Thermodynamics Laws and Concepts

Study Notes

Thermodynamics is the science of energy, derived from the Greek words "therme" (heat) and "dynamis" (power).
Energy is the ability to cause changes.

The 1st law of thermodynamics states that energy is a thermodynamic property, and during an interaction, energy can change from one form to another, but the total amount of energy remains constant.
The 2nd law of thermodynamics asserts that energy has quality as well as quantity, and actual processes occur in the direction of decreasing quality of energy.

Classical thermodynamics is a macroscopic approach that does not require knowledge of individual particles' behavior.
Statistical thermodynamics is a microscopic approach based on the average behavior of large groups of individual particles.

Any physical quantity can be characterized by dimensions.
Units are the magnitudes assigned to the dimensions.
Primary or fundamental dimensions include mass (m), length (L), time (t), and temperature (T).
Secondary or derived dimensions include velocity (V), energy (E), and volume (V), which are expressed in terms of primary dimensions.

A system is any part of the universe that is of interest to us.
The surroundings are everything else in the universe that is not part of the system.
There are three types of systems: open, closed, and isolated.
A boundary is a wall that separates the system and the environment.
Types of boundaries include rigid, non-rigid, permeable, impermeable, semi-permeable, adiabatic, and diathermal.

A property is any characteristic of a system.
Examples of properties include pressure (P), temperature (T), volume (V), and mass (M).
There are two types of properties: intensive and extensive.
Intensive properties are independent of the mass of a system, such as temperature, pressure, and density.
Extensive properties depend on the size or extent of the system.
Specific properties are extensive properties per unit mass.

A system at equilibrium is a system that does not change its state with time.
Examples of equilibrium include a pendulum at rest and a reversible reaction.
A system at equilibrium has a balance of forces, energy, temperature, pressure, or chemical potential that resists outside disturbances.
Equilibrium state is when the concentration of reactants and products are constant over time, and the forward and backward reactions occur at the same rate.
Steady state is when the state variables are constant over time while there is a flow through the system, and the rate of formation and decomposition of a species are equal.
Thermodynamics deals with equilibrium states.