A cylinder fitted with a frictionless piston contains of a monatomic ideal gas at

PHYSICS · Multi-part · A Level · Physics · Further mechanics and thermal physics · Further mechanics and thermal physics

Problem

A cylinder fitted with a frictionless piston contains

2\,\text{mol}

of a monatomic ideal gas at

300\,\text{K}

. The gas expands, doing

1500\,\text{J}

of work, and its temperature falls to

250\,\text{K}

. (Take the molar heat capacity at constant volume for a monatomic gas as

C_V=\frac{3}{2}R

.) (a) Find the change in internal energy

\Delta U

of the gas. (b) Determine the heat

Q

exchanged between the gas and the surroundings during the expansion. (c) From the sign and magnitude of

Q

, classify the process as adiabatic or non-adiabatic. State your reasoning clearly.