Wave function of a flame or fire

Yeah, what this guy said. I mean, technically each particle has a wave function and there's some horrendous mess of them, but any actual calculations you do would be much better done using Statistical Mechanics and Thermodynamics.

 

No, technically, most particles don't have a wavefunction. A wavefunction (in position space), when it exists at all (not always true in relativistic cases), is the spatial projection of a pure state (a ket). A ket can only describe a closed system, or one whose environment is wholly classical and perfectly well known. That's a useful approximation in many cases, but not in general. For a general case, the quantum states are described by density operators.