1. Which substance(s) are entering the bag and leaving the bag? What experimental evidence supports your answer?
a. In the lab we found that glucose left the dialysis tube and entered the beaker. The glucose diffused out of the bag because the bag was hypertonic relative to it's surroundings. Since the solute concentration in the bag was greater than the environment, the solute (glucose) will diffuse out until a net movement from bag to beaker, and vise versa, of 0 is achieved. We used a test strip into the water to test for the presence of glucose. The test strip changed color, indicating that there was glucose in the beaker.
2. Explain the results you obtained. Include the concentration differences and membrane pore size in your discussion.
a. The results showed that the glucose moved out of the dialysis tubing and into the beaker. The glucose diffused across the dialysis tubing membrane and into the solution. We tested this with the test strip, which changed color, indicating the presence of glucose outside of the bag. In terms of membrane pore size, the glucose was able to diffuse across the membrane due to its small size, relative to the starch which could not.
3. Quantitative data uses numbers to measure observed changes. How could this experiment be modified so that quantitative data could be collected to show that water diffused into the dialysis bag?
a. We could have used quantitative data in the experiment by measuring the water potential and solute potential of the solutions. In doing so, we would have a more precise measure of what and how many molecules diffused across across the membrane.
4. Based on your observations, rank the following by relative size, beginning with the smallest: glucose molecules, water molecules, IKI molecules, membrane pores, starch molecules.
a. Based on our observations, the relative size of the molecules from smallest to largest is as follows: water molecules, glucose molecules, IKI molecules, membrane pores (logically placed, they were large enough to let water/glucose/IKI in but not the others), and starch, which was too large to diffuse across the membrane.
5. What results would you expect if the experiment started with a glucose and IKI solution inside the bag only starch and water outside? Why?
Had the experiment started with a glucose and IKI solution inside the bag with only starch and water outside, the glucose and IKI solution would still have diffused across the membrane and into the beaker solution of water and starch, as the concentration of glucose and IKI is lower outside the bag than inside. Starch would not move across the membrane, however, as it is too large.

1. Explain the relationship between the change in mass and the morality of sucrose within the dialysis bags.
a. The change in mass is effected by molarity of the sucrose solution. As molarity increases, so does mass. The increase in molarity means a higher concentration of sucrose, so as molarity increases, the solution becomes more hypertonic. As it becomes more hypertonic, sucrose leaves and water enters until an equilibrium is reached.
2. Predict what would happen to the mass of each bag in this experiment if all the bags were placed in a 0.4M sucrose solution instead of distilled water. Explain your response.
a. Each bag would experience different changes if they were placed in a 0.4M sucrose solution instead of water. The bag with the distilled water would decrease in mass, as water would move out of the bag via osmosis. The same will happen with the 0.2M sucrose solution in the bag, but to a lesser extent as it is closer to equilibrium than the distilled water. The 0.4M bag will experience a net movement of 0, as it is already an isotonic solution. The 0.6M, 0.8M, and 1M bags, an increase in mass will be noticed as they have a higher concentration of solute, and thus will take in water, than the solution that they are in
3. Why did you calculate the percent change in mass rather than simply using the change in mass?
a. The percent change in mass is a better measure of how much the mass changes rather than simply comparing the mass before and after. Using percent change also allows for easier comparison across multiple experiments (i.e. comparing class data).
4. A dialysis bag is filled with distilled water and then placed in a sucrose solution. The bag’s initial mass 20 g and its final mass 18 g. calculate the percent change of mass, showing your calculations here
a. Percent change in mass: 18/20=90/100. -10% change in mass.
5. The sucrose solution in the beaker would have been hypertonic to the distilled water in the bag.