could be to do with the potato or the equipment, as we did the preliminary test and the other tests on different days using different equipment. If I could take this investigation further, it would be to investigate active transport in plants. Active transport is the process by which dissolved molecules move across a cell membrane from a lower to a higher concentration. In active transport, it requires an input of energy from the cell. ...read more.

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