S = k log W (we will never actually use this formula)
S = an energy that is a measure of the disorder in a system
Ssolid < Sliquid < Ssolution <<< Sgas
Three Laws of Thermodynamics:
1. Energy is conserved
2. The entropy of a closed system always increases
3. The entropy of a perfect crystal at 0K is 0
For a reaction, we look at ΔS--the change in entropy from reactants to products:ΔS = Sproducts - Sreactants
(using coefficients, just like using ΔHf.)
The signs are opposite here: more disorder (positive ΔS) is favorable, while less (negative) is unfavorable.
Often, the sign of ΔS can be determined simply by looking at the compounds--making or using up gas is most important, but things like precipitation are predictable as well.
Because entropy depends on temperature, the units are an energy (J/mol) per Kelvin: J/mol*K