The groups of 5 rods were then placed into the 6 different glucose solutions with the tweezers; H 0, 0.1 mole glucose, 0.2 mole glucose, 0.3 mole glucose, 0.4 mole glucose, 0.5 mole glucose.
Each individual group of 5 rods were left in the different glucose solutions for approximately 2 hours.
After the 2 hours each group of 5 rods were dried and weighted accordingly to their groups.
RESULTS
This table below is to show the different weights obtained of the potato rods before and after being in the Varying concentrations of glucose.
This data from the table was then transferred onto a graph so the results could be compared.
CONCLUSION
The results from this table show a trend forming. It appears that as the concentrations of glucose solution increases, the weights of the potato pieces decreases.
Whilst the potato pieces were being dried it was noted that there was a different in the textures of the potato pieces between the different solutions.
The potato pieces which were in the H 0 and 0.1 mole glucose solutions, appeared very squashy in texture and appeared to have swelled in size.
The potato pieces in the more concentrated glucose solutions appeared to have shrunk in size. This difference in the textures correlated to the weights of the potatoes.
I therefore conclude that the volume of water present with the solutions determines the diffusion rate of osmosis between the potato pieces and solutions.
DISCUSSIONS
Both the water (solvent) and glucose (solute) molecules move randomly as a result of kinetic energy. In the solutions with NO glucose or a weak concentration, more water molecules are present with more energy to diffuse across the partially permeable membrane of the potato tissue. Osmosis is the movement of water molecules only, so the solute molecules cannot diffuse through the membrane, as they are too large.
The inside of the potato tissue will have a low concentration of water molecules to that of the solution, so the net movement of water molecules will move from a area of high concentration, (solution), to a area of low concentration, (inside the potato).
The above equalises the concentrations of water molecules on both sides of the partially permeable membrane, hence creating a weight gain in the weaker solutions and establishing equilibrium.
I believe that these results may be incorrect as the different groups of potato pieces all weighted differently. The graph shows a significant weight loss between the 0.1 mole and 0.2 mole, but the original weights differed considerably. I believe these provided inaccurate results for the experiment and a further improvement for this experiment would be to have each potato piece the same weight, thus creating a more fair experiment.
As the glucose concentrations increased there was a difference between the original and final weights, especially between 0.3, 0.4 solutions. This was possibly due to the solute molecules impeding the diffusion of the water molecules into the potato pieces, and the water molecules diffusing across into the glucose faster than in the opposite direction, hence explaining the weight loss.
The water molecules accumulated in the glucose solution until the concentrations became high enough to offset the blocking effect created by the solute molecules.
At this point, the molecules are able to diffuse in either direction.
The methods employed in this experiment could also have proved inaccurate.
Because of a difference in the weights of the potato pieces originally, it also questions the actual surface areas of the potato pieces. The diffusion of water molecules on a larger surface area will speed up the movement of water molecules across into the potato tissue. In further experiments the surface area of the potato pieces and the shape could be taken into consideration.
Others factors to be considered in further experiments are they length of time the potato pieces were left in the glucose solution, is 2 hours sufficient? As the process of diffusion of the water molecules is slow, so possibly the potato pieces should be left in the solution for a much longer period.
To determine if these results are correct and to establish a fair experiment this should be repeated and each factor mentioned above, considered.
