I came across ChemCollective while checking out my Twitter feed and it seems like a great resource to help students understand chemical reactions without needing the lab time. If you are covering a topic, but the experiment is inaccessible (cost, safety, time, etc.) then you can have your students log on to the website from in Safari and then complete the experiment online. Or perhaps you have a student who has a passion for the subject. Now they can come on to here and explore the vast array of resources available to them to help increase their knowledge. THe site also has tutorials, autograded problems, scenario based problems, molecular science modulars, and tons of other information. It is such a great resource that I'm guessing our chemistry teachers have already seen it. But it's worth checking out again to see their new site.
I had a teacher ask me if there was a way to hide or remove students who are no longer in your class. The answer is maybe. It depends on if they are officially dropped from your class and appearing as red in your roster and gradebook. If not, then no, you cannot remove them until they have been unenrolled from the class. If the student is showing up as red in your gradebook though, you can hide them so you don't have to worry about them. Here is a screenshot to help you do it: