IB Chemistry on Entropy and Laws of Thermodynamics

1. E = sum kinetic energy/motion of molecule, and potential
energy represented by chemical bond bet atom
∆E = q + w
∆E = Change internal
energy
q = heat
transfer
w = work done
by/on system
Thermodynamics
Study of work, heat and energy on a system
∆E universe = ∆E sys + ∆E surrounding = 0
1st Law Thermodynamics
Entropy - Measure of disorder
↓
∆S uni = ∆S sys + ∆S surr > 0 (irreversible rxn)
↓
All spontaneous rxn produce increase in entropy of universe
2nd Law Thermodynamics
∆S uni = ∆S sys + ∆S surr
Isolated system - Entropy change of universe always increase
Click here thermodynamics entropy
Entropy
Measure molecular disorder/randomness
↓
More disorder - More dispersion of matter/energy
↓
More random - Rxn toward right- Entropy Increases ↑
Direction to right- Spontaneous to right →
2nd Law
Thermodynamics
Embrace the chaos
Over time - Entropy increase ↑
Direction to left ← Never happen !
Click here thermodynamics
Energy cannot be created or destroyed
> 0

2. ∆S = Entropy
change
Entropy
Dispersal/DistributionMatter Energy
Matter more disperse ↑
Entropy increases ↑
solid liquid gas
spontaneous - entropy ↑
Over time - Entropy increase ↑
Phase change - sol → liq → gas
↓
Entropy increase ↑
Every energy transfer - increase entropy universe
Entropy universe can only go up - never go down
Entropy increase - many ways energy spread out
Dispersion energy as heat - increase entropy
Stoichiometry- more gas/liq in product
↓
Entropy increase ↑
T
Q
S 
Heat added ↑
Phase change Stoichiometry
Embrace the chaos
N2O4(g) → 2NO2(g)
1 2
2H2O(l) → 2H2 (g) + O2 (g)
1 2
3
3
More gas in product - Entropy ↑
Heat added ↑
Entropy
Measure molecular disorder/randomness
↓
More disorder - More dispersion of matter/energy
↓
More randon - Rxn towards right- Entropy Increases ↑
Liq more disorder than solid
Gas more disorder than liq
kinetic energy distributed
over wide range
Q = heat
transfer
T = Temp/K
Distribution matter in space Distribution energy bet particles
Direction to left ← Never happen !Direction to right- Spontaneous to right →

3. Statistical
Entropy
Entropy
Measure molecular disorder/randomness
↓
More disorder - More dispersion of matter/energy
↓
More random - Entropy Increases ↑
1st Law Thermodynamics - Doesn't help explain direction of rxn
∆S uni> 0 (+ve) → More disorder - spontaneous
∆S uni < 0 (-ve) → More order - non spontaneous
Change sol → liq → gas - Higher entropy
Greater number particles in product - Higher entropy
More complex molecule - More atoms bonded - Higher entropy
Higher temp - Vibrate faster - More random - Higher entropy
Why gas mixes and not unmix? Why heat flow from hot to cold?
Entropy
Notes on Entropy
1st Law Thermodynamics 2nd Law Thermodynamics
Energy cannot be created or destroyed
Transfer from one form to another
∆E universe = ∆E sys + ∆E surrounding = 0
Isolated system
↓
∆S uni always increase
∆E = q + w
Method to calculate entropy
Number microstates
Thermodynamic
Entropy
Heat + Temp involved
Gas mixesSolution diffuse Heat flow hot →cold
X X X
∆E = internal
energy
q = heat
transfer
w = work done ∆S = Entropy
universe
∆S = Entropy
system
∆S = Entropy
surrounding
∆S uni = ∆S sys + ∆S surr
Law Thermodynamics
1 2
∆S = Entropy
uni
WkS ln
∆S = Entropy
change
k = boltzmann
constant
W = Microstate
Click here statistical entropy Click here thermodynamics entropy
Why solution diffuse and not undiffuse?
Unit - J mol -1 K-1
surrsysuni SSS 
∆S = Entropy
sys and surr

4. 1st Law Thermodynamics - Doesn't help explain direction of rxn
∆S uni> 0 (+ve) → More disorder - spontaneous
∆S uni < 0 (-ve) → More order - non spontaneous
Change sol → liq → gas - Higher entropy
Greater number particles in product - Higher entropy
More complex molecule - More atoms bonded - Higher entropy
Higher temp - Vibrate faster - More random - Higher entropy
Measure molecular disorder/randomness
↓
More disorder - More dispersion of matter/energy
↓
More random - Entropy Increases ↑
Isolated system
↓
∆S uni always increase
Entropy
Why gas mixes and not unmix? Why heat flow from hot to cold?
Notes on Entropy
1st Law Thermodynamics 2nd Law Thermodynamics
Energy cannot be created or destroyed
Transfer from one form to another
∆E universe = ∆E sys + ∆E surrounding = 0
∆E = q + w
Gas mixesSolution diffuse Heat flow hot →cold
X X X
∆E = internal
energy
q = heat
transfer
w = work done ∆S = Entropy
universe
∆S = Entropy
system
∆S = Entropy
surrounding
∆S uni = ∆S sys + ∆S surr
Law Thermodynamics
3rd Law Thermodynamics
Unit - J mol -1 K-1
Standard Molar Entropy, S0
Entropy perfectly crystal at 0K = 0
Std molar entropy, S0
↓
S0 when substance heated from 0K to 298K
Std state - 1 atm / 1M sol
Temp = 298K
Std Molar Entropy/S0 S0 at 298 /JK-1 mol-1
Fe (s) + 27
H2O (s) + 48
Na (s) + 52
H2O (l) + 69
CH3OH (l) + 127
H2 (g) + 130
H2O (g) + 188
CO2 (g) + 218
Solid - Order
↓
Entropy Lowest
Liq - Less order
↓
Entropy Higher
Gas - Disorder
↓
Entropy Highest
Entropy highest
Why solution diffuse and not undiffuse?

