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My Aim in this piece of Coursework is to discover which factors can influence the rate of osmosis in a potato.

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The Aim: My Aim in this piece of Coursework is to discover which factors can influence the rate of osmosis in a potato. Introduction: In this course work I have been asked to find out what factors affect the process of Osmosis. The Dictionary explains Osmosis as, "Diffusion of fluid through a semi permeable membrane from a solution with a low solute concentration to a solution with a higher solute concentration until there is an equal concentration of fluid on both sides of the membrane". Water diffuses from where it is a high concentration to where it is a low concentration along a concentration gradient; it does this because the membrane tries to even up the amount of water on each side of itself. The effect of all this is to gradually dilute the sugar solution. However, the cell will reach a point where its vacuole may fill up with too much water, and cannot take in any more water it is 'fully turgid'. The vacuole in the cell can also be deprived from water and cannot shrink anymore the cell is then flaccid. Diagram A Diagram A shows Plasmolysis occurring when a plant cells membrane shrinks away from its cell wall. This occurs when water is drawn out of the cell and into the outside fluid. (Water diffuses from where it is a high concentration to where it is a low concentration). Preliminary work: For my preliminary work, I used 24mm of potato. It was easy to cut 24mm. ...read more.


to a region of low concentration (the potato chip.) Fair Test: Except for the variables everything else that could be changed must be kept the same like length of potato, size of borer etc. Apparatus: Knife, White Tile, Borer, 6 plastic cups, Ruler, 0%, 2%, 4%, 6%, 8%, 10% Sugar solutions Method: 1. I took an average sized ground potato and checked that it was both healthy and hard. 2. Using a borer I carved 18 pieces out of the potato and cut each one into an even block approximately 24mm on a white tile. 3. Using a scalpel and ruler I cut the potato into chips that were 24mm long. I had to be very careful whilst cutting the potato, as the scalpel is exceptionally sharp. I then had 18 chips. 4. Taking 6 plastic cups I lined them up and labeled them 0%, 2%, 4%, 6%, 8%, and 10%. 5. Using a measuring cylinder I measured out 15mls of each sugar solution, which I then poured into the corresponding plastic cups. 6. I swiftly put 3 potato chips into each cup and then left them for 24 hours. 3 chips were used to create an average, which would give me a better set of results and more accurate graphs. 8. After 24 hours I set out some paper towels with which I was going to dry up the solution once I was done and I drew up a basic table for my results. 9. ...read more.


This would explain why potato chips put into a solution of 0 molar seemed very firm compared to the potato chip used for 1 molar, this was because the cells of the potato had lost their turgor, and had become flaccid. Evaluation: When it came to accuracy during this experiment, it was extremely difficult to maintain. For example, we had to, for as much as possible, keep each potato chip the same surface area. However, putting this theory into practice wasn't easy. Even if you cut three potato chips, each measuring 24mm, it was very unlikely that they would all be the same length and width. This inaccuracy was due to human error, it is very difficult to make 18 potato chips exactly the same. In future, I would make a template, or use a cutter to make all my potato chips the same. Another inaccuracy was when we put the potato chips into the solutions, because it was impossible to not leave a small interval between each test tube. The first test would have been going for a few seconds longer than the last. In future I will time each individual potato chip and leave 1-minute intervals, which then will give me time to immerse all 18 pieces. Therefore it will then give me time to remove each potato chip after 24 hours making it a fairer test. I could extend this Coursework by investigating osmosis with a different factor as opposed to concentration of water. I could investigate the effects of temperature, surface area or weight on Osmosis. This would give me a very clear understanding and knowledge of osmosis in potatoes. Daniel Swabey 11SG Page 1 09/05/2007 Mr Benford 11a2 ...read more.

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