Biology Diffusion Lab

[Elizabeth in WA]

I am preparing to do this diffusion lab next friday and wanted to pass along a tip I have verified: Povidine Iodine, easily purchased under the brand name Betadine or as a generic in the antiseptic/first aid section of a grocery or drug store, will work as a starch indicator. I haven't tested diffusion through the baggies yet, but wanted to pass that tip along now that we have made pretty purple corn starch and water mixtures and gotten purple granules in a dish of sliced potato in water.

 

I'll check back next week and let everyone know how the full lab works out. :)

[Elizabeth in WA]

So... my boys couldn't wait, and the lab works using a watertight corner of a plastic grocery bag to hold the corn starch and water solution in a drinking glass with enough Betadine to make it pretty brown. I'm not sure how long it took, because we set it up in the sink and then for got about it for at least an hour. From my research it may take longer with the generic Betadine that Lugol's solution because the Betadine more slowly releases free iodine to diffuse through the bag than Lugol's solution would.

 

We'll repeat the lab formally with pictures for our notebooks on Friday, but I though I'd post the final proof of concept for using more easily aquired iodine solution.

[Michelle in AL]

Thank-you! We're doing this lab next Friday.