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)
Responses

The solution in the beaker will turn blue-black.
The solution in the beaker will turn blue-black.

The mass of the dialysis bag will increase.
The mass of the dialysis bag will increase.

The mass of the dialysis bag will decrease.
The mass of the dialysis bag will decrease.

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

The concentration of starch in the dialysis bag will increase.

Answer 1

In the investigation described, you have a dialysis bag containing a 2% iodine solution surrounded by a 9% starch solution, where the dialysis bag is permeable to water and iodine but not to starch.

Based on this setup, here are the observations that most accurately predict what will occur:

1. The solution in the beaker will turn blue-black.

   • This is because iodine from the dialysis bag will diffuse into the beaker, where it will come into contact with the starch. The starch will then react with the iodine, turning the solution in the beaker blue-black.

2. The mass of the dialysis bag will increase.

   • Water will move into the dialysis bag through osmosis, as the concentration of solutes (starch) is higher in the beaker than in the bag. This will increase the mass of the dialysis bag.

Thus, the two observations that most accurately predict what will occur are:

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