teacher’s domain http://www.teachersdomain.org/sci/index.html is a wonderful resource for teaching (and learning). You should register, but if you’re just checking it out you can ‘take a test-drive’. Alternatively you can simply click on the test-drive option if you want to call up a video-clip without having to sign in.

Not all of the resources are videos, and as always check them out yourself in advance before showing them to the troops.

I have linked to many of the useful physics ones on my site, but if I had to pick one clip it would probably be this one. At 1:15 it’s just what you need to reinforce a very strange idea indeed!

http://www.teachersdomain.org/resources/phy03/sci/phys/matter/atoms/index.html