Biology Biology 2.1 Making 2.1 Making

ChipsChipsBy: Biology 12BBy: Biology 12B

The experiment that we carried out was to find out how different salt solutions affect osmosis in potato pieces.

The independent variable was the concentration of salt. There was a total of six different solutions as follows: 0.1, 0.3, 0.5, 0.7, 0.9 mol L-1 and distilled water.

The Dependent Variable was the amount of water lost or absorbed by the potato due to osmosis and diffusion. This would be measured by weighing the potato chip before and after the experiment to find the difference.

To ensure the reliability of the data, it needed to be a fair test. Each trial was carried out with three pieces of potato. This was collectively eighteen chips of potato, or three per vial.

All other variables that could affect the data had to be controlled, or kept the same. For example surface area of each potato piece, and the set of electric scales used.

When the results had been recorded I found that they proved my hypothesis correct. The distilled water pieces had gained weight, or absorbed water, and the other solution potato chips had lost weight (or water).

The results showed that osmosis has occurred in the distilled water vial, because the concentration of water particles outside the potato was higher than inside the potato. This lead to osmosis until the vial contents reached an equilibrium of water concentration.

In the salt solution vials, there was a higher concentration of water particles inside the potato than outside. The water there fore moved through the semi permeable membrane and attempted to reach an equilibrium between the potato and salt solution.

The water moved to dilute the salt so that either side of the semi permeable membrane had the same concentration of salt.

Touching of chips may have affected results or reduced the surface area available for osmosis and diffusion (therefore reducing the rate of particle movement).One thing that I think could have influenced the results is having three pieces of potato in the one vial. It was quite cramped and I think that possibly it restricted surface area when sides were touching over large areas. As surface area is so influential on the rate of osmosis and diffusion this could have seriously altered the results.

To improve the experiment I think that each potato piece should be isolated rather than in a vial with others.

On the graph there were some large changes in weight gain and loss between solutions, and to make sure that this is not incorrect I would recommend ‘in between’ solutions are tested. For example not just 0.1 to 0.3, but also testing a 0.2 solution.

By Carragh. K.