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Osmosis Coursework

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Introduction

OSMOSIS COURSEWORK INFORMATION Diffusion Diffusion is the movement of molecules of a substance from an area where they are in higher concentration to one where their concentration is lower. Where the concentration of a solute is low, the concentration of the solvent will be high, so it's molecules will move the other way until the concentration is equal. SOLUTES are dissolved in a fluid - A SOLVENT, which is normally water. Many substances such as oxygen and carbon dioxide diffuse in to and out of cells. This is an example of how diffusion balances the molecules. The mixture reaches a state of equilibrium, in which the molecules of both substances are evenly mixed in the container The rate of diffusion depends on how heavy the molecules are. Heavy molecules diffuse more slowly than light molecules. Diffusion of matter occurs most rapidly in gases, more slowly in liquids, and most slowly in solids. The spreading of a smell throughout a room is a common example of gaseous diffusion. A solid may dissolve and diffuse through a liquid, as when a lump of sugar is placed in a cup of water. ...read more.

Middle

* 8 different sugar water concentrations METHOD We used 8 different concentrations of sugar solution in the experiment and each of the 100cm� of 8 concentrations were put into 5 test tubes. We then cut 40 potato lengths each measuring 10 mm and put 1 potato cylinder in each of the 40 test tubes. We left the potato in the test tubes for 30 minutes then emptied the solutions and measured all of the cylinders. Then we measured the new lengths accurately with a ruler. We wrote down all of the results clearly. For safety, we were very careful with all the glass wear. We were also careful with the sharp implements such as the knife by keeping fingers and thumbs away from the blade whilst cutting. To make this a fair test we cut all of the potato cylinders the same length used the same amount of liquid in the test tubes, left the potato samples in the liquids for the same amount of time (30 minutes) so that osmosis had the same amount of time to take place in every variant of concentration and we also measured the cylinders accurately with the same ruler each time. ...read more.

Conclusion

The strongest solution, 10% sugar water solution had an average of 11.2mm. This should have been the longest average, as osmosis should have taken the biggest effect on this solution. Almost none of these results follow the hypothesis I made - the increases in length were not even in order. The results did not show many consistencies relating to any facts about osmosis or diffusion. I think this is either because we didn't measure the potato cylinders properly before the experiment, the sugar water solutions were not very accurate in the amount of sugar in the test tubes or we did not measure the cylinders accurately after the experiment. The most likely explanation is human error in the measuring or the cylinder samples because we managed to control all of the solution variables and kept them constant and fair. To avoid mistakes such as measuring the potato wrong we should have double-checked the lengths before and after osmosis had taken place. This experiment was not successful because the aim was not fulfilled - the results did not back up or prove the facts that are known to me about osmosis and diffusion. If I had more time I would have repeated the whole experiment again, measuring the potato cylinders and the percentage of sugar water solution more accurately. ...read more.

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