5. Entropy
Why gas mix and not unmix?Why solution diffuse and not undiffuse? Why heat flow from hot to cold?
Gas mixesSolution diffuse Heat flow hot →cold
X X X
Unit - J mol -1 K-1
Standard Molar Entropy, S0
Entropy perfectly crystal at 0K = 0
↓
S0 when substance heated from 0K to 298K
Std state - 1 atm / 1M sol
Temp = 298K
Std Molar Entropy/S0 S0 at 298 /JK-1 mol-1
Fe (s) + 27
H2O (s) + 48
Na (s) + 52
H2O (l) + 69
CH3OH (l) + 127
H2 (g) + 130
H2O (g) + 188
CO2 (g) + 218
Solid - Order
↓
Entropy Lowest
Liq - Less order
↓
Entropy Higher
Gas - Disorder
↓
Entropy Highest
Entropy
highest
Entropy
Standard Molar Entropy, S0
Depend on
Temp increase ↑ - Entropy increase ↑
Physical/phase state
Dissolving solid Molecular mass
Click here thermodynamics entropy Ba(OH)2
Temp
Temp/K 273 295 298
S0 for H2 + 31 + 32 + 33.2
Sol → Liq → Gas - Entropy increase ↑
State solid liquid gas
S0 for H2O + 48 + 69 + 188
entropy increase ↑ entropy increase ↑
Depend on
Substance NaCI NH4NO3
S0 for solid + 72 + 151
S0 for aq + 115 + 260
More motion - entropy increase ↑ Higher mass - entropy increase ↑
Substance HF HCI HBr
Molar mass 20 36 81
S0 + 173 + 186 + 198
S0 = 0 at 0K
All sub > 0K, have +ve S0

6. Entropy perfectly crystal at 0K = 0
↓
S0 when substance heated from 0K to 298K
Entropy
Why gas mix and not unmix?Why solution diffuse and not undiffuse? Why heat flow from hot to cold?
Gas mixesSolution diffuse Heat flow hot →cold
X X X
Unit - J mol -1 K-1
Standard Molar Entropy, S0
Std state - 1 atm / 1M sol
Temp = 298K
Std Molar Entropy/S0 S0 at 298 /JK-1 mol-1
H2O (s) + 48
Na (s) + 52
H2O (l) + 69
CH3OH (l) + 127
H2O (g) + 188
CO2 (g) + 218
Solid - Order
↓
Entropy Lowest
Liq - Less order
↓
Entropy Higher
Gas - Disorder
↓
Entropy Highest
Entropy
highest
Entropy
Standard Molar Entropy, S0
Depend on
Temp increase ↑ - Entropy increase ↑
Physical/phase state
Dissolving solid Molecular mass
Temp
Temp/K 273 295 298
S0 for H2 + 31 + 32 + 33.2
Sol → Liq → Gas - Entropy increase ↑
State solid liquid gas
S0 for H2O + 48 + 69 + 188
entropy increase ↑ entropy increase ↑
Depend on
More motion - entropy increase ↑
Click here entropy
notes
Click here entropy,
enthalpy free energy data
Click here entropy
CRC data booklet
Higher mass - entropy increase ↑
S0 = 0 at 0K
All sub > 0K, have +ve S0
Substance NaCI NH4NO3
S0 for solid + 72 + 151
S0 for aq + 115 + 260
Substance HF HCI HBr
Molar mass 20 36 81
S0 + 173 + 186 + 198

7. Entropy
Why gas mixes and not unmix?Why conc solution diffuse and not undiffuse? Why heat flow from hot to cold?
Entropy
Thermodynamic Entropy
Gas mixesSolution diffuse Heat flow hot →cold
X X X
1
Quatitatively
T
H
T
Q
Ssurr


Quatitatively
Entropy sys ↓ decrease - More order - Less number gas
↓
Entropy surr ↑ increase - Heat release increase ↑ motion surr particles
↓
Heat release by sys to surr increase ↑ entropy surr
↓
∆S surr > ∆S sys (More +ve)
↓
∆S uni = ∆S sys + ∆S surr
↓
∆S uni > 0 - Combustion at 298K - Spontaneous
surrsysuni SSS 
)tan()( treacprosys SSS 
C3H8(g) + 5O2 (g) → 3CO2(g) + 4H2O(l) ∆H = -2220 kJ at 298K
C3H8(g) + 5 O2 (g) → 3 CO2(g) + 4 H2O(l)
S0 +270 +205 x 5 +213 x 3 +70 x 4
1295 919
Reactant Product
1
7450
298
)2220000(






JKS
S
T
H
S
surr
surr
surr
1
)tan()(
376
1295919




JKS
S
SSS
sys
sys
treacproductsys
1
70747450376 


JKS
SSS
uni
surrsysuni
∆H = -2220 kJ
= -2220000J
surrsysuni SSS 
S /JK-1
Assume Q = H at constant pressure
+ve
-ve
spontaneous
∆Ssys = - 376
∆Ssurr = +7450
=+
∆Suni = + 7074
∆S uni > 0 (+ve) → Spontaneous
∆S uni < 0 (-ve) → Non spontaneous
Is Combustion at
298K spontaneous?

8. Entropy
Why gas mixes and not unmix?Why conc solution diffuse and not undiffuse? Why heat flow from hot to cold?
Entropy
Thermodynamic Entropy
Gas mixesSolution diffuse Heat flow hot →cold
X X X
1
Quatitatively
T
H
T
Q
Ssurr


Quatitatively
Entropy sys ↓ decrease - More order - Less number gas
↓
Entropy surr ↑ increase - Heat released increase ↑ motion surr particles
↓
Heat release by sys to surr increase ↑ entropy surr
↓
∆S surr > ∆S sys (More +ve)
↓
∆S uni = ∆S sys + ∆S surr
↓
∆S uni > 0 - Combustion at 298K - Spontaneous
surrsysuni SSS 
)tan()( treacprosys SSS 
CH4(g) + 2O2 (g) → CO2(g) + 2H2O(g) ∆H = - 890 kJ at 298K
CH4(g) + 2 O2 (g) → CO2(g) + 2 H2O(g)
S0 + 186 +205 x 2 +213 + 188 x 2
+ 596 + 589
Reactant Product
1
2986
298
)890000(






JKS
S
T
H
S
surr
surr
surr
1
)tan()(
7
596589




JKS
S
SSS
sys
sys
treacproductsys
1
297929867 


JKS
SSS
uni
surrsysuni
∆H = - 890 kJ
= - 890 000J
surrsysuni SSS 
S /JK-1
+ve
-ve
spontaneous
∆Ssys = - 7
∆Ssurr = + 2986
=+
∆Suni = + 2979
∆S uni > 0 (+ve) → Spontaneous
∆S uni < 0 (-ve) → Non spontaneous
Assume Q = H at constant pressure
Is Combustion at
298K spontaneous?

