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Osmosis Investigation

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Introduction

Science coursework Osmosis Investigation Background Osmosis Osmosis is the diffusion of water only, the movement of water particles from an area of a high water concentration to an area if lower water concentration through a partially permeable membrane. Cell membranes are partially permeable because they allow water to pass through, but not others. When the diffusion gradient of water has disappeared, osmosis stops. Osmosis in plant cells Cell, in nature fluctuate between being flaccid and fully turgid. Osmosis is very important for the plants. * Helping to support a plant The vacuole of a plant cell contains cell sap, which is a solution of different solutes in water. Water therefore enters the cell sap by osmosis, and the vacuole has the appearance of blown up a balloon. This forces the cytoplasm against the cell wall. The cell is said to be 'Turgid'. If a plant is short of water, for example a pot plant which has not watered recently, the cell vacuole if 'Flaccid' and the plant wilts. * A plant root cell taking in water The vacuole of the root hair cell is more concentrated than the soil water. Water therefore enters the root by osmosis. * Controlling the stomata in leaves The size of the stomata is controlled by the guard cells which surround them. ...read more.

Middle

Step2) prepare the solutions-three for each (60cm�). Step3) dry out all the potato cubes Step4) take 5 cubes each times, weight them and record the mass (g). Step5) put them into the solution and start the timer. Step6) wait for 20 minutes Step7) pour out the solutions from each breaker. Step8) dry out the potato cubes and weight again. Record the mass (g). I will draw a result table and rewrite the results which may make them clearer to read. Find out the difference between the mass at start and the mass at finish then calculate out the average change in mass. After that, I will calculate the percentage change in mass and also find out the average of them. Later, I may use the data from average change in mass and average %change in mass to plot a graph for each data. Variables The mass of each potato cubes may be different because it is hard to keep cutting each cubes into same mass and the cell sap of them may be dissimilar because they depend on the ages of potato and where they were planted, etc. Equipment Potatoes 3 breakers Timer Water 0.2M,0.4M,0.6M,0.8M,1M solutions Knife Electrical scale Tissue paper Ruler Safety If hands are stained with solutions accidentally, then wash them immediately. ...read more.

Conclusion

* Completely dry out all potato cubes. * Weight them carefully, be ware that someone/something is affecting the electrical scale. This would improve my data because if I leave them longer in the solutions, the results will be more observable. If I cut potato into slices, they will have a large surface area. This help particles goes in and goes out more quickly, the results may be also more observable. Dry out them completely which make me do not weight the mass of surface water which could make my result anomaly, this help me to have an accurate mass of potato cubes/ slices. Careful when weighting the potato, this also makes me to an accurate mass of potato. I think my evidence is not that reliable although I have repeat each experiment for 3 times and get the average of them but I had not repeated any odd results. I might make my data more reliability if I repeat that experiment when I faced an odd result. I think the best comparison is the average change in mass but no the average percentage change in mass because the % change depends on the actual mass of potato. For addition or further work I can do is to do the experiment for more than 3 times, which may make an odd result not that easy to affect my data as I will calculate out the average. ...read more.

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