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A thermodynamic state is a set of values of properties of a thermodynamic
Thermodynamics

In physics, thermodynamics is the study of the conversion of heat energy into different forms of energy ; different energy conversions into heat energy; and its relation to macroscopic variables such as temperature, pressure, and volume....
 system
Thermodynamic system

In thermodynamics, a thermodynamic system, originally called a working substance, is defined as that part of the universe that is under consideration....
 that must be specified to reproduce the system. The individual parameters are known as state variables, state parameters or thermodynamic variables. Once a sufficient set of thermodynamic variables have been specified, values of all other properties of the system are uniquely determined. The number of values required to specify the state depends on the system, and is not always known.

modynamic variables, also known as state variables or state parameters, describe the momentary condition of a thermodynamic system.






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A thermodynamic state is a set of values of properties of a thermodynamic
Thermodynamics

In physics, thermodynamics is the study of the conversion of heat energy into different forms of energy ; different energy conversions into heat energy; and its relation to macroscopic variables such as temperature, pressure, and volume....
 system
Thermodynamic system

In thermodynamics, a thermodynamic system, originally called a working substance, is defined as that part of the universe that is under consideration....
 that must be specified to reproduce the system. The individual parameters are known as state variables, state parameters or thermodynamic variables. Once a sufficient set of thermodynamic variables have been specified, values of all other properties of the system are uniquely determined. The number of values required to specify the state depends on the system, and is not always known.

Thermodynamic variables

Thermodynamic variables, also known as state variables or state parameters, describe the momentary condition of a thermodynamic system. Regardless of the path by which a system goes from one state to another — i.e., the sequence
Sequence

In mathematics, a sequence is an ordered list of objects . Like a Set , it contains Element , and the number of terms is called the length of the sequence....
 of intermediate states — the total change in any state variable will be the same. This means that the incremental changes in such variables are exact differential
Exact differential

In mathematics, a differential dQ is said to be exact, as contrasted with an inexact differential, if the differentiable function Q exists....
s. Examples of state variables include:
  • Density
    Density

    The density of a material is defined as its mass per unit volume. The symbol of density is ....
     (?)
  • Energy
    Energy

    In physics, energy is a scalar physical quantity that describes the amount of Work_ that can be performed by a force. Energy is an attribute of objects and systems that is subject to a conservation law....
     (E)
  • Helmholtz free energy
    Helmholtz free energy

    In thermodynamics, the Helmholtz free energy is a thermodynamic potential which measures the ?useful? work obtainable from a closed system thermodynamic thermodynamic system at a constant temperature and volume....
     (A)
  • Gibbs free energy
    Gibbs free energy

    In thermodynamics, the Gibbs free energy is a thermodynamic potential that measures the "useful" or process-initiating Work obtainable from an isothermal, Isobaric process thermodynamic system....
     (G)
  • Enthalpy
    Enthalpy

    In thermodynamics and chemistry, the enthalpy is a quotient or description of thermodynamic potential of a system, which can be used to calculate the heat transfer during a quasistatic process taking place in a closed system thermodynamic system under constant pressure....
     (H)
  • Internal energy
    Internal energy

    In thermodynamics, the internal energy of a thermodynamic system, or a physical body with well-defined dimension, denoted by U, or sometimes E, is the total of the kinetic energy due to the motion of molecules and the potential energy associated with the vibrational and electricity energy of atoms within molecules or crysta...
     (U)
  • Mass
    Mass

    In physical science, mass refers to the degree of acceleration a body acquires when subject to a force: bodies with greater mass are accelerated less by the same force....
     (m)
  • Exergy
    Exergy

    In thermodynamics, the exergy of a System is the maximum Mechanical work possible during a Thermodynamic process that brings the system into Thermodynamic equilibrium with a heat reservoir....
  • Pressure
    Pressure

    Pressure is the force per unit area applied to an object in a direction surface normal to the surface. Gauge pressure is the pressure relative to the local atmospheric or ambient pressure....
     (p)
  • Entropy
    Entropy

    In many branches of science, entropy is a measure of the disorder of a system. The concept of entropy is particularly notable as it is applied across physics, information theory and mathematics....
     (S)
  • Temperature
    Temperature

    In physics, temperature is a physical property of a Physical system that underlies the common notions of hot and cold; something that feels hotter generally has the greater temperature....
     (T)
  • Volume
    Volume

    The volume of any solid, liquid, plasma, vacuum or theoretical object is how much three-dimensional space it occupies, often quantified numerically....
     (V)
  • The amounts of each of the chemical
    Chemical compound

    A chemical compound is a Chemical substance consisting of two or more different chemical element Chemical bond together in a fixed mass ratio that can be split into simpler substances....
     components
    Component (thermodynamics)

    In thermodynamics, a component is a chemically distinct constituent ofa system. Calculating the number of components in a system is necessary, for example, when applying Gibbs phase rule in determination of the number of degrees of freedom of a system....
     , expressed as numbers of moles
    Mole (unit)

    The mole is a Units of measurement of amount of substance: it is an SI base unit, and one of the few units used to measure this physical quantity....
     or molecule
    Molecule

    In chemistry, a molecule is defined as a sufficiently stable, electric charge neutral group of at least two atoms in a definite arrangement held together by very strong chemical bonds....
    s


Equilibrium state

Systems found in nature are often dynamic and complex, but in many cases their states are amenable to description based on proximity to ideal conditions. One such ideal condition is that of a stable equilibrium state. Based on many observations, thermodynamics postulates that all systems having no effect on the external environment will change in such a way as to approach unique stable equilibrium states.

Closed simple system

A common example in which the state can be succinctly described is a closed simple system in an equilibrium state. A closed simple system is an ideal system devoid of any internal adiabatic, rigid, or impermeable boundaries and not being acted upon by any external force fields or inertial forces. Based on observation, scientists and engineers have postulated that the state of a simple system at equilibrium can be completely characterized by specifying two independent property variables, such as temperature and pressure, and the masses of the particular chemical species in the system. Relying on this postulate, for many chemical species, phase distribution and intrinsic phase properties such as density, heat capacity, thermal conductivity, viscosity, enthalpy, and entropy have been reproducibly measured and catalogued as functions of temperature and pressure.

See also

  • Excited state
    Excited state

    Excitation is an elevation in energy level above an arbitrary baseline energy state. In physics there is a specific technical definition for energy level which is often associated with an atom being excited to an excited state....
  • Ground state
  • Stationary state
    Stationary state

    In quantum mechanics, a stationary state is an eigenstate of a Hamiltonian , or in other words, a state of definite energy. It is called stationary because the corresponding probability density has no time dependence....