Changing phase uses the latent heat of vaporization and latent heat of fusion.
Its been a very long time since I have had to remember the definitons of these so here is a Wiki link to get you started. I dont want to tell you the wrong thing.
http://en.wikipedia.org/wiki/Latent_heat
I will keep my sarcasm in check.I really do need to get a book and read.





Bookmarks