Heat is Path Function

Lets us consider following two cycles: 1a2b1 and la2cl

Figure 6.2

(6.3)

or,

(6.4)

Subtracting Eq. (6.4) from Eq. (6.3)

(6.5)

Since, work depends on the path

(6.6)

(6.7)

Energy transfer as heat is not a point function, neither is it a property of the system.

Heat interaction is a path function.