Can I login the same account but in different expansions at the same time?

As the title says, is that possible? Currently i'm on a 1300 queue on Icecrown and just wanna check my account and play on Frostwolf (mists) while waiting.

Can I login to Mists while i'm on Icecrown queue? I'm afraid to try it right now because I might lose my queue position on Icecrown. Thanks in advance to those who could help!

Yes, you can use your account on multiple realms at the same time. It won't disconnect you unless you try to connect to the same realm.