Investigation on Osmosis.

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Carly Mckenzie

        19TH April 2002

 

Investigation on Osmosis

Aim

We are trying to discover how changing a certain variable would affect the rate of osmosis of skinless potatoes.

Variables

There are several factors which affect the rate of osmosis such as the potato (in this case) must not have any peel on it as the peel of a potato is impermeable and therefore would prevent the movement of the water. Here are the possible variables (listed below): -

  • The width and length give different surface areas which change the amount of osmosis performed by the plant (bigger surface area = more osmosis and vice versa)

  • Different vegetables have different concentrations of solution inside

  • Temperature-high temperatures give a faster rate of osmosis

  • The volume of the solution-the potato must be entirely covered for complete osmosis

  • Light intensity-strong light gives heat. (Heat as said above)

  • The type of solution e.g. sugar solution

  • Must use the same potato as different potatoes may have different concentrations inside

  • Must have a bung to prevent evaporation of the solution

We are changing the concentration of the solution. We are going to be changing it to 0.0M, 0.2M, 0.4M, 0.6M and 0.8M.

 

Prediction

Osmosis is the movement of water from a dilute solution (lots of H20) to a concentrated solution (little H20) through a semi-permeable membrane. The experiment we are performing determines how different concentrations of solutes (e.g. salt) affect the rate of osmosis.

Below shows a diagram of osmosis

From the pilot experiment we could see that when the potatoes were placed a dilute solution (where there is more water and less solute) water from outside of the potato would move in to balance the concentration both inside and out, causing the potato to gain weight. We could also see that when the potato was placed in a more concentrated solution (where there is less water and more solute) water from inside the potato will move out to equal the concentration both in and outside, causing the potato to lose weight.

From the results that we gathered from out pilot experiment we can estimate that the concentration inside of our potato is 0.34M (approximately). We know this because when the potato was placed in a solution less than 0.34M, it gained weight and when it was placed in a solution with a concentration higher than 0.34M it lost weight.

From this we can predict that if we place out potato chips in a solution less than 0.34M such as 0.0M or 0.2M our chips will gain weight (through the process of osmosis). The potato will gain the most weight when placed in solution 0.0M as there is more water inside than out causing water to move in. If we place them in a solution more than 0.34M such as 0.4M, 0.6M or 0.8M they will all lose weight (through the process of osmosis). The potato will lose the most weight when placed in a solution of 0.8M as there is less water outside than inside thus the water moves out causing the potato to lose weight.

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The chips placed in a solution 0.4M will lose weight but only a fractional amount compared to the amount of weight lost by the potato chips placed in 0.6M or 0.8M. This is because the difference in concentration inside and outside of the potato has a difference of 0.06M and so the potato doesn’t lose too much water thusly the potato doesn’t lose too much weight. When the potato is placed in a solution of 0.4 molar I think that the potato’s weight will stay around the same as the difference in concentration between the outside and inside of ...

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