Osmosis on Potato Cylinders

Problem

We are going to investigate the effect of varying the concentration of sucrose solution, and using deionised water on the amount of osmotic activity between the solution and a potato chip of a given size. In this investigation the pressure and temperature in each case has to be kept the same. We also know that the volume, size and surface area of each cylinder has to be kept the same. So the only variable is the concentration of sucrose solution.

Prediction

Osmosis is defined as ‘The movement of water molecules across a partially permeable membrane from a region of high water concentration to a region of low concentration.’

Osmosis occurs across a semi-permeable membrane whenever there is a difference between the water concentrations on the two sides of the membrane and when his happens to cells they will either become turgid (if water flows into them or plasmolysed (if water flows out of them).

So I predict that when a cell is placed in high concentrated water, the water will move across the semi-permeable membrane in to the cell where there is lower concentrated water, buy osmosis and making the cell swell. This cell is now turgid. Because we are using potato cells the cells would increase in length, volume and mass because of extra water. If these potato cells were placed in a solution with a low water concentration then the opposite would happen.

I predict that the greater the concentrations of water in the external solution the greater the amount of water that enters the potato cells by osmosis. The smaller the concentration of water in the outside solution the greater the amount of water leaves the cells by osmosis.

However, there will be a point where the concentrations of water inside and outside the potato cells are equal. At this point there will be no change in the length, volume and mass of the potato, as the net movement of the water will be zero, no osmosis occurred.

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