9. Entropy
Why gas mixes and not unmix?Why conc solution diffuse and not undiffuse? Why heat flow from hot to cold?
Entropy
Thermodynamic Entropy
Gas mixesSolution diffuse Heat flow hot →cold
X X X
1
Quatitatively
T
H
T
Q
Ssurr


Quatitatively
Entropy sys ↓ decrease - More order - Liquid form
↓
Entropy surr ↑ increase - Heat released increase ↑ motion surr particles
↓
Heat release by sys to surr increase ↑ entropy surr
↓
∆S surr > ∆S sys (More +ve)
↓
∆S uni = ∆S sys + ∆S surr
↓
∆S uni > 0 - Condensation at 298K - Spontaneous
surrsysuni SSS 
)tan()( treacprosys SSS 
H2O (g) → H2O(l) ∆H = - 44.1 kJ at 298K
H2O (g) → H2O(l)
S0 + 188 + 70
+ 188 + 70
Reactant Product
1
148
298
)44100(






JKS
S
T
H
S
surr
surr
surr
1
)tan()(
118
18870




JKS
S
SSS
sys
sys
treacproductsys
1
30148118 


JKS
SSS
uni
surrsysuni
∆H = -44.1 kJ
= - 44 100J
surrsysuni SSS 
S /JK-1
+ve
-ve
spontaneous
∆Ssys = - 118
∆Ssurr = + 148
=+
∆Suni = + 30
∆S uni > 0 (+ve) → Spontaneous
∆S uni < 0 (-ve) → Non spontaneous
Condensation steam at
298K (25C) spontaneous?
Assume Q = H at constant pressure

10. Entropy
Why gas mixes and not unmix?Why conc solution diffuse and not undiffuse? Why heat flow from hot to cold?
Entropy
Thermodynamic Entropy
Gas mixesSolution diffuse Heat flow hot →cold
X X X
1
Quatitatively
T
H
T
Q
Ssurr


Quatitatively
Entropy sys ↑ increase - More disorder - More gas atoms form
↓
Entropy surr ↓ decrease - Heat absorb decrease ↓ motion surr particles
↓
Heat absorb by sys from surr decrease ↓ entropy surr
↓
∆S surr < ∆S sys (More -ve)
↓
∆S uni = ∆S sys + ∆S surr
↓
∆S uni < 0 - Atomization at 298K - Non Spontaneous
surrsysuni SSS 
)tan()( treacprosys SSS 
H2(g) → 2 H(g) ∆H = + 436 kJ at 298K
H2 (g) → 2 H(g)
S0 + 130 + 115 x 2
+ 130 + 230
Reactant Product
1
1463
298
)436000(






JKS
S
T
H
S
surr
surr
surr
1
)tan()(
100
130230




JKS
S
SSS
sys
sys
treacproductsys
1
13631463100 


JKS
SSS
uni
surrsysuni
∆H = + 436 kJ
= + 436 000J
surrsysuni SSS 
S /JK-1
+ve
-ve
non - spontaneous
∆Ssys = +100
∆Ssurr = - 1463
=+
∆Suni = - 1363
∆S uni > 0 (+ve) → Spontaneous
∆S uni < 0 (-ve) → Non spontaneous
Is Atomization of H2 at
298K spontaneous?
Assume Q = H at constant pressure

11. Entropy
Why gas mixes and not unmix?Why conc solution diffuse and not undiffuse? Why heat flow from hot to cold?
Entropy
Thermodynamic Entropy
Gas mixesSolution diffuse Heat flow hot →cold
X X X
1
Quatitatively
T
H
T
Q
Ssurr


Quatitatively
Entropy sys ↓ decrease - More order - Solid form
↓
Entropy surr ↑ increase - Heat released increase ↑ motion surr particles
↓
Heat release by sys to surr increase ↑ entropy surr
↓
∆S sys > ∆S surr (More -ve)
↓
∆S uni = ∆S sys + ∆S surr
↓
∆S uni < 0 - Freezing at 298K - Non Spontaneous
surrsysuni SSS 
)tan()( treacprosys SSS 
H2O (l) → H2O(s) ∆H = - 6 kJ at 298K
H2O (l) → H2O(s)
S0 + 70 + 48
+ 70 + 48
Reactant Product
1
20
298
)6000(






JKS
S
T
H
S
surr
surr
surr
1
)tan()(
22
7048




JKS
S
SSS
sys
sys
treacproductsys
1
22022 


JKS
SSS
uni
surrsysuni
∆H = -6 kJ
= - 6000J
surrsysuni SSS 
S /JK-1
+ve
-ve non - spontaneous
∆Ssys = - 22
∆Ssurr = + 20
=+
∆Suni= - 2
∆S uni > 0 (+ve) → Spontaneous
∆S uni < 0 (-ve) → Non spontaneous
Is Freezing water to ice at
298K (25C) spontaneous?
Assume Q = H at constant pressure

12. Entropy
Why gas mixes and not unmix?Why conc solution diffuse and not undiffuse? Why heat flow from hot to cold?
Entropy
Thermodynamic Entropy
Gas mixesSolution diffuse Heat flow hot →cold
X X X
1
Quatitatively
T
H
T
Q
Ssurr


Quatitatively
Entropy sys ↓ decrease - More order - Solid form
↓
Entropy surr ↑ increase - Heat released increase ↑ motion surr particles
↓
Heat release by sys to surr increase ↑ entropy surr
↓
∆S surr > ∆S sys (More +ve)
↓
∆S uni = ∆S sys + ∆S surr
↓
∆S uni > 0 - Freezing at 263K (-10C) - Spontaneous
surrsysuni SSS 
)tan()( treacprosys SSS 
H2O (l) → H2O(s) ∆H = - 6 kJ at 263K
H2O (l) → H2O(s)
S0 + 70 + 48
+ 70 + 48
Reactant Product
1
8.22
263
)6000(






JKS
S
T
H
S
surr
surr
surr
1
)tan()(
22
7048




JKS
S
SSS
sys
sys
treacproductsys
1
8.08.2222 


JKS
SSS
uni
surrsysuni
∆H = -6 kJ
= - 6000J
surrsysuni SSS 
S /JK-1
+ve
-ve
spontaneous
∆Ssys = - 22
∆Ssurr = + 22.8
=+
∆Suni= + 0.8
∆S uni > 0 (+ve) → Spontaneous
∆S uni < 0 (-ve) → Non spontaneous
Is Freezing water to ice at
263K (-10C) spontaneous?
Assume Q = H at constant pressure

