In thermodynamics, heat and work are :

Heat and work are treated as path functions in thermodynamics.

$\DeltaQ = \DeltaU + \DeltaW$

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