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Osmosis Coursework

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Introduction

Osmosis Coursework Introduction For my coursework, I have been asked to look at how sucrose concentration affects Osmosis in a potato. Osmosis is the passage of a liquid from a weak solution to a more concentrated solution across a semi permeable membrane that allows passage of the solvent (water) but not the dissolved solids, from a region of high water concentration to a region of low water concentration to equalize the concentration on both sides of the membrane. The rate of diffusion is determined by the presence of other molecules and the difference in concentration. KEY Plan Equipment The apparatus that I will be using are as follows: * Potato - To take samples from with a cork borer. * 9 Test Tube's - To place sucrose solutions and potato samples in * 3 Test Tube Rack's - To hold test tubes * Sucrose Solution - To place into test tube (with potato) to see how it affects Osmosis * Scalpel - To cut potato into sections with * Scales - To record mass of potato before and after experiment * Measuring Beaker - To measure the amount of sucrose solution * Cork Borer - To obtain pieces from potato What the equipment will be used for Potato - for the Potato, 16 equal pieces of potato ...read more.

Middle

If I follow this method, I should have accurate results, will have achieved a fair test and a successful experiment. I am also going to change a factor in this experiment. To do this, I will change the concentration of the sucrose solution (step 2) I will achieve this by carrying out the method show above, but instead of using the 10cm� molar concentration, I will change this to, for example - 15cm�. Prediction Osmosis is defined as the movement of water molecules across a partially permeable membrane from a region of high water concentration, to a region of low water concentration. In a high concentration of water the amount of sucrose is low. This could be called a weak or dilute solution. In a low concentration of water the amount of sucrose is high. This could be called a strong or concentrated solution. When two such solutions are divided by a semi-permeable membrane the water will move from the area of high concentration to the area of low concentration, until both sides are equal (have reached equilibrium). I predict as the sucrose solution increases, the percentage change in mass will decrease, as more water is moving out of the potato. ...read more.

Conclusion

For the average mass change I recorded, on the graph the anomalous points are shown as they do not stay in order with the line of best fit. Interpretation of Graph The graph shows that as the sucrose molarity increases, the percentage mass change decreases, as water is moving out of the potato. Most of the results were reliable as the replicates were close to each other. This shows that osmosis has occurred. There was an anomalous result. The results were I believe that the anomalous result was the one tested at 0.2 and 1.0. There should be another replicate so that it is easier to see which the anomalous result is. I think that it is anomalous because it had small slice in it from when I removed it from the borer. This led to the chip having a larger surface area in proportion to the mass compared to the chips. Because it had a larger surface area, it would have a larger change in mass compared to the other chip. I am satisfied with the range as I was looking for the affect of osmosis in plants. However if I was to repeat the experiment I might well increase the time of the result to allow more osmosis to happen and possibly find out the saturation point of the chips. There is enough reliable evidence here to show the effects. Nicolle Caine 1 ...read more.

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Although this account has evidence of a sound understanding of the principles of osmosis, it lacks attention to detail throughout.

Marked by teacher Adam Roberts 20/05/2013

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