I am going to have my potatoes in a cylindrical shape, and the variables I am going to measure are weight increase in % depending on the strength of the sugar solution.
In my experiment, I predict that potato cylinders placed in a sugar solution higher than 0.5m will gain more weight than those placed in a solution of less than 0.5m. I think this because the concentration on the outside of the membrane is likely to be lower (due to starch already contained in the potato) so the concentration will spread itself out evenly over the membrane, causing the lower molar solutions to be absorbed less than the higher ones.
I will set up my experiment as follows: I will cut 5 pieces of potato in a cylindrical shape and measure the weight of each individual piece in ounces. I will record the weight of each piece in a table.
I will then get five test tubes, and fill each with a different strength sugar solution. The five different strength solutions I will use are: 0.2 molars, 0.4m, 0.6m, 0.8m and 1m. I decided to use these strengths, as they have a suitable spacing over the range in which molar solutions vary, therefore they will give accurate and reliable results.
I will then place each of my potato pieces in a different sugar solution. Piece 1 in the 0.2m strength, piece 2 in the 0.4m strength, piece 3 in the 0.6m strength, piece 4 in the 0.8m strength and piece 5 in the 1m strength. I will measure the time, and leave each piece in the solution for exactly 30 minutes.
After the designated time, I will remove each piece and measure the weight increase of each potato piece.
I will repeat the experiment again, and use my most accurate set of results to analyze.
Observations
Here is my table of the weight of my potato pieces before they were placed in the sugar solution:
Here is my table of the weight of my potato pieces after they had been in the sugar solution:
I will now make a table showing the percentage increase of the weight of each potato piece after they have been in sugar solution.
From my results, I can show that potatoes placed in higher strength solutions gain more weight than those in lower strength solutions. The percentage increase of the potato placed in the 0.6m solution and 0.8m solution appear to be correct, however, the potato placed in the 1.0m solution appears to be incorrect. If my theory is correct, then the potato placed in the 1.0m solution should have gained more weight than the ones placed in 0.2, and 0.4m solution.
We have learnt that osmosis is the diffusion of water across a semi-permeable membrane whenever there is a difference of water concentration on either side of the membrane. In theory, we understand that the greater the concentration of the solution in which the potato is placed in, the more weight it will gain, and the lesser the concentration of the solution, then the potato will gain less weight.
According to this theory, my findings, and observations are almost correct, and were carried out in fair test conditions, so they are accurate and reliable. I believe piece of potato was left in the solution for exactly the same amount of time, so no potato piece was able to gain more or less weight in the time set.
If I were to do this experiment again, I would make sure that the starting weight of my potato cylinders was the same, as it would make calculating my results easier. I would also chose a different and perhaps more accurate variable to measure, such as surface area increase/decrease as this may give me more reliable results.
