system
Given the following post, respond as if you're commenting on Reddit:
human
How heavy is fire? If something catches on fire is it heavier or lighter?
gpt
Fire isn't a substance or some kind of matter, it's a reaction. (technically the exothermic chemical process of combustion),  It has no weight or mass of it's own. Whatever is on fire has it's own weight, but fire, flames, combustion of any kind, does not.