Identify what heat and work represent

In thermodynamics, heat and work are modes of energy transfer between a system and surroundings.

They are not properties of the system themselves.

Path function vs point function

• A point function (or state function) depends only on the initial and final states. Examples: internal energy $U$, pressure $P$, volume $V$, temperature $T$.
• A path function depends on the path followed during the process.

Check heat and work

For a given change of state, the values of heat $Q$ and work $W$ can be different for different thermodynamic paths.

Hence, both $Q$ and $W$ are path functions.

Evaluate options

• A: Path functions $ightarrow$ Correct
• B: Point functions $ightarrow$ Incorrect
• C: Extensive thermodynamics state variables $ightarrow$ Incorrect, because heat and work are not state variables
• D: Intensive thermodynamic state variables $ightarrow$ Incorrect, because heat and work are not state variables

Final answer

Therefore, in thermodynamics, heat and work are path functions.