The zeroth law of thermodynamics states that if two thermodynamic systems are each in thermal equilibrium with a third, then all three are in thermal equilibrium with each other. Two systems are said to be in the relation of thermal equilibrium if they are linked by a wall permeable only to heat, and do not change over time. As a convenience of language, systems are sometimes also said to be in a relation of thermal equilibrium if they are not linked so as to be able to transfer heat to each other, but would not do so if they were connected by a wall permeable only to heat. Zeroth law of thermodynamics
Third law of thermodynamics The third law of thermodynamics is sometimes stated as follows:
A thermodynamic system is a precisely specified macroscopic region of the universe, defined by boundaries or walls of particular natures, together with the physical surroundings of that region, which determine processes that are allowed to affect the interior of the region, studied using the principles of thermodynamics. Thermodynamic system
For thermodynamics, a thermodynamic state of a system is fully identified by values of a suitable set of parameters known as state variables, state parameters or thermodynamic variables. Thermodynamic state
A thermodynamic process is the energetic development of a thermodynamic system proceeding from an initial state to a final state. Thermodynamic process
Thermodynamic potential Description and interpretation Five common thermodynamic potentials are: These five common potentials are all energy potentials, but there are also entropy potentials.
In thermodynamics, a thermodynamic system is in thermodynamic equilibrium when it is in thermal equilibrium, mechanical equilibrium, radiative equilibrium, and chemical equilibrium. Thermodynamic equilibrium
A map of global long term monthly average surface air temperatures in Mollweide projection. Temperature
Statistical ensemble (mathematical physics) In mathematical physics, especially as introduced into statistical mechanics and thermodynamics by J. Willard Gibbs in 1902, an ensemble (also statistical ensemble) is an idealization consisting of a large number of virtual copies (sometimes infinitely many) of a system, considered all at once, each of which represents a possible state that the real system might be in. In other words, a statistical ensemble is a probability distribution for the state of the system.
State function The opposite of a state function is a path function. History
Spontaneous process A spontaneous process is the time-evolution of a system in which it releases free energy (usually as heat) and moves to a lower, more thermodynamically stable energy state. The sign convention of changes in free energy follows the general convention for thermodynamic measurements, in which a release of free energy from the system corresponds to a negative change in free energy, but a positive change for the surroundings.
Second law of thermodynamics The second law of thermodynamics states that the entropy of an isolated system never decreases, because isolated systems spontaneously evolve toward thermodynamic equilibrium—the state of maximum entropy.
Reversible process (thermodynamics) In thermodynamics, a reversible process, or reversible cycle if the process is cyclic, is a process that can be "reversed" by means of infinitesimal changes in some property of the system without entropy production (i.e. dissipation of energy). Due to these infinitesimal changes, the system is in thermodynamic equilibrium throughout the entire process. Since it would take an infinite amount of time for the reversible process to finish, perfectly reversible processes are impossible.
Pressure as exerted by particle collisions inside a closed container. Pressure
Partition function (statistical mechanics)
Ideal gas law
Thermodynamic free energy
First law of thermodynamics
Equation of state
Conjugate variables (thermodynamics)