Diffusion an Osmosis Day 2

To begin the class, we started with a white-board session on graphs reflecting the data from the previous class. Our white board is as follows:



We then moved onto the Diffusion and Osmosis Lab.

Lab

1. First, Sid, James, and I created a cell with the dialysis tubing from a solution that was 15% Glucose and 5% Starch.
2. Then, we tested the cell to ensure that there was glucose and water to ensure that there wasn't, with a glucose strip. Then, we stuck the cell in a cup of water.
3. We added iodine into the cup to ensure that nothing leaked out of the cell, because if the cell leaked, then a reaction would occur with the iodine.
4. We let the cell sit for 15 min, then we tested the solution in a tube with 1ml of  heated Benedict's. The Benedict's is used to react with reducing sugar, i.e. the glucose in the solution, thus explaining why we tested the solution with Benedict's.
5. While we were waiting for the cell, we then cut up three slices of phenol and filled three different cups with NaOH.
6. We measured the three slices and calculated the surface area and volume of each.
7. We stuck the cubes of phenol into the NaOH and immediately they turned pink.
8. We then let them sit for a few minutes.
9. We took the cubes out and measured the volume.
10. We took out the cell we created and found it to have turned blue from the reaction.

Conclusion

The glucose and starch molecules were unable to pass through the cell membrane of the bag because they were too large. The molecules of the water and iodine, however, were small enough to diffuse through the semi-permeable membrane and thus caused the reaction.

The volume of the cubes decreased because some of the phenol molecules transferred into the NaOH to reach equilibrium.



The cell sitting in the iodine-diluted water.


The cell after the reaction.