james bond
Well-Known Member
OK, in an environment under constant pressure and temperature(like our atmosphere), the appropriate variable to deal with both heat flow and entropy is called the Gibb's fre energy and is G=H-ST. Here, H is the heat, S is the entropy, and T is the temperature. A reaction is spontaneous only if G decreases. This can happen in two main ways: H decreases (heat flows out of the system) or S increases (entropy increases).
So, for example, when water freezes, S decreases, but H also decreases (heat flows out of the water). If the temperature T is low enough the change in H compensates for the change in S and the water will freeze. But if T is large, the entropy part dominates and the water does not freeze, it melts.
Okay, but where are you going with this?