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Investigate Osmosis In Potato Chips.

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Introduction

Title: Investigate osmosis in potato chips. Aim: To see how different concentrations of saltwater affects osmosis on potato chips To find the isotonic solution for potato cells To find the water potential of potato cells. Method: Cut 18 cylinders of potato of 50mm each Dry cylinders Weigh cylinders and record weight Prepare saltwater solutions at set concentrations Pipette 30mm3 of each solution into separate Petri dishes Leave for 3 hours Remove and dry cylinders Weigh cylinders and record weight. Apparatus: 200mm3 1 molar saltwater solution 200mm3 Distilled water Electronic balance Graduated pipette Knife Large potato No. 4 cork borer 6 Petri dishes with lids. Rule Stop watch Test tube holder 6 Test tubes Tissue How it will be kept fair (independent and fixed variables): ? Potato will be cut into cylinders using a no. 4 cork borer. They will be cut to 50mm each, so it has a close to the same surface area as possible. ? The same potato will be use as there may be differences between potatoes. ? The cylinders will be weighed on the same electronic balance at its most accurate degree which is 10 mg. ? ...read more.

Middle

? There will be lids on the Petri dishes so no water can evaporate, because this would change the concentration of the solutions. ? 3 potato cylinders will be placed in each solution so I can have a good average, and if one result is anomalous I will still have two other results to go on. They will be placed in the exact same solution so I can be sure they undergo the same conditions. Each lid will be labelled with which cylinder it is above so I don't use the wrong initial weight to work out its percentage change from the original. ? All of the Petri dishes will be exposed to the same light, temperature and pressure, as they will be left in the same area of a room. Although these variables will not be constant they will be the same, e.g. if a light is switched off they will all have no light. ? All the Petri dishes will be left for 3 hours before they are weighed. This should give ample time for a real difference to be seen without the potato cylinder pulverizing or decomposing. ...read more.

Conclusion

I will put the averages on a simple table like this: Solution Chip no. Initial weight Final weight Percentage change Average percentage Moles mg mg % change % 0 1 2 I shall put my results on a graph, with solution on the horizontal axis and percentage changed from the original on the vertical. I will plot the average percentage for each solution and mark the 100% line. Where the graph line hits the 100% line the solution will be isotonic for this type of potato and I can see the water potential of the potato cells. These are the water potentials for each solution: Table 3 Solution Water potential 0m 0 0.2m 1.5184 MPa 0.4m 1.0368 MPa 0.6m 2.592 MPa 0.8m 3.456 MPa 1.0m 4.32 MPa At the point where the concentration of the solution is equal to that of the potato cell I can find out the water potential of the potato cells by multiplying the concentration by 4.32 MPa. I can check if this is right by ensuring the answer is between 0 and 1.5185 MPa. Water potential = concentration x 4.32 MPa Planning Bekki Le Prevost Science Mock Coursework 4/11/01 Page 2 Planning Bekki Le Prevost Science Mock Coursework 4/11/01 ...read more.

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