No!!! DO THAT!!! Referring to the chem guy above!
Seriously, the chemistry department chair is the nicest guy in the world, and if you get to know him, he'll be your best bud for life. (aka when you want to move into undergrad research he'll hook you up, and when you want to invite 3 extra people to the Celtics game that the ACS group goes to every year, you won't have an issue...)
But seriously, if you get to tour a department, do it. It's not like you're uber special or anything-- some departments just don't do tours, etc. Going to visit in and seeing the rooms you'll be spending half your class time in is really informative.