Question

Consider an adiabatic process in which a gas is compressed. Which of the following statements is strictly CORRECT regarding the energy transfer?

• A. The internal energy of the system remains constant because Q = 0.
• B. Heat is converted into work during the compression.
• C. Work is a mode of energy transfer that is stored as "Work Energy" in the system.
• D. Work is done on the system, increasing the internal energy, but the system contains no "Heat" or "Work."

Hint:

Always remember:
Internal Energy ($U$) is a State Function (stored in the system).
Heat ($Q$) and Work ($W$) are Path Functions (energy in transition across boundaries).

Answer 1

The Correct Option is D

Step 1: Understanding the Question:
The question tests key conceptual definitions in thermodynamics regarding path functions (heat, work) and state functions (internal energy) during an adiabatic compression.

Step 2: Key Formula or Approach:
According to the First Law of Thermodynamics:
\[ dU = dQ - dW \]
For an adiabatic process, there is no heat transfer across the boundary:
\[ dQ = 0 \implies dU = -dW \]

Step 3: Detailed Explanation:

• Heat ($Q$) and Work ($W$) are defined strictly as energy in transit across a boundary. They are path functions, meaning they only exist during a process.

• A thermodynamic system does not possess or contain "heat" or "work". It only possesses internal energy ($U$), which is a state function.

• During an adiabatic compression, work is done on the system ($dW < 0$), which causes the internal energy to increase ($dU > 0$).

• The work done is converted into internal energy (microscopic kinetic and potential energy of the gas molecules), not stored as some separate "work energy" category.

• Therefore, statement (D) is the only conceptually accurate statement.

Step 4: Final Answer:
Work is done on the system, increasing the internal energy, but the system contains no "Heat" or "Work."