In thermodynamics, heat and work are :

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 'U depends just on initial and final states, so 'Q i.e. heat, also has to depend on process is path