March 12th - Diffusion Lab

Today we completed a lab on diffusion.

The essential question was - How do cells move molecules in and out of their membranes?

Here is the Introduction of the lab:

In this lab you will observe the diffusion of a substance across a semi-permeable membrane. We will model cell membranes using a plastic bag and explore movement of molecules when we change the concentration of substances.  Iodine is a known indicator for starch. An indicator is a substance that changes color in the presence of the substance it indicates. 

Here is a link to the lab.

Here are some photos of the before and after.  The iodine diffused through the bag and reacted with the starch turning it purple!

Students need to complete the post-lab for homework.