Which process will increase the entropy of the local surroundings?

A. The melting of a block of ice

B. Evaporation of water vapour

C. The isothermal expansion of a gas

D. The adiabatic expansion of a gas

C

There is evidence of much guessing in this question and it elicited a few adverse comments from the teachers. But both A and B are logically equivalent so must be wrong. As an adiabatic expansion involves no thermal exchange with the surroundings, this will not affect the entropy of the local surroundings. Hence C must be correct by elimination.