The truth is: Hmmm... I don't like chemic.
"I don't like chemic." - Just to clear out: I can say a lot of bad things about chemic instead of "I don't like". :)
I have studied it in elementary and in secondary school. Chemic was my nightmare.
Today I'm wanted to find some useful(free&linux) application about it,to my friend. After a quick search of the openSuse repositories somewhere in "Education" finally I found: Kalzium.

This program rocks. I'm browsed these molecular somethings for 30 minutes. I'm solved some functions (randomly of course), built some models, explored boiling/freezing point, etc. You can make even a 3D Rendering of molecular model. :0

If you have some experience in chemic you must to try it! It's amazing.

You can read more/download Kalzium from KDE - Education portal. http://edu.kde.org/kalzium/
BTW visit the Education portal, maybe you can find something useful about other sciences.