Explanation:
The behavior of an ideal gas during expansion is described by the gas law, which relates the pressure (P), volume (V), temperature (T), and number of molecules (n) of the gas. The gas law can be expressed mathematically as PV = nRT, where R is the gas constant.

When an ideal gas expands, its volume increases, and the pressure decreases. The temperature of the gas may increase or decrease depending on the conditions of the expansion. There are three possible scenarios:

1. Adiabatic expansion: In an adiabatic expansion, the gas expands without exchanging heat with its surroundings. This means that there is no heat transfer between the gas and the environment, and the internal energy of the gas remains constant. In this case, the temperature of the gas decreases as it expands because the internal energy is converted into work.

2. Isothermal expansion: In an isothermal expansion, the gas expands while maintaining a constant temperature. This means that the gas is in thermal equilibrium with its surroundings, and heat is transferred in and out of the gas to maintain the temperature. In this case, the temperature of the gas remains constant as it expands because the heat transfer balances the work done by the gas.

3. Non-adiabatic and non-isothermal expansion: In this case, the gas expands while exchanging heat with its surroundings, but the temperature may increase or decrease depending on the conditions of the expansion. If the gas absorbs more heat than it loses during the expansion, its temperature will increase. If the gas loses more heat than it absorbs, its temperature will decrease.

Therefore, the correct answer to the question "When an ideal gas expands, its temperature" is option D, "may increase or decrease," because the temperature of the gas depends on the conditions of the expansion, such as whether it is adiabatic, isothermal, or non-adiabatic and non-isothermal.