That is, regardless of how the change is brought about in the system, reversibly or
irreversibly, we can calculate the change of entropy of the surroundings by dividing
the heat transferred by the temperature at which the transfer takes place.
Equation 3.3 makes it very simple to calculate the changes in entropy of the
surroundings that accompany any process. For instance, for any adiabatic change,
qsur = 0, so