system
Given the following post, respond as if you're commenting on Reddit:
human
Eli5. What is a flame? I know energy is released and heat but what is a flame?
gpt
A flame is the light released by flammable gases reacting with oxygen. When you burn something, the first thing that happens is the heat causes large carbon-based molecules, like the cellulose in wood, to break down into smaller molecules, molecules small enough to be gaseous at those temperatures. These rise, because they're hotter than the air, forming that iconic flame shape as they do so. Then, because these are both hot and flammable, they react with oxygen in the air, which causes the release of light and even more heat.