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Chip Shop Coursework - Osmosis.

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Introduction

Chip Shop Coursework Planning Introduction Mr. and Mrs. Brown own a fish and chip shop; they employ Lee for an hour after school every day to prepare the chips, which are to be fried during the evening. Lee peels the potatoes, cuts them into chips and then places them in containers of salty water to prevent them from drying up. There have been complaints that the chips are sometimes soft and limp. Mr. Brown wants to sack Lee who he considers to be slapdash and careless, but Mrs. Brown argues that sometimes the chips are perfectly satisfactory so it can't be anything to do with Lee. She also points out that when Lee is unable to work and his friend James (a much more dependable character) stands in for him, the chips are equally variable. Preliminary Experiment As evidence Label 3 specimen tubes A B and C. Add your name to all 3. Using a measuring cylinder, pour 20cm3 of water in tube A and 10cm3 in tube B. Similarly, pour 20cm3 of 17% sucrose solution in tube C and 10cm3 in tube B. Working on a white tile, cut 6 cylinders of potato tissue out of a large potato using a cork borer. Work in the same direction. Cut all 6 to exactly the same length, eg 50mm, 60mm etc. Trim the ends at 90 degrees. Place 2 cylinders into each specimen tube. Leave the potato cylinders for 24 hours. Then using forceps, remove the cylinders from the specimen tubes, dry on a paper towel and measure. Note the new lengths and also note whether the tissue is firm or flabby. Record results. I will be using this preliminary experiment as a guide line to the actual experiment. Equipment required > 10 specimen tubes - 5 for first experiment and 5 for the repeat > Measuring cylinder - 25ml3 > Salt solution - 1M > White tile or dissecting board > 1 potato - 6 cylinders of potatoes cut from it (2 potatoes just in case) ...read more.

Middle

Analysing the mass was not as accurate as it would be expected. The original masses were not all the same and this effected the end results. They were near enough , on average, weighing at around 5 grams but they all varied between 4.75g and 5.02g. the changes in mass went in a nice trend until specimen tube 4A where the decrease in mass is less than the decrease of the potato cylinder in specimen tube 3A. This change of trend also occurs in the repeated experiment in specimen tube 5B where the previous specimen tube had a greater decrease in mass of -1.08g whereas this cylinder had a decrease in mass of -0.98g. But the description of each potato cylinder does backs up the idea that the more salt concentration there is, the more floppy the potato cylinder will be. The trends from 1A+B - 5A+B is that it should go from being hard and rigid to soft and floppy. Graph A The graph shows that as the concentration of salt solution increases, the mass of the potato cylinder will decrease. The 2 experiments (the original and the repeated) are very similar in their positions on the graph. This can be shown be the 2 'Lines of best fits' for each experiment. Even though the original experiment starts at an increase mass of 0.7g and the repeated experiment starts at an increase mass of 0.45g, they both eventually decrease to at around -0.99g. The original experiment graph line shows the right trend of movement but the repeated graph line moves out of trend at the 4th point where the line increases upwards instead of staying in trend and decreasing even further. Graph B Graph B has been taken from a preliminary experiment. The trend of the experiment is done well showing the trend of the pattern decreasing at each stage. The line of best fit fits well with the graph showing a good average decrease in mass as the concentration of salt solution increases. ...read more.

Conclusion

in the specimen tube and taking them out might not of been as accurate as it should of > Could of left the potato cylinders for longer Reliability of the Evidence The reliability of the evidence used was very reliable indeed. I had gone over 2 different books and 1 internet site which all posed the same idea of how Osmosis would occur in the different concentrations of water and salt solutions. I was very happy to see that each one backed me up on every point. The evidence was very sufficient in the idea of how I got some anomalies in the results and enabled me to figure them out. Further work could be carried out to include concentrations that increased in 0.1 M rather than 0.2. This would increase the accuracy and improve the graph. Other investigations could include using different varieties of potato or different plant tissues. I predict that for the chip placed in pure water, since there will be a higher concentration of water molecules in the external solution than in the chip, the water molecules move via osmosis from the solution into the chip's cells through the semi-permeable membrane. With the increased volume of water inside the chip's cells they become hard and turgid increasing the mass and length of the cells and therefore the chip as well. With the salt solutions there will be a higher concentration of water molecules in the chips' cells than in the external salt solution. Therefore I predict that water molecules would diffuse out of the chips' cells through the semi-permeable membrane into the external salt solution, until the equilibrium is reached. This would make the cells flaccid and in the 100% salt solution the cells could be plasmolysed due to a large amount of water molecules diffusing out of the cells. The mass and length decrease will get greater as the salt solution increases because when the cell become flaccid they shrivel reducing in size. Jus Dooooooooooooooooooooooooooooozzzzit, iiiiiiiiiiiiiiiiiiiiiiiinnnnnnnnniiiiiiiiiiittttttt,Bobby Hu...Diiiiiiced(finga in ear) ...read more.

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