Dialysis bags can be used as models of cells to explore the movement of materials into and out of cells. Students set up an investigation with a dialysis bag containing a 2% iodine solution in a beaker containing a 9% starch solution as shown in the figure. Starch turns blue-black in the presence of iodine. The dialysis bag is permeable to water and iodine but not to starch.

Question

Which two observations most accurately predict what will occur in the investigation?
(4 points)
• The solution in the dialysis bag will turn blue-black.
• The solution in the beaker will turn blue-black.
• The mass of the dialysis bag will decrease.
• The mass of the dialysis bag will increase.
• The concentration of starch in the dialysis bag will increase.

Answer 1

In the given scenario with the dialysis bag containing a 2% iodine solution placed in a beaker with a 9% starch solution, we can make predictions based on the properties of the substances involved and the permeability of the dialysis bag.

1. Observation: The solution in the dialysis bag will turn blue-black.

   • This observation is accurate because iodine (which is in the dialysis bag) is able to diffuse out of the bag and into the beaker. Since the bag is permeable to iodine, it will come in contact with starch (in the beaker), and a blue-black color will develop as the iodine interacts with starch.

2. Observation: The mass of the dialysis bag will increase.

   • This is also an accurate prediction because water will move into the dialysis bag via osmosis. Since the concentration of starch is higher in the beaker (9%) than inside the dialysis bag (where the starch concentration is 0%), water will move into the bag to balance the concentrations, causing the mass of the dialysis bag to increase.

Therefore, the two correct observations are:

• The solution in the dialysis bag will turn blue-black.
• The mass of the dialysis bag will increase.