Question

Which from following thermodynamic properties is a path function?

• A. Internal energy
• B. Work
• C. Entropy
• D. Enthalpy

Hint:

Remember that Work ($W$) and Heat ($Q$) are path functions, while Internal Energy ($U$), Enthalpy ($H$), Entropy ($S$), and Gibbs Free Energy ($G$) are state functions. Changes in state functions are independent of the path.

Answer 1

The Correct Option is A

Step 1: Define path functions and state functions in thermodynamics.

• State functions (or point functions) are properties that depend only on the state of the system (initial and final states) and not on the path taken to reach that state. Their change is an exact differential (e.g., $\text{d}U, \text{d}S, \text{d}H$).
• Path functions are properties that depend on the specific path or sequence of steps taken during a process from an initial state to a final state. Their change is an inexact differential (e.g., $\delta W, \delta Q$).

Step 2: Analyze each given option based on the definitions.

• Internal energy (A): Internal energy ($\Delta U$) is a state function. Its change depends only on the initial and final states of the system.
• Work (B): Work ($W$) is a path function. The amount of work done by or on a system depends on the specific process path (e.g., reversible vs. irreversible, constant volume vs. constant pressure) taken between two states.
• Entropy (C): Entropy ($\Delta S$) is a state function. Its change depends only on the initial and final states of the system.
• Enthalpy (D): Enthalpy ($\Delta H$) is a state function. Its change depends only on the initial and final states of the system.

Step 3: Conclude which property is a path function. Based on the analysis, Work is the only path function among the given options.