Thermodynamic Terms, Functions and Relations

Common thermodynamic terms and functions - potential energy, kinetic energy, thermal or internal energy, chemical energy, nuclear energy and more

  • Chemical energy - is related to the relationships between molecules in chemical compounds. When chemicals react with each other, they may give off heat (exothermic reaction) or require heat (endothermic reaction)
  • Electric energy - is related to electrons moving through a conductor
  • Energy - can be reduced to the concepts of heat and work and can be found in various forms: potential energy, kinetic energy, thermal or internal energy, chemical energy, and nuclear energy
  • Enthalpy - is a term with energy units that combines internal energy with a pressure/volume or flow work term
  • Entropy - is a property of matter that measures the degree of randomization or disorder. The natural state is for entropy to be produced by all processes
  • Heat - is energy in motion from one region to an other as a result of temperature difference
  • Internal energy - has to do with activity within the molecular structure and is typically observed with temperature measurement
  • Kinetic energy - is the energy of motion and is proportional to the square of the velocity as well to the mass of the moving body
  • Nuclear energy - is related to the energy of atomic relationships between the fundamental particles. Nuclear fission and fusion are reactions which release nuclear energy
  • Potential energy - is the energy of location or position of a mass in a force field
  • Property - is a measurable characteristic of a system or substance. Temperature, density, pressure etc
  • Specific Heat - The specific heat is the amount of heat required to change a unit mass (or unit quantity, such as mole) of a substance by one degree in temperature
  • Temperature - is a term used to quantify the difference between warm and cold level of internal energy of a substance
  • Work - is an energy form which can be equated to the rising of a weight as moving a mass in a force field or moving a liquid against a resisting force

See also Symbols Used to Denote a Chemical Reaction, Process or Condition

Term Function
Activity coefficient γi = fi/(xifiθ)
Chemical potential μi = (∂G/∂ni)T,p,nj≠i
Energy U
Enthalpy H = U + pV
Entropy S
Fugasity fi = (xi)exp{(μi - μiÞg)/RT}
Gibbs (free) energy G = U + pV - TS
Gibbs-Duhem relation 0 = SdT - Vdp + Σinidμi
Gibbs-Helmholtz equation H = G - T(∂G/∂T)p
Helmholtz energy A = U - TS
Isentropic (constant heat and mass) compressibility κS = - (∂V/∂p)S/V
Isothermal (constant temperature) compressibility κT = - (∂V/∂p)T/V
κT - κS  = T αV2V/Cp
Isobaric (constant pressure) expansivity αV= (∂V/∂T)p/V
Isobaric heat capacity Cp = (∂H/∂T)p
Isochoric (constant volume) heat capacity CV = (∂U/∂T)v
Cp - CV = Tα2V/κT
Joule-Thompson expansion μJT = (∂T/∂p)H = - {V - (∂V/∂T)p}/Cp
ΦJT = (∂H/∂p)T = V - T(∂V/∂T)p
Maxwell relations (∂S/∂p)T = - (∂V/∂p)p
(∂S/∂V)T = - (∂p/∂T)V
Partial molar quantity Xi = (∂X/∂ni)T,p,nj≠i
Perfect (ideal) gas [symbol Þg] pV = (Σini)RT
μiÞg = μiθ + RTln(xip/pθ)


p = pressure
V = Volume
T = temperature
ni = amount of substance i
xi = nijnj = mole fraction of substance i
= gas constant

Related Topics

Related Documents

  • Properties and State - Concept of properties and state
  • 1st Law of Thermodynamics - The First Law of Thermodynamics simply states that energy can be neither created nor destroyed (conservation of energy). Thus power generation processes and energy sources actually involve conversion of energy from one form to another, rather than creation of energy from nothing
  • 2nd Law of Thermodynamics - The second law is concerned with entropy, which is a measure of disorder. The second law says that the entropy of the universe increases
  • Third Law of Thermodynamics - The entropy of a substance is zero if the absolute temperature is zero
  • Universal and Individual Gas Constants - The Universal and Individual Gas Constants in fluid mechanics and thermodynamics
  • Water - Thermodynamic Properties - Thermal properties of water - density, freezing temperature, boiling temperature, latent heat of melting, latent heat of evaporation, critical temperature and more
  • Air Properties - Density, specific heat, thermal conductivity, expansion coefficient, kinematic viscosity and Prandtl's number - air temperature ranging -150 oC to 400 oC
  • Heat Capacity - The heat capacity of a substance is the amount of heat required to change its temperature by one degree, and has units of energy per degree
  • Symbols Used to Denote a Chemical Reaction, Process or Condition - Explanation of symbols used as subscripts or superscripts to tell more about the type of chemical reaction, process or condition
  • Dimensionless numbers - Definitions and symbols for physical and chemical dimensionless quantities, with areas of application of the different numbers. Reynolds, Euler, Nusselt, Prandtl..... and many more
  • Melting and Boiling Point, Density and Solubility in Water for Inorganic Compounds - Physical constants for more than 280 common inorganic compounds. Density is given for the actual state at 25°C and for liquid phase at melting point temperature.
  • Heat of combustion - Tabulated values of heat of combustion (= energy content) of common substances, together with examples showing how to calculate the heat of combustion
  • WABT - weighted average bed temperature - Definition and examples of calculation of weighted average bed temperature in adiabatic reactors

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