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) |
Where
p = pressure
V = Volume
T = temperature
ni = amount of substance i
xi = ni/Σjnj = mole fraction of substance i
R = gas constant
