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Discover what effect water with different NaCl concentrations have on potatoes, and find out whether high salt content in water has a better, worse, or the same effect on potatoes in comparison to lower molarity water (less salt).

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Introduction

THE SCENARIO Freak weather conditions and a particularly high tide resulted in land above the Thames Barrier being flooded with estuarine waters (these have a high salt content relative to rain water). The Port of London authority have received a writ from a farmer. He claims that their failure to close the Thames Barrier has resulted in damage to his potato crop: the potatoes became soft and spongy and were no longer fit for human consumption. AIM To discover what effect water with different NaCl concentrations have on potatoes, and find out whether high salt content in water has a better, worse, or the same effect on potatoes in comparison to lower molarity water (less salt). The point of this is to investigate the farmers claim and discover whether he has a strong case. I will be investigating using six different water molarities: 0, 0.2, 0.4, 0.6, 0.8, and 1 BACKGROUND INFORMATION ON OSMOSIS Osmosis is the movement of water molecules from an area of high concentration to an area of low concentration through a semi-permeable membrane. Osmosis is the movement of water, unlike diffusion, which can also occur in gases. This is different to simple diffusion because it does not involve a permeable membrane. It is a passive process, meaning that it does not require energy, unlike active transport. Diffusion is also a passive process. It is the natural tendency for particles in liquids or gases to move from an area of high concentration to an area of low concentration. The plant cells take in and give out water through their permeable membrane. If the solution is hypotonic to the cell, water moves into the plant cell vacuole, and pushes against the cell wall. This is what makes the cell turgid. The cell wall stops the cell from bursting. Animal cells don't have a cell wall so they may burst if too much water enters them. ...read more.

Middle

You could just put the chip in front of the beaker that you got it from. 16. Leave the chips to dry. 17. Weigh the chips again, take note of weight in "weight after" section of the results table, and using calculator, calculate change in mass, and % change, and write them on the results table. 18. Pack away equipment and throw chips away. 19. If you have time, you may want to repeat the experiment again for accuracy. RESULTS TABLES INDIVIDULE The experiment can be repeated up to 3 times. Molarity 0 0.2 Attempt 1 2 3 1 2 3 Mass before Mass after Change in mass % change Molarity 0.4 0.6 Attempt 1 2 3 1 2 3 Mass before Mass after Change in mass % change Molarity 0.8 1 Attempt 1 2 3 1 2 3 Mass before Mass after Change in mass % change AVERAGE To work out the average I will add all of the results for that molarity up, and divide it by the number of results. Molarity 0 0.2 0.4 0.6 0.8 1 Mass before Mass after Change in mass % change RESULTS GRAPH RESULTS TABLE Molarity 0 0.2 Attempt 1 2 3 1 2 3 Mass before (g) 2.75 2.52 2.72 2.52 2.54 2.62 Mass after (g) 3.14 2.88 3.1 2.45 2.43 2.53 Change in mass (g) .39 .36 .38 -.07 -0.11 -.09 % change 14.2 14.3 14.0 -2.8 -4.3 -3.4 Molarity 0.4 0.6 Attempt 1 2 3 1 2 3 Mass before (g) 2.56 2.43 2.48 2.6 2.62 2.57 Mass after (g) 1.89 1.8 1.88 1.94 1.92 1.85 Change in mass (g) -0.67 -0.63 -0.6 -.66 -.7 -.72 % change -26.2 -25.9 -24.2 -25.4 -26.7 -28.0 Molarity 0.8 1 Attempt 1 2 3 1 2 3 Mass before (g) 2.57 2.58 2.45 2.43 2.79 2.62 Mass after (g) 2.08 1.97 1.96 1.88 2.25 2.13 Change in mass (g) ...read more.

Conclusion

In general, the results follow what I had predicted, and I now have evidence to back the farmer's case. To see whether the farmer was correct in thinking that the higher molarity water was the cause of his potato crops doing badly, you would need to find out the molarity of the estuarine water. If the water is 0.17 mol or below, then the estuarine water had a good effect on the potatoes. If the water is higher than 0.17 then the farmer is correct and deserves compensation. FURTHER EXPERIMENTS What further experiments could I do? I could repeat this experiment for further accuracy. I did this experiment in the winter, in cold conditions, so I could do it in the summer to see what effect temperature has on it. For further accuracy I could put a number of the experiments under a different, set temperatures. Warmer temperatures usually speed up reactions, so for this experiment I would predict that the warmer it was, the quicker the mass would change. I could also see whether using old potatoes had a different effect than using new potatoes, or using the skin had different results than using the centre of the potato. I could find the exact isotonic point by using molarities nearer to 0.17. For example I could do: 0.16, 0.165, 0.17, 0.175, 0.18, 0.185. I could try it on a different pH food, rather than potatoes, or use sugar instead of salt. I could also change the surface area of the chip, or the amount of solution put into the test tube. I could leave the experiment for different amounts of time, e.g. 30 mins, 1 hours, 2 hours, 4 hours, 8 hours, 24 hours, and see what effect that had on it. I think that at first there would not be a large percentage change as it would not have had enough time for the movement of water molecules to take place. Eventually the graph would level off. I could use a different amount of molarity solution. For example I could see what difference there was using less or more than 20ml. ...read more.

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