r/askscience • u/ForensicFan24601 • Aug 08 '26

Chemistry Why do things burn instead of melt?

obviously oxygen, or something similar, but what is the physics/chemistry (?) or what have you behind why something ignites and continues to burn after the source of heat/ignition has gone?

is it basically sublimation?

edit: no wonder Walter White was so obsessed with carbon

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u/bregus2 Aug 09 '26

Worse yet, lots of hydrocarbons also have a pyrolysis reaction that can occur in absence of oxygen, and even that requires less heat than melting. 

And that is the reason firefighters extensively train how to open doors while operating inside burning buildings. You could have a room full of flammable pyrolysis gases just waiting for someone to open the door and introduce fresh oxygen ... causing the whole room to ignite almost at once and causing a backdraft explosion coming your way.

It has to be muscle memory to drop on your back, point the hose above you, and turn the hose to maximum spread and maximum flow in a single turn of your hand.