13. Entropy
Why gas mixes and not unmix?Why conc solution diffuse and not undiffuse? Why heat flow from hot to cold?
Entropy
Thermodynamic Entropy
Gas mixesSolution diffuse Heat flow hot →cold
X X X
1
Quatitatively
T
H
T
Q
Ssurr


Quatitatively
Entropy sys ↑ increase - More disorder - Gas form
↓
Entropy surr ↓ decrease - Heat absorb decrease ↓ motion surr particles
↓
Heat absorb by sys from surr decrease ↓ entropy surr
↓
∆S surr < ∆S sys (More -ve)
↓
∆S uni = ∆S sys + ∆S surr
↓
∆S uni < 0 - Decomposition at 298K - Non Spontaneous
surrsysuni SSS 
)tan()( treacprosys SSS 
CaCO3 (s) → CaO(s) + CO2(g) ∆H = + 178 kJ at 298K
CaCO3 (s) → CaO (s) + CO2(g)
S0 + 93 + 40 + 213
+ 93 + 253
Reactant Product
1
597
298
)178000(






JKS
S
T
H
S
surr
surr
surr
1
)tan()(
160
93253




JKS
S
SSS
sys
sys
treacproductsys
1
437597160 


JKS
SSS
uni
surrsysuni
∆H = + 178 kJ
=+ 178 000J
surrsysuni SSS 
S /JK-1
+ve
-ve non - spontaneous
∆Ssys = + 160
∆Ssurr = - 597
=+
∆Suni= - 437
∆S uni > 0 (+ve) → Spontaneous
∆S uni < 0 (-ve) → Non spontaneous
Decomposition CaCO3 at
298K (25C) spontaneous?
Assume Q = H at constant pressure

14. Entropy
Why gas mixes and not unmix?Why conc solution diffuse and not undiffuse? Why heat flow from hot to cold?
Entropy
Thermodynamic Entropy
Gas mixesSolution diffuse Heat flow hot →cold
X X X
1
Quatitatively
T
H
T
Q
Ssurr


Quatitatively
Entropy sys ↑ increase - More disorder - Gas form
↓
Entropy surr ↓ decrease - Heat aborb decrease ↓ motion surr particles
↓
Heat absorb by sys from surr decrease ↓ entropy surr
↓
∆S sys > ∆S surr (More +ve)
↓
∆S uni = ∆S sys + ∆S surr
↓
∆S uni > 0 - Decomposition at 1500K - Spontaneous
surrsysuni SSS 
)tan()( treacprosys SSS 
CaCO3 (s) → CaO(s) + CO2(g) ∆H = + 178 kJ at 1500K
CaCO3 (s) → CaO (s) + CO2(g)
S0 + 93 + 40 + 213
+ 93 + 253
Reactant Product
1
118
1500
)178000(






JKS
S
T
H
S
surr
surr
surr
1
)tan()(
160
93253




JKS
S
SSS
sys
sys
treacproductsys
1
42118160 


JKS
SSS
uni
surrsysuni
∆H = + 178 kJ
=+ 178 000J
surrsysuni SSS 
S /JK-1
+ve
-ve
spontaneous
∆Ssys = + 160
∆Ssurr = - 118
=+
∆Suni = + 42
∆S uni > 0 (+ve) → Spontaneous
∆S uni < 0 (-ve) → Non spontaneous
Decomposition CaCO3 at
1500K (1227C) spontaneous?
Assume Q = H at constant pressure

15. Entropy
Why gas mixes and not unmix?Why conc solution diffuse and not undiffuse? Why heat flow from hot to cold?
Entropy
Thermodynamic Entropy
Gas mixesSolution diffuse Heat flow hot →cold
X X X
1
Quatitatively
T
H
T
Q
Ssurr


Quatitatively
Entropy sys ↓ decrease - More order - Less gas form
↓
Entropy surr ↑ increase - Heat release increase ↑ motion surr particles
↓
Heat release by sys to surr increase ↑ entropy surr
↓
∆S surr > ∆S sys (More +ve)
↓
∆S uni = ∆S sys + ∆S surr
↓
∆S uni > 0 - Oxidation at 298K - Spontaneous
surrsysuni SSS 
)tan()( treacprosys SSS 
2NO(g) + O2(g) → 2NO2(g) ∆H = - 114 kJ at 298K
2 NO(g) + O2 (g) → 2NO2(g)
S0 + 210 x 2 + 102 + 240 x 2
+ 522 + 480
Reactant Product
1
382
298
)114000(






JKS
S
T
H
S
surr
surr
surr
1
)tan()(
42
522480




JKS
S
SSS
sys
sys
treacproductsys
1
33938242 


JKS
SSS
uni
surrsysuni
∆H = - 114 kJ
= - 114 000J
surrsysuni SSS 
S /JK-1
+ve
-ve
spontaneous
∆Ssys = - 42
∆Ssurr = + 382
=+
∆Suni = + 339
∆S uni > 0 (+ve) → Spontaneous
∆S uni < 0 (-ve) → Non spontaneous
Is Oxidation of NO at
298K (25C) spontaneous?
Assume Q = H at constant pressure

16. Entropy
Why gas mixes and not unmix?Why conc solution diffuse and not undiffuse? Why heat flow from hot to cold?
Entropy
Thermodynamic Entropy
Gas mixesSolution diffuse Heat flow hot →cold
X X X
1
Quatitatively
T
H
T
Q
Ssurr


Quatitatively
Entropy sys ↓ decrease - More order - Less gas form
↓
Entropy surr ↑ increase - Heat release increase ↑ motion surr particles
↓
Heat release by sys to surr increase ↑ entropy surr
↓
∆S surr > ∆S sys (More +ve)
↓
∆S uni = ∆S sys + ∆S surr
↓
∆S uni > 0 - NH3 production at 298K - Spontaneous
surrsysuni SSS 
)tan()( treacprosys SSS 
N2(g) + 3H2(g) → 2NH3(g) ∆H = - 92 kJ at 298K
N2(g) + 3H2 (g) → 2NH3(g)
S0 + 192 + 131 x 3 + 192 x 2
+ 585 + 384
Reactant Product
1
308
298
)92000(






