Is it possible to tell me how to figure out how much fire weighs? It cannot be a gas, for it is fire, and fire is fueled by gasses. It cannot be heavy, because fire seems to float upwards, (hot air rises). But at the same time it cannot be lighter than air, because of the simple fact that it stays fixed to the material it is consuming. (example: fire stays on logs burning in fireplace) Fire contradicts itself. A Physics Professor told me once that the question, "what does fire weigh?" is something only taught to physics majors that are in their second semester of their senior year. He never gave me a straight answer. Can you help me figure out how much fire weighs? Thank you for your time.