In thermodynamics, heat and work are :

(1)

Heat and work are treated as path functions in thermodynamics.

$\Delta \mathrm{Q}=\Delta \mathrm{U}+\Delta \mathrm{W}$

Since work done by gas depends on type of process i.e. path and $\Delta U$ depends just on initial and final states, so $\Delta Q$ i.e. heat, also has to depend on process is path.