Question

When a gas expands adiabatically

• A. No energy is required for expansion
• B. Energy is required and it comes from the wall of the container of the gas
• C. Internal energy of the gas is used in doing work
• D. Law of conservation of energy does not hold

Answer 1

Answer: (C)

Internal energy of the gas is used in doing work

Answer 2

$\Delta Q = \Delta U + \Delta W = 0$ ⇒ $\Delta W = - \Delta U$ if $\Delta W$ is positive i.e., gas does work then $\Delta U$ should be negative meaning internal energy is used in doing work.