I've been wondering about what makes things melt versus light on fire, or why somethings burn at some temperature rather than melt(or vice versa) maybe I started off thinking of things burning or melting on a pan. I had this same line of thought to a large extent--some things will just melt at some temperature before they burn, but other things seem as if they will just burn (before?) they melt.
The question is WHY one and not the other or one before the other in a given circumstance.
I've had a few chemistry and physics classes, and maybe i'm just dense but it didn't appear obvious to me (at first, (at least))--i know fire is basically the result of a chemical reaction where molecules will transfer atoms/ electrons to get to a lower energy state, usually with O2 while melting is the physical process where the molecules in a substance essentially can move farther apart from each other... With a little more thought, I suppose it is just that at certain temperature some substances have enough energy to react with O2, while others don't, sometimes that's before their melting temperature, sometimes its after, and some things will never "burn," at least not with oxygen. . .
Also i'd note: if "something" melts after it "burnt" technically speaking, we should probably think of that "something" as something else now, as it has undergone a chemical reaction it is now a new chemical structure--the melting substance now is not the same thing that burnt--so i guess by definition, in essence we probably can't think a substance can burn and then melt (on a molecular level that is--although perhaps its possible for a more macroscopic thing with different sets of molecules composing it to have some molecules "burn" before others melt). Some things may only burn and never melt in our oxygen-rich air then, but i'm guessing without oxygen present we could get a lot more things to melt...
Feel free to burn me--inform me, what-not. I am down to learn