Diffusion Lab

I did this lab last year without lab sheets and had students record observations in their journals. I've put the lab sheets together. As usual, I may add to it next year - for example, I'd like to add a section on calculating the rate of diffusion, but I haven't had the time or energy to put it in yet. I may also play around with putting some starch into the mix and using starch indicator instead of food coloring. Still, the basic set-up will be the same.

I've seen other labs out there that use gelatin cubes placed in food coloring or other substances and incorporate surface area:volume ratios. For now I'm keeping it simple. I use a petri dish with gelatin and add food coloring to a well in the center, then measure the distance it diffuses over a 5 day period.

An added bonus, if you wait long enough, is the growth of mold on the surface, which is a whole other science lesson in itself on extra-cellular digestion and enzymes. I generally do this lab after the detergent enzymes with jello lab, so I try to get students to make the connection before I have to point it out to them. Anyway, here it is.

Diffusion Through Gelatin