Potato Osmosis. Aim: To establish the effect of osmosis on the volume of a potato cylinder.

After weighting the potato discs, place these discs into a test tube and pour the required solution into it. Label the test tube with the name of the solution. Repeat the same steps above six times, each time with a different concentration of the sucrose solution (0.1 , 0.2 , 0.3 , 0.4 , 0.5). Cover the top of each test tube with a stopper and place the test tubes in the test tube rack. After 24 hours, remove the test tube and get rid of any surplus fluid inside them, then place the potato discs into in a filter paper and weight them using the same method used earlier. Record the new weights and draw a table comparing the initial and final weights of potato with each solution.

Results: _                                                                                                        

Discussion: _                                                                                              The reason for dividing each cylinder into six discs is to increase the surface area and hence the rate of osmosis in the surface of the cylinder. It was necessary to standardize the procedure of drying the discs to be as accurate as possible as the excess water on the surface of the discs is not due to osmosis and so should not be weighted. In a plant cell, the amount of water entering the cell will be limited when it reaches a certain point; this is because of the fact that the cell wall will hold the cell in shape when it is either turgid or flaccid. Having done this experiment, I now know that the solution in the vacuole of the potato has less water potential the dilute water, its concentration is equivalent to almost 0.35 mol dm-3 sucrose solution, as shown by the graph.

Evaluation:                                                                                          To make this experiment as fair as possible, I:

1. Made sure the all the experiments were made at room temperature.
2. Placed all the potatoes in their solutions for the same amount of time.
3. Covered each test tube to decrease the rate of evaporation which might increase the concentration of the sucrose solutions.
4. Cut cylinders of the same potato.

                                                                                                                  But there were certain factors that I might have made the experiment less accurate, there are:

1. The filter paper that was weighted with the potato discs might have gained weight from the water in the surface of the discs.