1. Entropy = S
Entropy is
disorder
or randomness

2. 2nd Law of Thermodynamics
Suniverse
> 0
for spontaneous processes
spontaneous =
no external intervention
Ssystem
Ssurroundings
positional disorder
energetic disorder

3. Energetic Disorder P.E. K.E. random ordered a) endothermic reaction
b) 
random
ordered
reactants
a) endothermic reaction
b) exothermic reaction
P.E.
Hsystem 0
<
products
Hsurroundings 0
>
Ssurroundings > 0

4. Ssurr depends on T Ssurr = - Hsystem (J/K) T heat  surroundings
high T
small effect
low T
relatively larger effect

5. Positional Disorder With 1 mole of gas, Not probable (1/2) (1/2) (1/2)
= 1/64
With 1 mole of gas,
Not probable

6. Positional Disorder Boltzman ordered states low probability low S
RIP
S = k ln W
W = degrees of freedom
Boltzman
ordered states
low probability
low S
disordered states
high probability
high S
 Ssystem  Positional disorder
Increases with number
of possible positions
(energy states)
Ssolids
< Sliquids
<< Sgases

7. Entropy (J/K) [heat entering system at given T] convert q to S
Pext = 1.5 atm
E = 0
w = -182 J
q = +182 J
T = 298 K
E = 0
System 2
Pext = 0 atm
w = 0
q = 0

8.  Pext = Pint + dP System 3 reversible process - infinitely slow wr=
P1 = 6.0 atm P2 = 1.5 atm
V1 = 0.4 L V2 = 1.6 L
T1 = 298 K = T2
Pext =
Pint
+ dP
reversible process
- infinitely slow V2
wr=
- Pext  dV
=- nRT dV V  =
- nRT
ln (V2/V1) V1

9. Ssystem Ssurr = - Hsystem Ssystem = qr = 1120 J T T 298 K System 1
Pext = 1.5 atm
w = -182 J
q = +182 J
S =
System 2
Pext = 0 atm
w = 0
q = 0
S =
System 3
Pext = Pint + dP
wr =
qr =
S =
-nRT ln (V2/V1)
= J J
3.77 J/K
3.77 J/K
3.77 J/K
Ssurr = - Hsystem T
Ssystem = qr T
= 1120 J
298 K

10. 3rd Law of Thermodynamics
Entropy
of a perfect crystalline
substance
at 0 K
= 0

11. Entropy curve S Temperature (K) gas liquid solid vaporization qr T
fusion
Temperature (K)

12. Entropy At 0K, S = 0 Entropy is absolute S  0
for elements in standard states
S is a State Function
Sorxn =
nSoproducts
- nSoreactants
S is extensive

13. Increases in Entropy 1. Melting (fusion) Sliquid > Ssolid
2. Vaporization Sgas >> Sliquid
3. Increasing ngas in a reaction
Heating ST2 > ST1 if T2 > T1.
Dissolution Ssolution > (Ssolvent + Ssolute) ?
6. Molecular complexity number of bonds
7. Atomic complexity e-, protons and neutrons