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Osmosis in Potatoes.

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Introduction

Osmosis in Potatoes Osmosis is a special type of diffusion where water moves across a semi permeable membrane from an area of low solute concentrating to an area of high solute concentrating. Osmosis is an important in plant cells as it makes the cell turgid. Turgidity is when no more water can enter the cell and therefore helps to keep the plant firm and upright. Variables: Some parts of the experiment will have to be kept the same while one key variable is changed. Some of the variables I am going to control are: * Time left in solution - If the chips were left longer in the solution than others, more time would be allowed for osmosis to occur. * Surface area of potato chip - If the surface areas are larger on some chips than others there would be larger and there would therefore be more space for osmosis to happen. I have chosen to change the concentration of the sugar solution. If any of the non-variables aren't kept constant it would mean it would not be a fair test. ...read more.

Middle

so we could easily work out the percentage of liquid. 6. We then placed three of the potato chips into each of the test tubes and put a bung on top. 7. We left the chips in the concentration for 24 hours for the osmosis to occur. 8. The next day we emptied the test tubes in a sieve and measured each chip from each solution. Prediction: I believe that the more Sucrose solution present in the test tube the smaller the chip will be. This is because water diffuses from the chip through the semi permeable membrane and into the sucrose solution because it has a lower concentration of water. So when loads of the water has diffused from the chip it will shrink and will no longer be turgid instead it will become flaccid. Flaccid is the exact opposite of "turgid", instead of the cell-becoming firm it becomes soft and limp. Aim The aim of this experiment is to investigate the movement of water into and out of plant cells by osmosis. ...read more.

Conclusion

This is because the cell is fully turgid and no more water can enter it. At point B (100% Concentration of Sucrose Solution), the cell is not decreasing any further in size. This is because the cell is fully plasmolysed and no more water can leave the cell. (Plasmolysed is when a plant cell loses water and the vacuole shrinks. The cytoplasm and membrane shrink away from the cell wall. This is a plasmolysed cell.) Evaluation: The results we got from the experiment were reliable and fitted a clear pattern. Though I believe if we were to have done the experiment again with more chips and a bigger variety of dilutions like 10%, 20%, 30%, 40% etc. then we could have got more exact results. Also when controlling variables if we had controlled the temperature then the experiment would have less chance of mistakes and anomalies, as having a different temperature in one test tube than another will change the rate of osmosis. When measuring the chips we could have got more exact results by using a Vernier Calliper as this measures to the closest 0.1mm and would therefore give a more accurate measurement giving us more exact results. ...read more.

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