Advance Physics

Thermodynamics
Thermodynamics:

→ Describes macroscopic properties of equilibrium
systems

→ Entirely Empirical

→ Built on 4 Laws and “simple” mathematics



0th Law ⇒ Defines Temperature (T)



1st Law ⇒ Defines Energy (U)



2nd Law ⇒ Defines Entropy (S)



3rd Law ⇒ Gives Numerical Value to Entropy




These laws are UNIVERSALLY VALID, they cannot be circumvented.
Definitions:

• System: The part of the Universe that we choose to study

, 5.60 Spring 2008 Lecture #1 page 1



• Surroundings: The rest of the Universe

• Boundary: The surface dividing the System from the
Surroundings



Systems can be:

• Open: Mass and Energy can transfer between the System and
the Surroundings

• Closed: Energy can transfer between the System and the
Surroundings, but NOT mass

• Isolated: Neither Mass nor Energy can transfer between the
System and the Surroundings

Describing systems requires:

• A few macroscopic properties: p, T, V, n, m, …

• Knowledge if System is Homogeneous or Heterogeneous

• Knowledge if System is in Equilibrium State

• Knowledge of the number of components
Two classes of Properties: