Thermodynamics

Vocabulary

absolute zero

minimum possible temperature theoretically achievable, equal to 0 K (–273.15°C), at which there is no particle motion

entropy (S)

measure of the disorder of a system

equilibrium

state in which the forward and reverse reactions are equal

first law of thermodynamics

law that states that energy cannot be created or destroyed, only transformed from one type of energy to another type of energy; given as $\Delta U=q+w$

free energy

capacity of a system to do work

Gibbs free energy (G)

amount of work done by a system, expressed as $G=H-TS$, where H is enthalpy, T is temperature, and S is entropy

macrostate

measurable macroscopic properties of a system

microstate

possible energy and positional configuration of the particles of a system

nonspontaneous change

process in which energy must be added to the system for the change to occur

second law of thermodynamics

law that states that the total entropy of an isolated system only increases over time

spontaneous change

process in which energy is released as a system changes

standard entropy (S°)

entropy of one mole of a substance under standard state conditions, expressed in units J/(K mol)

standard state

set of specific conditions under which reactions are measured, typically 0°C and 1 atm pressure

thermodynamics

branch of physical science that investigates the energy and work of systems

third law of thermodynamics

law that states that the total entropy of a system approaches zero as the temperature of the system approaches absolute zero

work (w)

energy that is transferred when a force acts on an object over a distance

zeroth law of thermodynamics

law that states that when two thermodynamic systems are in thermal equilibrium with a third system, they are in thermal equilibrium with each other