system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What are we smelling when it smells 'hot' or 'cold'?

For example, if a hair straightener is left on, you can smell it, but it smells 'hot', not like anything specific. Or sometimes if you go outside, it smells cold.
gpt
You're not smelling the heat, your smelling the heat's effects on the environment. That hair straightener singed some hairs and lofted some lovely burnt flesh scent into the air, you smell it and immediately know that there is a hot element around somewhere because your brain has made that association many times before.