Prince Rupert's drop

Check out the video of this unique glass formation with strange physical properties filmed in slow motion and explained better than anyone else does.



So, physics connections here:

1. Notice the glass as it breaks -- what direction does it travel? Why does it travel this way? What is the average velocity of all the particles when the glass breaks in the air (not on the anvil)?
2. Think about thermodynamics. Why do these different bonds form inside?
3. Think about forces. Can you explain the balanced forces before breaking and unbalanced forces after? Can you explain the how we see force pairs in this demonstration?