Adiabatic Cooling occurs when

Adiabatic Cooling occurs when

• A. Air sinks and compresses, temperature decreases
• B. Air rises and expands, temperature decreases
• C. Temperature increases during expansion
• D. Temperature remains constant

Answer: (B)

Rising air cools because, as a parcel ascends, the surrounding pressure drops and the parcel expands. This expansion requires work, which uses up the parcel’s internal energy, causing its temperature to fall. In an adiabatic process no heat is exchanged with the environment, so the cooling is due entirely to this expansion. If the air sinks, it’s compressed, the parcel’s internal energy increases, and it warms adiabatically. Temperature would stay the same only if heat flowed in or out, which isn’t the case in adiabatic processes.

Rising air cools because, as a parcel ascends, the surrounding pressure drops and the parcel expands. This expansion requires work, which uses up the parcel’s internal energy, causing its temperature to fall. In an adiabatic process no heat is exchanged with the environment, so the cooling is due entirely to this expansion. If the air sinks, it’s compressed, the parcel’s internal energy increases, and it warms adiabatically. Temperature would stay the same only if heat flowed in or out, which isn’t the case in adiabatic processes.