"Heat", in classical thermodynamics, is a derived abstraction. It's defined as the sum over a bunch of classical energies distributed among particles that beha

"Heat", in classical thermodynamics, is a derived abstraction. It's defined as the sum over a bunch of classical energies distributed among particles that behave deterministically. So this is just the measurement trick: we can't measure it therefore it's behavior is "random" from our perspective. But that's a practical limit and nothing to do with "determinism" in a mathematical sense.