When a volume of air is compressed, which statement is correct according to ideal gas behavior used in this context?

• A. Heat is gained.
• B. Heat is lost.
• C. No heat is lost or gained.
• D. Heat is produced.

Answer: (C)

When an ideal gas is compressed in a context where no heat can flow to or from the surroundings, the process is adiabatic. The work done on the gas increases its internal energy, which raises the temperature, but there is no heat transfer across the boundary. So heat is not gained or lost. This relies on the ideal gas assumption and the adiabatic boundary condition, which is the scenario used here. If heat could flow in or out, the final temperature would differ, but under this model the heat transfer term is zero.