What osmosis is?

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OSMOSIS COURSEWORK

What osmosis is?

Osmosis is the net movement of a solvent through a semi permeable membrane (as of a living cell) into a solution of higher solute concentration that tends to equalize the concentrations of solute on the two sides of the membrane

        

This means that…

If you were to put cell into liquid containing water one of three things will happen.

  • If the medium surrounding the cell has a higher water concentration than the cell (a very dilute solution) the cell will gain water by osmosis.
    Water molecules are free to pass across the cell membrane in both directions, but more water will come into the cell than will leave. The net (overall) result is that water enters the cell. The cell is likely to swell up.
  • If the medium is exactly the same water concentration as the cell there will be no net movement of water across the cell membrane.
    Water crosses the cell membrane in both directions, but the amount going in is the same as the amount going out, so there is no overall movement of water. The cell will stay the same size.
  • If the medium has a lower concentration of water than the cell (a very concentrated solution) the cell will lose water by osmosis.
    Again, water crosses the cell membrane in both directions, but this time more water leaves the cell than enters it. Therefore the cell will shrink.

Aim

To find out whether osmosis affects potato cells in different concentrations of water, if so how if affects them.

Hypothesis

 I predict that if the concentration of the solution is greater than that of the potato then the length of the potato chip will decrease. My reasoning behind this is that if the concentration of glucose is higher in the solution, then the water will leave the potato to dilute the solution and leave the potato with less water and a reduced length. The water will flow across the semi-permeable membrane from the potato to the solution to try to even out the potential gradient.

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  However, if a potato chip is placed into a solution of 0 molar concentrations, it should gain length. This is because the solution has more water potential (its molecules’ ability to move) than the potato chip, and so water moves from a region of high concentration (the solution) to a region of low concentration (the potato chip.)

 

Method

 

  1. Using a cork borer cut slices of potato about 4 centimetres long. You can later cut them down to size if they’re too big or too small.
  2. Cut them down so that the length of the potato ...

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