A gas confined by a frictionless piston is maintained at a constant external pressure of 100kPa. The gas expands from an initial volume of 0.40L to a final volume of 1.20L. During the expansion the internal energy of the gas increases by 120J.
(a) Calculate the work done on the gas during the expansion. Express your answer with the appropriate sign and in joules.
(b) Determine the amount of thermal energy transferred during the process and state clearly whether the gas is heated or cooled.