Problem
• Examine the setup and experimental photos here: Molasses Thistle Tube Demo and answer the questions below.
The wide opening of the thistle tube is covered by a piece of dialysis tubing - this membrane is permeable to water, but not permeable to the solutes in the molasses. Compare the level of the molasses in the thistle tube at the beginning of the demonstration (time = 0 min), indicated by the white tape, to the level of the molasses after 60 minutes.
• Is the molasses hypertonic, hypotonic or isotonic to the water? Remember, you're describing the molasses, relative to the water, before osmosis occurs.
• Describe how the level of the molasses has changed between zero minutes and 60 minutes.
• Use your understanding of osmosis to explain why the level of the molasses changed.