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To find the effect of concentration on osmosis

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Introduction

Investigation to find the effect of concentration on the effect of osmosis Aim: To find the effect of concentration on osmosis Preliminary Work: Osmosis is a specific type of diffusion. It occurs when a membrane has tiny holes in it that let water molecules pass through, but stops larger molecules like sugar. A membrane that allows only the small molecules through is called a semi permeable membrane. Therefor an impermeable membrane allows no molecules through and a permeable membrane allows all molecules through. Osmosis is where water molecules diffuse or move from an area of high water concentration to an area of low water concentration. Put simply osmosis is the diffusion of water. Diagram 1: An example of osmosis showing the movement of water molecules between adjacent cells: This diagram above shows how when the concentration of water molecules is higher than in the cell next to it they diffuse through the cell membrane. Osmosis occurs in plant and animal cells. The cell membrane of the cells is semi permeable. So if a cell containing a strong concentration of water is next to a cell with a low concentration of water, water molecules pass from the high concentration to the low concentration. In a plant cell water moves from cell to cell by osmosis. This evens out the water in a plant and helps transport water around the cells. The maximum amount of water able to be taken in by a plant cell is controlled by the cell wall, which stops the expansion of the cell and so stops it from bursting. ...read more.

Middle

The overall volumes will need to be the same to make the test a fair one so I have decided that the volumes will all add up to 30 cm�. The volumes of each test tube are shown below: 30cm� salt solution + 0cm� distilled water 25cm� salt solution + 5cm� distilled water 20cm� salt solution + 10cm� distilled water 15cm� salt solution + 15cm� distilled water 10cm� salt solution + 20cm� distilled water 5cm� salt solution + 25cm� distilled water 0cm� salt solution + 30cm� distilled water These 7 concentrations will provide me with a large enough range to produce reliable results. The test tubes will have the concentrations marked on them to prevent any mix-ups, which could lead to, inaccurate or no results for some of the concentrations. The test tubes will then have a piece of potato carefully placed within. This potato will be 3.00g in mass. In order to make the experiment fair the potatoes placed in the test tubes will all need to have the same weight and surface area. To do this they will be cut using a corer, this will ensure that they all are cylinders with the same diameter and circumference. They will then be cut into pieces 3.00g in weight using a scalpel. To make sure that they are the same weight they will all be dried carefully using a paper towel. ...read more.

Conclusion

Conclusion: I conclude that the rate of osmosis is affected by concentration. This is because of the evidence that I have found in my experiment and gathered in my research. Evaluation: I believe that the experiment I carried out went well. This is because my prediction was proved correct by my results. I believe my results to be an accurate representation of the effect of concentration on osmosis. This is because it agrees with my knowledge and research and also as I produced no anomalous results in collecting them. If I had it would be difficult to prevent due to the environment and limited resources available. However if I did produce any as stated in my method I would redo that section of tests from the beginning. To improve the experiment I would have liked to control new factors that affect osmosis. For example temperature, this would mean that I would be able to prevent some factors, which could cause anomalous results. Also I could refine the method to allow more tests and a wider range of results to back up my findings, this would help make my results more reliable There could also be more experiments carried out by different people who could then combine their result with mine to check them, as there are not the facilities at school to keep the temperature at a constant one for all experiments. I will make sure that the salt solution comes from the same batch. This is so that the concentration is the same before distilled water is added. Craig Banfield Page 1 of 3 ...read more.

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