Todays lecture objectives:

1
ATMS 305 Atmospheric Thermodynamics and Statics

• Todays lecture objectives
• Thermodynamic Functions and Equilibrium
  Conditions (WH 2.9)
• How do I know if a system is in equilibrium?

?
2
ATMS 305 Thermodynamic Functions and
Equilibrium Conditions

• Todays lecture topics
• Thermodynamic Functions and Equilibrium
  Conditions (WH 2.9)
• Entropy and equilibrium
• Thermodynamic Potentials
• Helmholtz free energy
• Gibbs free energy

3
Second Law of Thermodynamics

• It is impossible for a self-acting machine
  unaided by an external agency to move heat from
  one body to another at a higher temperature

Clausius Statement
(courtesy F. Remer)
4
Second Law of Thermodynamics

• It is impossible to construct a heat engine
  which, while operating in a cycle produces no
  effects except to do work and exchange heat with
  a single reservoir

Kelvin Statement
(courtesy F. Remer)
5
Second Law of Thermodynamics

• Summary

gt0 Irreversible Processes 0 Reversible
Processes lt0 Impossible Processes
DStot
(courtesy F. Remer)
6
Second Law of Thermodynamics

• For any natural (irreversible) process
• Final entropy is greater than initial entropy

(courtesy F. Remer)
7
Second Law of Thermodynamics

• System that has attained maximum entropy cannot
  undergo further changes

Hot
Cold
Cool
Lowest Entropy
Highest Entropy
(courtesy F. Remer)
8
Entropy Equilibrium

• Entropy Change

Cool
Hot
Cold
Lowest Entropy Changes with Time
Highest Entropy Does Not Change
(courtesy F. Remer)
9
Second Law of Thermodynamics

• State of maximum entropy is a state of
  equilibrium!

Hot
Cold
Cool
Lowest Entropy
Highest Entropy
(courtesy F. Remer)
10
Entropy Equilibrium

• Equilibrium
• Properties do not change with time

Hot
Cold
Cool
Not in Equilibrium
Equilibrium
(courtesy F. Remer)
11
ATMS 305 Thermodynamic Functions and
Equilibrium Conditions

• Equilibrium state
• In an equilibrium state every possible
  transformation is reversible and any increase in
  the entropy of a body is equal to the decrease in
  the entropy of its environment
• Necessary condition the total entropy of a body
  and its environment are constant
• How do we apply this??

dS 0
12
Thermodynamic Potentials

• Potential for work to be performed
• Energy above minimum state
• System not in equilibrium

Potential
Minimum State
(courtesy F. Remer)
13
Thermodynamic Potentials

• No potential for work to be performed
• Energy at minimum state
• System in equilibrium

Minimum State
(courtesy F. Remer)
14
Thermodynamic Potentials
Independent variables T, V

• For a system in which temperature and volume are
  not changing with time
• Helmholtz free energy is at minimum
• System is at equilibrium

(courtesy F. Remer)
15
Thermodynamic Potentials
Independent variables T, p

• For a system in which temperature and pressure
  are not changing with time
• Gibbs free energy is at minimum
• System is at equilibrium

(courtesy F. Remer)
16
Thermodynamic Potentials
Independent Variables

• Summary

S, V
S, p
T, V
T, p
(courtesy F. Remer)
17
Thermodynamic Potentials

• At Equilibrium

Maxwell Relations
(courtesy F. Remer)
18
Thermodynamic Potentials

• Independent Variables

(courtesy F. Remer)
19
(No Transcript)