I just downloaded, installed and played with Molecular Workbench. It is simulation and modeling software that students and teachers can use to understand what happens in various chemical phenomena. I could see using this on the computer and showing it on the LCD projector to students. At the middle school level you can use to to show phase changes, diffusion, atomic structure, chemical bonds and chemical reactions. Below are 4 demonstrations that I have recorded using Jing.

Molecular motion: gas

Molecular motion: liquid

Molecular motion: solid

Molecular motion: crystalline solid to a gas

About the Author

Darren Fix is currently a middle school science teacher and part time teaching consultant. He has an M.A. in education technology and is passionate about the use of technology in the science classroom.