to study history or to study AP chem ????

Currently trying to study for Ap chem and history. Next period I have chem but I'm not sure how I'm gonna do I kinda know what I'm doing but I'm scared that there's gonna be a problem I don't know how to do. And my history teacher said he is expecting us to fail so I'm kinda more studying chemistry than history. 

This little calming sand thing on my math teachers desk is the only thing keeping me sane right now. 

I studied Ap chem till 2:30 am so hopefully that pays off but I'll let you know how that goes after next period.