16.3 The Effect of Temperature on Spontaneity Entropy changes in the surroundings are primarily determined by heat flow Exothermic process increases the entropy in the surroundings Significance of exothermicity as a driving force depends on the temperature at which the process occurs The impact of the transfer of a given quantity of energy as heat to or fro the surroundings will be greater at lower temperatures. Characteristics of Ssurroundings The sign of Ssurr depends on the direction of the heat flow. The magnitude of Ssurr depends on the temperature.

Driving force provided by the energy flow (heat) Magnitude of the entropy change of the surroundings Quantity of heat (J) Temperature (K) = =

Quantity of heat (J) Temperature (K) Exothermic process Ssurr = + Quantity of heat (J) Temperature (K) Endothermic process Ssurr = – H T Ssurr =

Yes if Ssys > Ssurr Yes if Ssurr > Ssys Suniv Spontaneity + Yes – No ? Yes if Ssys > Ssurr Yes if Ssurr > Ssys