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Explanation on Osmosis and diffusion:

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Introduction

Osmosis Coursework Explanation on Osmosis and diffusion: "Osmosis is the passage of water from a region of high water concentration through a semi-permeable membrane to a region of low water concentration, which will then become equal." Diffusion, although at first may seem insignificant in nature, plays quite a major part. The most obvious example would be in cells, plant and animal alike. They have partially permeable membrane in order to let in things like water, and to prevent unwanted big chemicals such as sucrose from entering. However, diffusion only takes places where there is a diffusion gradient i.e. a high concentration in one place and low in the other, moving down the diffusion gradient. Sometimes there are things which have to work against diffusion e.g. plants who need to absorb mineral ions from the soil, even though the concentration of ions is much higher in the plant that in the soil. The process of absorbing these minerals is called Active Transport. Hypothesis: Using all the evidence in the preliminary work, I predict that when distilled water is surrounding the potato after a period of time, the potato will become turgid, and therefore become, stiffened, hard and enlarged, as the water concentration in the beaker would be much higher than the water in the potato. I also predict that as more molars of sucrose solution after a certain point is used, the potato will become more flaccid, and therefore become more soft, floppy, and smaller, as the water concentration in the potato would be higher than the water concentration in the beaker. I think this will happen because the lower the concentration of water in the sucrose solution there is, the higher the water ...read more.

Middle

This factor was not easy to control, and we were not able to fully control this as we lacked the scientific equipment to do so. However, we did keep each experiment in the same room, which would roughly mean the same room temperature. ? Surface area~ the surface area effects the chips because if there is a large surface area, more surface is exposed so osmosis occurs faster. ? Type of potato~ this effects osmosis because different potatoes have different cell saps which effect the concentration. Different potatoes may absorb at different rates. That is why I will use the same potato. Apparatus: I used various apparatus for my experiment. They are listed: � Tile and scalpel - to cut the chips to size. � Test-tube rack - so the tubes do not spill solution. � Test tubes filled with solutions.; � Stopwatch - to time the experiment. � Paper towels - to dry the potato chips. � Ruler - to measure the length of the potato chips. � Potato borer - to cut potato chips out of the potato (1.4mm). � Test tubes. � Weighing scale Method � First, I'll get all my equipment together: Sucrose solution, water, potato, potato borer, scales, test tubes, Test-tube rack, ruler, scalpel, tile, stopwatch, paper towels, thermometer, measuring cylinder, and a pipettes � Next, I will measure the different concentrations of the sucrose and put 0m in the first test tube, 0.2m in the second r tube, 0.4m in the third tube, 0.6m in the fourth boiler tube, 0.8m in the fifth boiler tube, and finally, 1m in the last boiler tube. ...read more.

Conclusion

- Control the temperature. Making sure that it doesn't change. My results are probably not the best example to use to prove osmosis because of the problems that we faced, making them inaccurate and difficult to depict. However, with the problems solved the results may have shown a better idea of osmosis. - I could experiment with leaving the potatoes in for about 5 hours in order to find a smaller mass difference between each sucrose solution. - Temperature could also be changed for example the samples could be placed in different water baths and brought up to different temperatures to see if temperature played its part in the osmosis of potatoes. 5 sets of 5 potatoes could be placed in water baths at 10oC, 20oC, 30 oC, 50 oC and 60 oC. Then leave them for 24 hours making sure all the variables in the first experiment still apply however just using one molar solution. Then after 24 hours the samples would be re weighed and results recorded. I would expect that at high temperatures the potato samples would osmose the most. This is because at high temperatures the solutions water molecules would move faster and therefore equal the concentration faster. A preliminary experiment could be set up beforehand to find out how long the experiment should be kept going because if the concentration of the potatoes equalises then the weight of the potatoes will be almost exactly the same. - Other solutions could be used as well, e.g. glucose solution. I was not disappointed with my investigation because it achieved accurate results and my hypothesis was correct. Matthieu Philippe Biology Coursework Mr Robinson 01/05/2007 ...read more.

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