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Investigation into Osmosis.

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Introduction

Investigation into Osmosis in Potato Cylinders. Planning I am investigating the effect of osmosis on a potato. Osmosis is the diffusion of water down a concentration gradient through a semi permeable membrane. I am investigating the effect of water concentration on the potato cylinders. This means that I will put potato cylinders into salt solutions of different concentrations. Factors - Size of cylinder - Volume of solution potato is in - Time left in solution - Surface area of potato cylinder If I am going to make this a fair test, then I will have to control these other factors. The size of the potato is very important. This is because if the size of the potato varies, so will the amount of mass it can loose or gain. I am going to try to cut all the pieces of potatoes, to the same size. To ensure this I will use a cork borer. I will have cylinders with the same width and height, but the length of the cylinders will differ. ...read more.

Middle

For this experiment I am going to use the same potato. The time the potato cylinder is left in the solution must be kept the same for each cylinder. This is because more or less solution may be absorbed depending on time. I am going to keep each potato cylinder in each solution for nine days. The surface area of the potato cylinders will be kept the same by having all the cylinders the same size. This must be kept the same because the amount of surface area exposed to the solution may effect the rate of osmosis. The thickness of the cylinder will already be the same, so I will cut the length of each cylinder to 3cm long. To make the mass readings more fair, I will take each cylinder, roll the cylinder gently on a paper towel, to remove all excess solution, and I must not squeeze the cylinder. I am also going to use the same balance to weigh my cylinders. ...read more.

Conclusion

The potato cylinders will be carefully cut on a white tile using a scalpel, so that no one will be cut. My experiment is not testing how permeable the cylinder's membrane is, but it is testing the rate of osmosis of the salt solution. I am predicting that the higher the concentration that the cylinder is exposed to, the more water will move out of the cylinder; making it flaccid. I am going to set up the experiment so I have three results per concentration, I will then take an average to make the test fairer. Apparatus The apparatus I am going to use will be: - A cork borer - A white tile - A scalpel - 10 boiling tubes - A large beaker - A measuring cylinder - A large potato - Salt - Water - Weighing scales Diagram Results Concentration (%) Initial mass Average Initial Length Average Final Mass Average Final Length Average Change in Mass Change in Length 0 1.82 3 0.57 1.56 -1.25 -1.44 2 1.74 3 1.04 2.3 -0.7 -0.7 5 1.80 3 3.98 2.8 +2.18 -0.2 10 1.75 3 4.83 2.83 +3.08 -0.17 20 1.80 3 4.99 3.03 +3.19 +0.03 Kay Bromley P3 ...read more.

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