Explanation on Osmosis and diffusion:

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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:

Using all the evidence in the preliminary work, I predict that when distilled water is surrounding the potato after a period of time, the potato will become turgid, and therefore become, stiffened, hard and enlarged, as the water concentration in the beaker would be much higher than the water in the potato.

I also predict that as more molars of sucrose solution after a certain point is used, the potato will become more flaccid, and therefore become more soft, floppy, and smaller, as the water concentration in the potato would be higher than the water concentration in the beaker.

I think this will happen because the lower the concentration of water in the sucrose solution there is, the higher the water concentration in the potato, and the more comparatively higher pressure there is in the potato, the faster osmosis would take place. This would give me a smaller potato after a set period of time, compared to a weaker solution, which would be slower, and make the potato less small over the same period.

As a result, I will be bound to find a point on my conclusive graph whereby the potato's water potential and the sucrose solution's water potential will match, and the potato, in theory, will not change size.

Theory:

In this experiment we will look at the rate of osmosis on pieces of potato. When plant cells are submersed in a solution of sucrose, the process of osmosis occurs. There are three things which could happen to the cell and it all depends on the concentration of the water in the solution.

In this diagram, the plant may become plasmolysed. This is when the concentration of water inside the cell is greater than the concentration of water outside the cell. This diffusion gradient causes water inside the plant to move out and into the sugar solution. It can move out because the plant's cell membrane is permeable to water, and will continue to do so until the concentration of water inside and outside the cells are the same. The plant loses some of the water, The cells lose their turgor, and while the cell wall still remains around the cell, it becomes very weak, or in other words plasmolysed.

In this diagram the plant may not be affected at all. This is when the concentration of water inside and outside of the plant is equal. There is no diffusion gradient and so the plant neither loses nor gains any water.
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Finally in this diagram, the plant may become turgid. This is when the concentration of water is greater outside the plant than inside it. The diffusion gradient causes water to enter the plant, causing it to expand, which results in a gain of mass.

All three of these concepts were tested in class by observing a union cell under a microscope. It is the last theory, that I have based the first part of my hypothesis on. If I leave the potato for a long time, there is more time for osmosis to take place, the ...

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