JKS
S
T
H
S
surr
surr
surr
1
)tan()(
201
585384




JKS
S
SSS
sys
sys
treacproductsys
1
107308201 


JKS
SSS
uni
surrsysuni
∆H = - 92 kJ
= - 92 000J
surrsysuni SSS 
S /JK-1
+ve
-ve
spontaneous
∆Ssys = - 201
∆Ssurr = + 308
=+
∆Suni = + 107
∆S uni > 0 (+ve) → Spontaneous
∆S uni < 0 (-ve) → Non spontaneous
Is Haber, NH3 production
298K (25C) spontaneous?
Assume Q = H at constant pressure
NH3

17. Entropy
Why gas mixes and not unmix?Why conc solution diffuse and not undiffuse? Why heat flow from hot to cold?
Entropy
Thermodynamic Entropy
Gas mixesSolution diffuse Heat flow hot →cold
X X X
1
Quatitatively
T
H
T
Q
Ssurr


Quatitatively
Entropy sys ↓ decrease - More order
↓
Entropy surr ↑ increase - Heat release increase ↑ motion surr particles
↓
Heat release by sys to surr increase ↑ entropy surr
↓
∆S surr > ∆S sys (More +ve)
↓
∆S uni = ∆S sys + ∆S surr
↓
∆S uni > 0 - AI production at 298K - Spontaneous
surrsysuni SSS 
)tan()( treacprosys SSS 
Fe2O3(s) + 2AI(s) → 2Fe(s) + AI2O3(s) ∆H = - 851 kJ at 298K
+ 143 + 105
Reactant Product
1
2855
298
)851000(






JKS
S
T
H
S
surr
surr
surr
1
)tan()(
38
143105




JKS
S
SSS
sys
sys
treacproductsys
1
2817285538 


JKS
SSS
uni
surrsysuni
∆H = - 851 kJ
= - 851 000J
surrsysuni SSS 
S /JK-1
+ve
-ve
spontaneous
∆Ssys = - 38
∆Ssurr = + 2855
=+
∆Suni = + 2817
∆S uni > 0 (+ve) → Spontaneous
∆S uni < 0 (-ve) → Non spontaneous
Is Thermite, AI production
298K (25C) spontaneous?
Assume Q = H at constant pressure
Fe2O3(s) + 2AI(s) → 2Fe(s) + AI2O3(s)
S0 + 87 + 28 x 2 + 27 x 2 + 51

18. Entropy
Why gas mixes and not unmix?Why conc solution diffuse and not undiffuse? Why heat flow from hot to cold?
Entropy
Thermodynamic Entropy
Gas mixesSolution diffuse Heat flow hot →cold
X X X
1
Quatitatively
T
H
T
Q
Ssurr


Quatitatively
Entropy sys ↓ decrease - More order
↓
Entropy surr ↑ increase - Heat release increase motion surr particles
↓
Heat release by sys to surr increase ↑ entropy surr
↓
∆S surr > ∆S sys (More +ve)
↓
∆S uni = ∆S sys + ∆S surr
↓
∆S uni > 0 - Decomposition KCIO3 at 298K - Spontaneous
surrsysuni SSS 
)tan()( treacprosys SSS 
4KCIO3(s) → 3KCIO4(s) + KCI(s) ∆H = - 144 kJ at 298K
+ 572 + 535
Reactant Product
1
483
298
)144000(






JKS
S
T
H
S
surr
surr
surr
1
)tan()(
37
572535




JKS
S
SSS
sys
sys
treacproductsys
1
44648337 


JKS
SSS
uni
surrsysuni
∆H = - 144 kJ
= - 144 000J
surrsysuni SSS 
S /JK-1
+ve
-ve
spontaneous
∆Ssys = - 37
∆Ssurr = + 483
=+
∆Suni = + 446
∆S uni > 0 (+ve) → Spontaneous
∆S uni < 0 (-ve) → Non spontaneous
Is decomposition KCIO3
298K (25C) spontaneous?
Assume Q = H at constant pressure
∆S/∆H constant over range of temp
4KCIO3(s) → 3KCIO4(s) + KCI(s)
S0 + 143 x 4 + 151 x 3 + 82

19. Entropy
Why gas mixes and not unmix?Why conc solution diffuse and not undiffuse? Why heat flow from hot to cold?
Entropy
Thermodynamic Entropy
Gas mixesSolution diffuse Heat flow hot →cold
X X X
1
Quatitatively
T
H
T
Q
Ssurr


Quatitatively
Entropy sys ↑ increase - More disorder
↓
Entropy surr ↑ increase - Heat release increase ↑ motion particles
↓
Heat release by sys to surr increase ↑ entropy surr
↓
∆S surr + ∆S sys > 0 (More +ve)
↓
∆S uni = ∆S sys + ∆S surr
↓
∆S uni > 0 Combustion sugar at 298K - Spontaneous
surrsysuni SSS 
)tan()( treacprosys SSS 
C6H12O6(s) + 6O2 (g) → 6CO2(g) + 6H2O(l) ∆H = - 2810 kJ at 298K
+ 821 + 1698
Reactant Product
1
9430
298
)2810000(






JKS
S
T
H
S
surr
surr
surr
1
)tan()(
877
8211698




JKS
S
SSS
sys
sys
treacproductsys
1
103079430877 


JKS
SSS
uni
surrsysuni
∆H = - 2810 kJ
= - 2810 000J
surrsysuni SSS 
S /JK-1
+ve
-ve
spontaneous
∆Ssys = + 877
∆Ssurr = + 9430
=+
∆Suni = + 10307
∆S uni > 0 (+ve) → Spontaneous
∆S uni < 0 (-ve) → Non spontaneous
Is combustionsugar
298K (25C) spontaneous?
Assume Q = H at constant pressure
∆S/∆H constant over range of temp
C6H12O6 (s) + 6O2(g) → 6CO2(g) + 6H2O(l)
S0 + 209 +102 x 6 + 213 x 6 + 70 x 6

