An Investigation Into the Factors Affecting Osmosis

An Investigation Into the Factors Affecting Osmosis

Problem.

In this investigation I am trying to find the effect of placing

potatoes cut into French fries into salt solutions of different

concentrations and the subsequent percentage difference in weight

between potatoes placed in different salt concentrations.

Hypothesis.

Osmosis is the transfer of water from a region of high water

concentration through a selectively-permeable membrane to a region of

low water concentration. A selectively-permeable membrane will let

through small molecules such as oxygen, water and glucose but will not

allow larger molecules such as starch or protein. This can be seen in

the diagram below:

If a selectively-permeable membrane, such as a potatoes membrane,

separates a solution of high water concentration(a hypotonic solution)

from a solution of low water concentration(a hypertonic solution), the

water will move in both directions at one time. However, more water

will leave the solution of high water concentration than leaves the

solution of low water concentration. When there is the same

concentration gradient in both solutions, the system will be in

equilibrium and no water will be exchanged although the water will

continue to move around.

I think that, when placed into a solution of high salt concentration,

the potatoes cut into the shape of French fries will decrease in

weight. I predict that the higher the salt concentration, the more the

potato will decrease in weight. I believe this because the potatoes

have selectively-permeable membranes and when the concentration

gradient is higher in the potato than in the solution, the water will

pass through into the solution, and visa versa.

References.

http://www.bbc.co.uk/schools/gcsebitesize/biology/processes/diffusionandosmosisrev3.shtml

Safety.

Safety is important in every experiment. In my experiment I will be

using a sharp knife to cut the potato so I will take care when

handling that. I will keep the test tubes in a test tube rack in order

to make sure they do not smash.

Apparatus.

· Six test tubes

· Test tube rack