Question

Why heat is a path function? How can we verify if a quantity is a path function?

Answer 1

Heat is a path function because when heat transfer is taking place, there is some change in temperature in system as well as in surrounding. Thus, there must be some work done by or work done on the system and work done is defined by path followed i.e Path Function.

Also we know that, the First Law of Thermodynamics says:

(For a process) dQ = dW, or dQ = dE + Dw; where dQ=Heat energy transferred, dW=work done, dE=energy loss(chnage in Kinetic Energy, Potential energy etc). thus Heat transfer follows a path and Hence a Path Function.