20. ∆S uni = ∆S sys + ∆S surr
↓
∆S uni > 0
∆S uni = ∆S sys + ∆S surr
↓
∆S uni > 0
q = heat
transfer
Isolated system
∆S uni always increase
1st Law Thermodynamics 2nd Law Thermodynamics
Energy cannot be created or destroyed
Transfer from one form to another
∆E universe = ∆E sys + ∆E surrounding = 0
∆E = q + w
∆E = internal
energy
w = work done ∆S = Entropy
universe
∆S = Entropy
system
∆S = Entropy
surrounding
∆S uni = ∆S sys + ∆S surr
Law Thermodynamics
3rd Law Thermodynamics
Unit - J mol -1 K-1
Standard Molar Entropy, S0
Entropy perfectly crystal at 0K = 0
Std molar entropy, S0
S0 when substance heated from 0K to 298K
Std state - 1 atm / 1M sol
Temp = 298K
spontaneous+ve
-ve
=
S /JK-1
Exothermic - Heat released
∆Ssys = + ve
∆Ssurr = + ve
∆Suni = + ve
+
∆S sys + ve , ∆S surr +ve
↓
Suni > 0
(Rxn always spontaneous)
Exothermic - Heat released
+ve
-ve
∆Ssys = - ve
+
∆Ssurr = + ve
∆Suni = + ve
= spontaneous
∆S sys - ve and ∆S surr + ve
↓
Suni > 0
(Rxn spontaneous)
Endothermic - Heat absorb
S /JK-1
S /JK-1
∆Ssys = + ve
+
∆Ssurr = - ve
=
∆Suni = + ve
∆S sys + ve and ∆S surr - ve
↓
Suni > 0
(Rxn spontaneous)
spontaneous
∆S uni = ∆S sys + ∆S surr
↓
∆S uni > 0
C6H12O6(s) + 6O2 (g) → 6CO2(g) + 6H2O(l) ∆H = - 2810 kJ
Spontaneous / non spontaneous
∆Hsys and ∆Suni
2NO(g) + O2(g) → 2NO2(g) ∆H = - 114 kJ CaCO3 (s) → CaO(s) + CO2(g) ∆H = + 178 kJ
∆H = -ve ∆H = -ve ∆H = +ve

21. ∆S uni = ∆S sys + ∆S surr
↓
∆S uni< 0
∆S uni = ∆S sys + ∆S surr
↓
∆S uni < 0
∆S uni = ∆S sys + ∆S surr
↓
∆S uni < 0
q = heat
transfer
Isolated system
∆S uni always increase
1st Law Thermodynamics 2nd Law Thermodynamics
Energy cannot be created or destroyed
Transfer from one form to another
∆E universe = ∆E sys + ∆E surrounding = 0
∆E = q + w
∆E = internal
energy
w = work done ∆S = Entropy
universe
∆S = Entropy
system
∆S = Entropy
surrounding
∆S uni = ∆S sys + ∆S surr
Law Thermodynamics
3rd Law Thermodynamics
Unit - J mol -1 K-1
Standard Molar Entropy, S0
Entropy perfectly crystal at 0K = 0
Std molar entropy, S0
S0 when substance heated from 0K to 298K
Std state - 1 atm / 1M sol
Temp = 298K
Non
spontaneous
+ve
-ve
=
S /JK-1
Endothermic - Heat absorb
∆Ssys = + ve
∆Ssurr = - ve
∆Suni = - ve
+
∆S sys + ve , ∆S surr - ve
↓
Suni < 0
(Rxn always Non spontaneous)
Exothermic - Heat released
+ve
-ve
∆Ssys = - ve
+
∆Ssurr = + ve
∆Suni = - ve
=
∆S sys - ve, ∆S surr + ve
↓
Suni < 0
(Rxn Non spontaneous)
Endothermic - Heat absorb
S /JK-1 S /JK-1
∆Ssys = + ve
+
∆Ssurr = - ve
=
∆Suni = - ve
∆S sys + ve and ∆S surr - ve
↓
Suni < 0
(Rxn Non spontaneous)
Spontaneous / non spontaneous
∆Hsys and ∆Suni
∆H = + ve ∆H = + ve ∆H = - ve
CaCO3 (s) → CaO(s) + CO2(g) ∆H = + 178 kJ H2O (l) → H2O(s) ∆H = - 6 kJ
Non
spontaneous
H2(g) → 2 H(g) ∆H = + 436 kJ
Non
spontaneous

22. Entropy
Why gas mixes and not unmix?Why conc solution diffuse and not undiffuse? Why heat flow from hot to cold?
Predict entropy change - quatitatively
Gas mixesSolution diffuse Heat flow hot →cold
X X X
Reactant Product
CH4(g) + 2O2 (g) → CO2(g) + 2H2O(l)
CH4(g) + 2 O2 (g) → CO2(g) + 2 H2O(l)
∆Hf
0 - 74 0 - 393 - 286 x 2
S0 + 186 +205 x 2 + 213 + 70 x 2
∆Hsys
θ = ∑∆Hf
θ
(pro) - ∑∆Hf
θ
(react)∆Ssys
θ = ∑Sf
θ
(pro) - ∑Sf
θ
(react)
1
)tan()(
243
596353




JKS
S
SSS
sys
sys
treacproductsys
1
2990
298
)891000(






JKS
S
T
H
S
surr
surr
surr
kJHsys 891)74(965 
surrsysuni SSS 
1
27472990243 


JKS
SSS
uni
surrsysuni
Is Combustion at
298K spontaneous?
Unit for ∆S - JK-1 Unit for ∆H -
kJ
∆S uni = ∆S sys + ∆S surr
↓
∆S uni > 0 - Combustion at 298K - Spontaneous
C3H8(g) + 5O2 (g) → 3CO2(g) + 4H2O(l)
C3H8(g) + 5 O2 (g) → 3 CO2(g) + 4 H2O(l)
∆Hf
0 - 104 0 - 393 x 3 - 286 x 4
S0 +270 +205 x 5 +213 x 3 + 70 x 4
Reactant Product
∆Ssys
θ = ∑Sf
θ
(pro) - ∑Sf
θ
(react) ∆Hsys
θ = ∑∆Hf
θ
(pro) - ∑∆Hf
θ
(react)
1
)tan()(
376
1295919




JKS
S
SSS
sys
sys
treacproductsys kJHsys 2219)104(2323 
1
7446
298
)2219000(






JKS
S
T
H
S
surr
surr
surr
surrsysuni SSS 
1
70707446376 


JKS
SSS
uni
surrsysuni
∆S uni = ∆S sys + ∆S surr
↓
∆S uni > 0 - Combustion at 298K - Spontaneous
1 2

23. Entropy
Why gas mixes and not unmix?Why conc solution diffuse and not undiffuse? Why heat flow from hot to cold?
Predict entropy change - quatitatively
Gas mixesSolution diffuse Heat flow hot →cold
X X X
Reactant Product
∆Hsys
θ = ∑∆Hf
θ
(pro) - ∑∆Hf
θ
(react)∆Ssys
θ = ∑Sf
θ
(pro) - ∑Sf
θ
(react)
1
)tan()(
118
18870




