Final answer:
The adiabatic rates of cooling and heating describe temperature changes in unsaturated air during expansion or compression without heat exchange. Adiabatic cooling happens as air expands and does work on its surroundings; adiabatic heating occurs as air is compressed and work is done on it, raising its temperature.
Step-by-step explanation:
The adiabatic rates of cooling and heating that apply to unsaturated air describe the changes in temperature of the air mass when it is expanding or compressing without exchange of heat with its surroundings.
During an adiabatic process, which is insulated from the environment, no heat enters or exits the system, and any work done by the system or on the system changes its internal energy, and hence its temperature.
Adiabatic cooling occurs when the air mass expands, doing work against the external environment and losing internal energy, which results in a decrease in temperature. Conversely, adiabatic heating occurs during compression, where work is done on the air mass, increasing its internal energy and temperature.
In the case of unsaturated air undergoing a quasi-static, adiabatic expansion, we can calculate the change in temperature using specific heat capacity at constant volume (Cv) and the first law of thermodynamics. The temperature drops in an adiabatic expansion due to the work done by the gas.
For adiabatic compression, the opposite happens, and the temperature of the unsaturated air increases because work is done on the gas, increasing its internal energy.