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Osmosis Coursework

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Osmosis Coursework Explanation on Osmosis and diffusion: "Osmosis is the passage of water from a region of high water concentration through a semi-permeable membrane to a region of low water concentration, which will then become equal." Diffusion, although at first may seem insignificant in nature, plays quite a major part. The most obvious example would be in cells, plant and animal alike. They have partially permeable membrane in order to let in things like water, and to prevent unwanted big chemicals such as sucrose from entering. However, diffusion only takes places where there is a diffusion gradient i.e. a high concentration in one place and low in the other, moving down the diffusion gradient. Sometimes there are things which have to work against diffusion e.g. plants who need to absorb mineral ions from the soil, even though the concentration of ions is much higher in the plant that in the soil. The process of absorbing these minerals is called Active Transport. Hypothesis: I think that, as the concentration increases so will the mass of the potato. This is due to osmosis. I believe that because there will be a higher water concentration in the solution than in the potato then water will enter the potato to make the concentrations both inside and outside the potato equal. Theory: In this experiment we will look at the rate of osmosis on pieces of potato. ...read more.


Doing this preliminary work helped me make my hypothesis. It gave me a clear understanding of the process and therefore can give man idea of the rate of osmosis in a certain amount of time and different sucrose concentrations. Variables ? Mass of potatoes ~ the mass is very important because the bigger and heavier the potato chip, the longer it will take osmosis to occur. If the size of the potato chip varies, so will the amount of mass it loses or gains. The potato chip will be measured before it is put in solution, and after it has been taken out. This will let me see how much osmosis has taken place. ? Concentration of sucrose solution ~ the stronger the solution, the quicker osmosis occurs. More osmosis will occur out of the chip. Because I am investigating different sucrose concentrations, I am going to put the potato chips in different concentrations. These concentrations will be: 0.2m, 0.4m, 0.6m, 0.8m, and 1m. ? Time ~ the longer you have the potato chips in solution, the better, because more osmosis can occur. If you take the chips out after a few minutes, nothing is likely to have happened. This is why the time is important. More or less solution gets absorbed depending on the time. ? Room temperature ~ the colder it is, the longer it will take osmosis to occur. ...read more.


Table Of Results 1.0(sucrose concentration) Average % Change Mass Before 3.01,2.98,3.01 3 -27.7 Mass After 2.21,2.13,2.17 2.17 0.8(sucrose concentration) Average % Change Mass Before 2.99,2.93,2.97 2.96 -19.93 Mass After 2.31,2.39,2.40 2.37 0.6(sucrose concentration) Average % Change Mass Before 3.01, 3.05, 3.04 3.03 -15.73 Mass After 2.52, 2.55, 2.57 2.55 0.4(sucrose concentration) Average % Change Mass Before 3.04, 3.02, 3.10 3.05 -5.57 Mass After 2.86, 2.88, 2.90 2.88 0.2(sucrose concentration) Average % Change Mass Before 3.04, 2.92, 2.97 2.97 3.43 Mass After 3.10, 3.07, 3.04 3.01 As I expected. There was a greater percentage mass change as the concentration increased. This shows my prediction was correct. Conclusion I have found from my repeated results, that my prediction was correct. As the sucrose concentration rose the potato lost weight. Alternatively, as the water concentration increased the potato gained weight. This shows that osmosis happened. For example in the case of 100% sucrose solution: 1. There was more sucrose (low water concentration) outside the potato than in it. There was more water in the potato (high water concentration). 2. Water left the potato and passed through the semi-permeable potato cell membranes. 3. The levels of water concentration were then equal both inside and outside the potato 4. The weight of the potato decreased when water left it. For example, when we had an increasing concentration of water, the low water concentration solution diffused into the potato, this balanced the water concentrations inside and outside the potato. ...read more.

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Here's what a teacher thought of this essay

3 star(s)

This is a good report that has a clear structure and uses research to guide the process.
1. The introduction and background knowledge sections are well researched but this information needs to be referenced and rewritten.
2. The variables section contains a good level of detail.
3. The preliminary work is a good lead in to the investigation.
4. The results table needs to be readdressed.
5. The conclusion shows a good understanding but lacks structure and evidence.
6. There is no evaluation.
*** (3 stars)

Marked by teacher Luke Smithen 29/05/2013

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