JKS
S
SSS
sys
sys
treacproductsys
1
148
298
)44000(






JKS
S
T
H
S
surr
surr
surr
kJHsys 44)242(286 
surrsysuni SSS 
1
30148118 


JKS
SSS
uni
surrsysuni
Is Condensation/Freezing at
298K spontaneous?
∆S uni = ∆S sys + ∆S surr
↓
∆S uni > 0 - Condensation at 298K - Spontaneous
Reactant Product
∆Ssys
θ = ∑Sf
θ
(pro) - ∑Sf
θ
(react) ∆Hsys
θ = ∑∆Hf
θ
(pro) - ∑∆Hf
θ
(react)
1
)tan()(
22
7048




JKS
S
SSS
sys
sys
treacproductsys kJHsys 6)286(292 
1
20
298
)6000(






JKS
S
T
H
S
surr
surr
surr
surrsysuni SSS 
1
22022 


JKS
SSS
uni
surrsysuni
∆S uni = ∆S sys + ∆S surr
↓
∆S uni < 0 -Freezing at 298K - Non Spontaneous
3 4H2O (g) → H2O(l) H2O (l) → H2O(s)
H2O (g) → H2O(l)
∆Hf
0 - 242 - 286
S0 + 188 + 70
H2O (l) → H2O(s)
∆Hf
0 - 286 - 292
S0 + 70 + 48

24. Entropy
Why gas mixes and not unmix?Why conc solution diffuse and not undiffuse? Why heat flow from hot to cold?
Predict entropy change - quatitatively
Gas mixesSolution diffuse Heat flow hot →cold
X X X
Reactant Product
∆Hsys
θ = ∑∆Hf
θ
(pro) - ∑∆Hf
θ
(react)∆Ssys
θ = ∑Sf
θ
(pro) - ∑Sf
θ
(react)
1
308
298
)92000(






JKS
S
T
H
S
surr
surr
surr
kJHsys 92)0(92 
surrsysuni SSS 
1
107308201 


JKS
SSS
uni
surrsysuni
Are these rxn at
298K spontaneous?
∆S uni = ∆S sys + ∆S surr
↓
∆S uni > 0 - NH3 production at 298K - Spontaneous
Reactant Product
∆Ssys
θ = ∑Sf
θ
(pro) - ∑Sf
θ
(react) ∆Hsys
θ = ∑∆Hf
θ
(pro) - ∑∆Hf
θ
(react)
kJHsys 168)1564(1732 
1
563
298
)168000(






JKS
S
T
H
S
surr
surr
surr
surrsysuni SSS 
1
52656337 


JKS
SSS
uni
surrsysuni
∆S uni = ∆S sys + ∆S surr
↓
∆S uni > 0 - Decomposition at 298K - Spontaneous
5 6N2(g) + 3H2(g) → 2NH3(g)
N2(g) + 3H2 (g) → 2NH3(g)
∆Hf
0 0 0 - 46 x 2
S0 + 192 + 131 x 3 + 192 x 2
1
)tan()(
201
585384




JKS
S
SSS
sys
sys
treacproductsys
4KCIO3(s) → 3KCIO4(s) + KCI(s)
4KCIO3(s) → 3KCIO4(s) + KCI(s)
∆Hf
0 - 391 x 4 - 432 x 3 - 436
S0 + 143 x 4 + 151 x 3 + 82
1
)tan()(
37
572535




JKS
S
SSS
sys
sys
treacproductsys

25. 1
118
1500
)178000(






JKS
S
T
H
S
surr
surr
surr
Entropy
Why gas mixes and not unmix?Why conc solution diffuse and not undiffuse? Why heat flow from hot to cold?
Predict entropy change - quatitatively
Gas mixesSolution diffuse Heat flow hot →cold
X X X
Reactant Product
∆Hsys
θ = ∑∆Hf
θ
(pro) - ∑∆Hf
θ
(react)∆Ssys
θ = ∑Sf
θ
(pro) - ∑Sf
θ
(react)
kJHsys 178)1206(1028 
surrsysuni SSS 
1
437597160 


JKS
SSS
uni
surrsysuni
∆S uni = ∆S sys + ∆S surr
↓
∆S uni < 0 - Decomposition at 298K - Non Spontaneous
Reactant Product
∆Ssys
θ = ∑Sf
θ
(pro) - ∑Sf
θ
(react) ∆Hsys
θ = ∑∆Hf
θ
(pro) - ∑∆Hf
θ
(react)
surrsysuni SSS 
1
42118160 


JKS
SSS
uni
surrsysuni
∆S uni = ∆S sys + ∆S surr
↓
∆S uni > 0 - Decomposition at 1500K - Spontaneous
7 8CaCO3 (s) → CaO(s) + CO2(g)
CaCO3 (s) → CaO (s) + CO2(g)
∆Hf
0 - 1206 - 635 - 393
S0 + 93 + 40 + 213
1
)tan()(
160
93253




JKS
S
SSS
sys
sys
treacproductsys
Decomposition at 298K Decomposition at 1500K
CaCO3 (s) → CaO(s) + CO2(g)
CaCO3 (s) → CaO (s) + CO2(g)
∆Hf
0 - 1206 - 635 - 393
S0 + 93 + 40 + 213
1
)tan()(
160
93253




JKS
S
SSS
sys
sys
treacproductsys kJHsys 178)1206(1028 
Rxn Temp dependent
Spontaneousat High ↑Temp
Decomposition limestone
CaCO3 spontaneous?
1
597
298
)178000(






JKS
S
T
H
S
surr
surr
surr

26. Entropy
Why gas mixes and not unmix?Why conc solution diffuse and not undiffuse? Why heat flow from hot to cold?
Predict entropy change - quatitatively
Gas mixesSolution diffuse Heat flow hot →cold
X X X
Reactant Product
∆Hsys
θ = ∑∆Hf
θ
(pro) - ∑∆Hf
θ
(react)∆Ssys
θ = ∑Sf
θ
(pro) - ∑Sf
θ
(react)
1
)tan()(
22
7048




