Molecular Workbench

One of my favorite Chemistry resources is Molecular Workbench.  This site, run by the Concord Consortium, offers online simulations for chemical concepts that can be very difficult for students to grasp with only paper and pencil.  My students are currently working on the Strong Chemical Bonds 2-day activity, although I've used their Intermolecular Forces module as well, with great success.  Both of these are a part of the SAM "Science of Atoms and Molecules" project.  Their website describes SAM as...

The Science of Atoms and Molecules project offers 24 research-based, field-tested activities for physics, chemistry, and biology. We provide these all freely to teachers and students online. Through the SAM activities' interactive models and simulations, we involve students in active learning. Teachers can register online to receive Teacher Guides for each activity and to gain access reporting functions to track student progress.

One feature I haven't investigated yet, is the ability to modify and make the simulations personalized.  It's on my to-do list for sure, as I'm sure the features are excellent, just like the rest of the site.

Even without personalization, I've found their simulations to be very useful.

http://mw2.concord.org/public/part2/bondtype/customDipoleMini.html

Today my students are using electronegativity values to determine if bonds between atoms are covalent, polar covalent, or ionic.  Most students have the idea that only two types of bonds exist when they enter my classroom, and this allows them to see the continuum of bond types, as well as discussing why these types of bonding occur.  With only a verbal description, very few of my students can grasp this concept, but this allows them to manipulate the bonds themselves, and provides a much deeper understanding.

If you haven't checked out what Molecular Workbench has to offer - you should!