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To find the isotonic level of a potato.

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Introduction

Aim: Our aim is to find the isotonic level of a potato. Scientific explanation of what would happen: Osmosis is defined as the movement of water molecules from an area of high water concentration to an area of low water concentration, across a semi-permeable membrane. In a high concentration of water the amount of solute (e.g. sugar) is low. This could be called a weak or dilute solution. In a low concentration of water the amount of solute (e.g. sugar) 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 isotonic level). Isotonic is the net movement of water from an area of high water concentration to an area of low water concentration. Preliminary Work: For my preliminary work, we carried out an experiment that clearly explained to me the process of the movement of water molecules called osmosis. The diagram below will show the scientific explanation that was mentioned earlier. As you can see, the visking tube containing pure H O has decreased in mass due to its contents moving into the beaker therefore the visking tube containing 25% sugar solution has increased in size due to the contents of the beaker has transferred to the tubing. ...read more.

Middle

3: Stop the evaporation of any of the sugar solution. This is because if the sugar solution evaporates past the level of the potato, then the potato sample will have less surface area in the solution so this would make osmosis happen much slower. To stop any solution evaporating a cork lid can be placed on top of the test tube. 4: Accurate amount of sugar solution: More Bathing solution may affect the rate of solution. To make the amount of solution placed in the test tube as accurate as possible a syringe will be used to measure out the exact amount needed. 5: Contamination: As each test tube is filled up with the different sugar solutions the syringe which would measure the amount of solution placed in the test tube may become contaminated with different substances. To stop his from happening, the beaker and syringe must be washed every time they are used. 6: Average: To make the experiment as accurate as possible an average will be taken out of the 3 sets of results taken. We made up 3 test tubes of the same sugar solution, which is how we obtained 3 sets of results for an average. 7:Temperature: The temperature may affect the reliability of the experiment for example at extreme temperatures the cells of the potato may die and at less extreme temperatures the experiment may be speeded up. ...read more.

Conclusion

0.59 + 0.60 + 0.59 = 1.78 ? 3 = 0.593 After looking at my preliminary work it suggested that there was enough concentrations of sugar to compare each result to each other (the experiment could have been repeated with more concentrated solutions but this is not necessary). The timing of the potatoes weren't left for enough time in the experiment, as the results didn't have much change, therefore it would be much more accurate to leave them for an hour instead of half an hour to give a greater mass change. I will also be measuring the mass change as a percentage as it will be more appropriate so that reasonable results could be obtained. The graph below shows the possible outcome of the experiment. Conclusion: I feel that the experiment worked well in terms that it proved my hypothesis to be correct and we achieved what we set out to complete. I wrote my hypothesis out of my scientific knowledge for what would happen, the potato didn't taste very sweet so in this I knew the sugar content would be at a low rate. We found the isotonic value of a potato as accurately as possible by collecting an accurate set of results and finding the average. I also feel that I carried out the experiment with as much precaution / safety and fairness as possible. 0.05 0.04 0.03 0.02 0.01 0 -0.01 -0.02 -0.03 -0.04 -0.05 -0.06 -0.07 -0.08 -0.09 -0.1 -0.11 ?? ?? ?? ?? ...read more.

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Here's what a teacher thought of this essay

3 star(s)

This is a good attempt at a report, although some sections are very brief.
1. The background knowledge section is well written but lacks researched detail.
2. The fair testing section is the strongest section in the report.
3. The results are presented well.
4. The conclusion is very brief and does not fulfill the requirement of an analysis.
*** (3 stars)

Marked by teacher Luke Smithen 08/05/2013

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