A gas at constant volume is cooled. What can be concluded about the gas?

When a gas is cooled at constant volume, the kinetic energy of the gas molecules decreases. This occurs because temperature is directly related to the average kinetic energy of the molecules in a gas. As the gas cools, the energy of the individual particles decreases, leading to a reduction in their movement and, consequently, their kinetic energy.

In this scenario, the pressure of the gas would also decrease, assuming the gas follows the ideal gas law (PV=nRT), where pressure (P) is inversely related to temperature (T) when volume (V) is held constant. The volume does not change because it is specified that the gas is at constant volume, and the number of gas molecules remains constant unless there is a specific process that adds or removes molecules from the system. Thus, the correct conclusion is that the kinetic energy of the gas molecules has indeed decreased as a result of the cooling.