Lecture Notes on Thermodynamics and Entropy

Flashcards on Thermodynamics, Enthalpy, Entropy, and the Microscopic View of Entropy

Second Law of Thermodynamics

It is impossible to obtain an equal amount of work out of a system relative to the energy put into it under isothermal reversible conditions.

Real System

Any spontaneous process occurring without outside intervention.

Entropy

Inevitable increase for a real process until it reaches a maximum, leading to the heat death of the Universe.

ΔS univ

The entropy of the universe always increases for a real process.

ΔH vap

The change in enthalpy when a substance transitions from liquid to gas.

ΔH cond

The change in enthalpy when a substance transitions from gas to liquid.

Methane

Heat of vaporization for methane is 8.17 kJ/mole, and its boiling point is -162 °C.

ΔS sys

The entropy change associated with methane going from a gas to a liquid.

Kinetic Molecular Theory (KMT)

Atoms exist, they have mass and velocity; KE is related to velocity.

Boltzmann's Discovery

Over time, any distribution of gas energies will evolve to a Gaussian distribution.

Ludwig Boltzmann

Showed that any distribution of gas energies will evolve to a gaussian.

Boltzmann Equation

S = k_B * ln(Ω), relates entropy to the number of microstates.

Microstate

Arrangement of position and energy of a system.

Entropy

Number of equivalent configurations (energy & location) of a state.

Entropy and Configurations

More configurations, higher S; more configurations, more likely the state.

2nd Law of Thermodynamics

ΔS univ = ΔS sys + ΔS surr : The entropy of the universe always increases.

Degrees of Freedom

Number of ways a molecule can move (translate), rotate, and vibrate.

Degrees of Freedom Calculation

3N-5 for linear molecules, 3N-6 for non-linear molecules (N = # nuclei in molecule).