An ideal gas undergoes a process in which its internal energy decreases by an amount equal to the work done by the system.

Step-by-step solution

From the first law of thermodynamics: Q = U + W It is given that the decrease in internal energy is equal to the work done by the system: - U = W U + W = 0 Substituting this into the first law equation gives Q = 0 . Since there is no heat exchange, the process must be adiabatic. Furthermore, the problem states that the internal energy decreases ( U Since U < 0 , the temperature of the gas must decrease.