1. When an ideal gas is expanded adiabatically in volume at constant pressure, the average kinetic energy of the gas molecule: A. Increase B. decreases C. Does no change

i know the answer is B but can someone explain why please? i thought it does not change since its adiabatically.

The 1st law of thermodynamics

ΔQ=ΔU+W= ΔU+pΔV
For adiabatic process ΔQ=0 =>
0=ΔU+pΔV
if p=const and ΔV ↑ => ΔU ↓
The internal energy ΔU depends on temperature; and temperature decreases as the kinetic energy of particles decreases