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To investigate the effect that a varied concentration of solution has on the osmotic activity between the solution and potato cylinders.

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Introduction

G.c.s.e Coursework: Osmosis Aim: To investigate the effect that a varied concentration of solution has on the osmotic activity between the solution and potato cylinders. Hypothesis: Osmosis is a special type of diffusion. It occurs in plants when a weak solution is separated from a stronger one by a semi-permeable membrane, such as a cell wall. Water always flows from the weak solution to the strong one. This then dilutes the strong solution. This process is what moves water throughout the cells of the plant. The membrane has small holes, which only allow smaller molecules to pass through, such as water molecules, but blocks larger molecules, such as sugar molecules. This process continues until the molecules reaches an area of equilibrium. This means that the molecules are distributed evenly throughout the object, meaning that there is no higher or lower concentration. This water is than lost through the plants leaves as water vapour, known as transpiration. I predict that for this experiment that a potato in a lower concentration of solution will increase in mass more than a potato in a high concentration of solution. ...read more.

Middle

We then label each test tube with what concentration it holds i.e. 0.2, 0.4 etc. We then drop 6 of the potato cylinders into each test tube, making sure we know what the weight of the potato was before we put them in. We then leave the strips in the test tubes for exactly 20 minutes. After the 20 minutes have elapsed, we remove the potatoes from the test tubes and place them on a piece of tissue paper. We dry of the potatoes removing any excess solution. As soon as we remove the potato strips from the solutions, the osmotic activity stops. After the potato cylinders have been wiped down, we measure them again using the electronic scales. We then note the new weight of each potato cylinder. After we recorded the weight of the cylinders, we repeated the whole experiment again under the exact same conditions using the leftover 6 cylinders. This way the results are more accurate. Precautions: Throughout the experiment, there were a few things that could not be changed. These precautions must be taken to ensure that the experiment stays fair. ...read more.

Conclusion

This shows that my theory, that a potato in a higher concentration will experience less osmotic activity than a potato in a low concentrate solution was correct. Evaluation: I think my experiment was a success because it allowed me to obtain a large quantity of results that I then used to produce a set of graphs and tables. They show my theory was correct and that osmosis is affected by concentration. The only factor that I was not very happy about was the way that I had to cut the potatoes. The borer was very unreliable and the size and diameter of the potato cylinders were not always the same. One way which I could improve this experiment is by increasing the time in which I left the potatoes in the test tube. I think a longer time would have allowed for more activity and possibly more accurate results. Also, if there was a more accurate process to produce the cylinders I definitely use that way. The final way that I think I could improve this coursework is by using more varied concentrations of sucrose solution such as 0.15, 0.25 etc. ...read more.

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