Unformatted text preview: ease in number
of molecules because any of these
changes will increase the possible
positions and energies of molecules in
the system. W = N !/ Π N i !
The Second law of thermodynamics
“A system and its surroundings spontaneously tend
towards increasing disorder”
“Natural direction of the universe tends toward
S universe = S system + S surrounding ∆Suniverse = ∆S system + ∆S surrounding ≥ 0 The entropy of the universe: increases in a spontaneous
process and remains unchanged in an equilibrium process.
(Irreversible) ∆Suniv = ∆Ssys + ∆Ssurr > 0 Equilibrium process:
(Reversible) ∆Suniv = ∆Ssys + ∆Ssurr = 0 Third
Third law of Thermodynamics
The entropy of a pure/ perfect crystalline substance
at absolute zero is zero.
zero 0 K , S Pure Crystalline = 0 S = k ⋅ ln W S = k ⋅ ln1 = 0
• Pure Crystalline
T = 0 K: Lowest possible
entropy state atoms / molecules in orderly Thermal
Thermal energy = 0
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