"One of the first rules of chemistry - always make sure liquid is in the vessel before turning on the heat source." ~ My Dad
Here is the practical lab showing why you don't want to test that lesson.
Kids, do not try this at home.
I was making noodles to go with dinner, wondering why my water was taking so long to boil. Lift the lid and find that I had forgotten to fill the pot with said water. So it has been on the hot burner, dry, for about 10 minutes.
I take the pot off the stove and in about a half second think: Is this a good idea? Pot's metal, not glass.... all the rest of dinner is ready and I don't even have the water in the pot yet....at least turn the water on Hot instead of Cold.....
I hold the very hot pot under the running water and EXPLODE instantly boiling water out the top. Then there's a strange hissing noise in the sink, and find I have blown the layered bottom completely OFF the pan! By some miracle, and with the help of our large, deep sink, I wasn't splashed a bit. My dad said that was a good example of a very violent expansion and contraction.
Enough chemistry for the day I think!