JKS
S
SSS
sys
sys
treacproductsys kJHsys 6)286(292 
surrsysuni SSS 
1
22022 


JKS
SSS
uni
surrsysuni
Is Freezing
spontaneous?
Unit for ∆S - JK-1 Unit for ∆H -
kJ
∆S uni = ∆S sys + ∆S surr
↓
∆S uni < 0 - Freezing at 298K - Non Spontaneous
Reactant Product
∆Ssys
θ = ∑Sf
θ
(pro) - ∑Sf
θ
(react) ∆Hsys
θ = ∑∆Hf
θ
(pro) - ∑∆Hf
θ
(react)
1
)tan()(
22
7048




JKS
S
SSS
sys
sys
treacproductsys kJHsys 6)286(292 
1
8.22
263
)6000(






JKS
S
T
H
S
surr
surr
surr
surrsysuni SSS 
1
8.08.2222 


JKS
SSS
uni
surrsysuni
∆S uni = ∆S sys + ∆S surr
↓
∆S uni > 0 -Freezing at 263K - Spontaneous
9 10H2O (l) → H2O(s) H2O (l) → H2O(s)
H2O (l) → H2O(s)
∆Hf
0 - 286 - 292
S0 + 70 + 48
H2O (l) → H2O(s)
∆Hf
0 - 286 - 292
S0 + 70 + 48
Freezing at 298K (25C)
Freezing at 263K (-10C)
Rxn Temp dependent
Spontaneousat Low ↓ temp
1
20
298
)6000(






JKS
S
T
H
S
surr
surr
surr

27. N2O4 (g) → 2NO2(g)
Reactant Product
Entropy
Ice (s) Water (l)
Entropy
Why gas mixes and not unmix?Why conc solution diffuse and not undiffuse? Why heat flow from hot to cold?
Method to calculate entropy
Gas mixesSolution diffuse Heat flow hot →cold
X X X
Qualitatively
Solid → Liquid NaCI(s) → Na+
(aq) + CI -
(aq)N2O4 (g) → 2NO2(g)
Reactant Product
S θ Less More
More microstates
(More dispersion/random/freedom of motion)
Solid → liq → gas
Higher ↑ entropy
Greater number particles in productMore liq/gas in product
Dispersion
EnergyMicrostate
More dispersion of energy
(Electronic, translational, rotational, vibrational, thermal)
Higher entropy ∆S > 0 (+ve) - Spontaneous
∆Ssys
θ = ∑Sf
θ
(pro) - ∑Sf
θ
(react)
∆Srys
θ = More - Less
= +ve > 0
S θ Less More
∆Ssys
θ = ∑Sf
θ
(pro) - ∑Sf
θ
(react)
∆Ssys
θ = More - Less
= +ve > 0
∆Ssys
θ = ∑Sf
θ
(pro) - ∑Sf
θ
(react)
∆Ssys
θ = More - Less
= +ve > 0
NaCI(s) → Na+
(aq) + CI -
(aq)
S θ Less More
Reactant Product
Qualitatively
Unit - J mol -1 K-1

28. Reactant Product
Entropy
Liq N2(l) Gas N2 (g)
Entropy
Why gas mixes and not unmix?Why conc solution diffuse and not undiffuse? Why heat flow from hot to cold?
Method to calculate entropy
Gas mixesSolution diffuse Heat flow hot →cold
X X X
Qualitatively
Liquid → Gas
Reactant Product
S θ Less More
More microstates
(More dispersion/random/freedom of motion)
Solid → liq → gas
Higher entropy
Greater number particles in productMore liq/gas in product
Dispersion
EnergyMicrostate
More dispersion of energy
(Electronic, translational, rotational, vibrational, thermal)
Higher entropy ∆S > 0 (+ve) - Spontaneous
∆Ssys
θ = ∑Sf
θ
(pro) - ∑Sf
θ
(react)
∆Ssys
θ = More - Less
= +ve > 0
S θ Less More
∆Ssys
θ = ∑Sf
θ
(pro) - ∑Sf
θ
(react)
∆Ssys
θ = More - Less
= +ve > 0
∆Ssys
θ = ∑Sf
θ
(pro) - ∑Sf
θ
(react)
∆Ssys
θ = More - Less
= +ve > 0
NH4NO3(s) → NH4
+
(aq) + NO3
-
(aq)
S θ Less More
Reactant Product
Qualitatively
NH4NO3 (s) → NH4
+
(aq) + NO3
-
(aq)
Ba(OH)2 .8H2O(s) + 2NH4NO3 (s) →
Ba2+
(aq) + 2NO3
-
(aq)+ 2NH3 (g) + 10H2O(aq)
Ba(OH)2 .8H2O(s) + 2NH4NO3 (s) → Ba2+
(aq)+ 2NO3
-
(aq)+ 2NH3 (g)+10H2O(aq)
Unit - J mol -1 K-1
+

29. Entropy decrease ↓
Entropy
Why gas mixes and not unmix?Why conc solution diffuse and not undiffuse? Why heat flow from hot to cold?
Predict entropy change - qualitatively
Gas mixesSolution diffuse Heat flow hot →cold
X X X
NH4NO3 (s) → NH4
+
(aq) + NO3
-
(aq)
C3H8(g) + 5O2 (g) → 3CO2(g) + 4H2O(g)2H2(g) + O2 (g) → 2H2O(l)
2Cu(s) + O2 (g) → 2CuO(s)
Br2(l) → Br2(g)
Ag+
(aq) + Br-
(aq) → AgBr(s) H2(g) + CI2 (g) → 2HCI(g)
Cu2+
(aq) + Zn(s) → Cu(s) + Zn2+
(aq) CaCO3 (s) → CaO(s) + CO2(g)
1
Entropy decrease ↓
Entropy decrease ↓
Entropy increase ↑
Entropy increase ↑Entropy increase ↑
Entropy increase ↑
Little change
Little change
2 3
4
Reactant Product
aq - more disorder solid - more order
S higher ↑ S - Lower ↓
Reactant Product
g - more disorder solid - more order
S higher ↑ S - Lower ↓
Reactant Product
Both sides equal number mol gas
Reactant Product
g - more disorder liq - more order
S higher ↑ S - Lower ↓
Reactant Product
liq- more order g - more disorder
S Lower ↓ S - Higher↑
Reactant Product
less g- more order more g - more disorder
S Lower ↓ S - Higher↑
Reactant Product
Both sides equal number mol solid
Reactant Product
solid- more order aq - more disorder
S Lower ↓ S - Higher↑
Reactant Product
solid- more order g - more disorder
S Lower ↓ S - Higher↑
5 6
7 8 9