Thermodynamics
•Concerns the study of the Equilibrium properties (or quasi-static equilibrium)
of a system and its surroundings.
•Temperature is a variable, and heat and work are somehow involved.
• Heat is energy in transit.
Surroundings
System
Mass
The above system is open.
Universe
Thermodynamics
•Concerns the study of the Equilibrium properties (or quasi-static equilibrium)
of a system and its surroundings.
•Temperature is a variable, and heat and work are somehow involved.
• Heat is energy in transit.
Surroundings
System
The above system is closed.
Universe
Thermodynamics
•Concerns the study of the Equilibrium properties (or quasi-static equilibrium)
of a system and its surroundings.
•Temperature is a variable, and heat and work are somehow involved.
• Heat is energy in transit.
Surroundings
System
Mass
The above system is undergoing an adiabatic change.
Universe
Thermodynamics
•Concerns the study of the Equilibrium properties (or quasi-static equilibrium)
of a system and its surroundings.
•Temperature is a variable, and heat and work are somehow involved.
• Heat is energy in transit.
Surroundings
System
The above system is isolated.
Universe
Thermodynamics
•Concerns the study of the Equilibrium properties (or quasi-static equilibrium)
of a system and its surroundings.
•Temperature is a variable, and heat and work are somehow involved.
• Heat is energy in transit.
Surroundings
Universe
System
System Wall
The above system is isolated.
Thermodynamics
•Concerns the study of the Equilibrium properties (or quasi-static equilibrium)
of a system and its surroundings.
•Temperature is a variable, and heat and work are somehow involved.
• Heat is energy in transit.
Surroundings
Universe
System
System Wall
The above is an example of a diathermal wall.
Equations of state
•An equation of state is a mathematical relation between state
variables, e.g. p, V & T.
•This reduces the number of independent variables to two.
General form: f (p,V,T) = 0
Example:
pV – nRT = 0
(ideal gas law)
•Defines a 2D surface in p-V-T state space.
•Each point on this surface represents an unique state of the system.
f (p,V,T) = 0
Equilibrium state:
macroscopic variables
do not change in time!
Joule’s apparatus for measuring the mechanical equivalent of heat
1 cal = 4.184 J will raise temperature of water by 1 C (14.5 C to 15.5 C)
Specific heats of ideal gases
• Now that we have an expression for the internal energy of an ideal gas, we
can calculate the specific heats:
du f
 u 
cv  
 R
 
 T v dT 2
cP
 
cv

f
2
f
f

cP  cv  R    1 R
2 
  f 2
1
2
f
f
 3 .