Someone asked for an intuitive picture of how a system could attain a
temperature greater than that of the heat source that triggers the
heating. This result can occur if the initial state of the system is
not an equilibrium state in the sense that it is not in its lowest
free energy state. A supercooled liquid might behave in this manner,
for example. Nonequilibrium systems (in this sense) are not that
uncommon. You can find such systems quite frequently on the third
finger, left hand, of engaged ladies.