KT (energy)
Encyclopedia
kT is the product of the Boltzmann constant, k, and the temperature
, T. This product is used in physics
as a scaling factor for energy
values in molecular
-scale systems (sometimes it is used as a unit of energy), as the rates and frequencies of many processes and phenomena depend not on their energy alone, but on the ratio of that energy and kT, that is, on E / kT (see Arrhenius equation
, Boltzmann factor
). For a system in equilibrium in canonical ensemble
, the probability of the system being in energy E is given by e-ΔE / kT. More fundamentally, kT is the amount of heat
required to increase the thermodynamic entropy
of a system, in natural units, by one nat
.
In macroscopic scale systems, with large numbers of molecules, RT
value is commonly used; its SI units are joules per mole (J/mol
): (RT = kT * NA
). At room temperature 25 °C (77 °F, 298 K) 1kT is equivalent to 4.11x10−21 J , 4.11 pN·nm , 9.83x10−22 cal, 0.0256 eV, 2.479 kJ·mol−1
or 0.593 kcal·mol−1
.
Temperature
Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...
, T. This product is used in physics
Physics
Physics is a natural science that involves the study of matter and its motion through spacetime, along with related concepts such as energy and force. More broadly, it is the general analysis of nature, conducted in order to understand how the universe behaves.Physics is one of the oldest academic...
as a scaling factor for energy
Energy
In physics, energy is an indirectly observed quantity. It is often understood as the ability a physical system has to do work on other physical systems...
values in molecular
Molecule
A molecule is an electrically neutral group of at least two atoms held together by covalent chemical bonds. Molecules are distinguished from ions by their electrical charge...
-scale systems (sometimes it is used as a unit of energy), as the rates and frequencies of many processes and phenomena depend not on their energy alone, but on the ratio of that energy and kT, that is, on E / kT (see Arrhenius equation
Arrhenius equation
The Arrhenius equation is a simple, but remarkably accurate, formula for the temperature dependence of the reaction rate constant, and therefore, rate of a chemical reaction. The equation was first proposed by the Dutch chemist J. H. van 't Hoff in 1884; five years later in 1889, the Swedish...
, Boltzmann factor
Boltzmann factor
In physics, the Boltzmann factor is a weighting factor that determines the relative probability of a particle to be in a state i in a multi-state system in thermodynamic equilibrium at temperature T...
). For a system in equilibrium in canonical ensemble
Canonical ensemble
The canonical ensemble in statistical mechanics is a statistical ensemble representing a probability distribution of microscopic states of the system...
, the probability of the system being in energy E is given by e-ΔE / kT. More fundamentally, kT is the amount of heat
Heat
In physics and thermodynamics, heat is energy transferred from one body, region, or thermodynamic system to another due to thermal contact or thermal radiation when the systems are at different temperatures. It is often described as one of the fundamental processes of energy transfer between...
required to increase the thermodynamic entropy
Entropy
Entropy is a thermodynamic property that can be used to determine the energy available for useful work in a thermodynamic process, such as in energy conversion devices, engines, or machines. Such devices can only be driven by convertible energy, and have a theoretical maximum efficiency when...
of a system, in natural units, by one nat
Nat (information)
A nat is a logarithmic unit of information or entropy, based on natural logarithms and powers of e, rather than the powers of 2 and base 2 logarithms which define the bit. The nat is the natural unit for information entropy...
.
In macroscopic scale systems, with large numbers of molecules, RT
RT (energy)
RT is the product of the molar gas constant, R, and the temperature, T. This product is used in physics as a scaling factor for energy values in macroscopic scale , as many processes and phenomena depend not on the energy alone, but on the ratio of energy and RT, i.e. E/RT...
value is commonly used; its SI units are joules per mole (J/mol
Mole (unit)
The mole is a unit of measurement used in chemistry to express amounts of a chemical substance, defined as an amount of a substance that contains as many elementary entities as there are atoms in 12 grams of pure carbon-12 , the isotope of carbon with atomic weight 12. This corresponds to a value...
): (RT = kT * NA
Avogadro's number
In chemistry and physics, the Avogadro constant is defined as the ratio of the number of constituent particles N in a sample to the amount of substance n through the relationship NA = N/n. Thus, it is the proportionality factor that relates the molar mass of an entity, i.e...
). At room temperature 25 °C (77 °F, 298 K) 1kT is equivalent to 4.11x10−21 J , 4.11 pN·nm , 9.83x10−22 cal, 0.0256 eV, 2.479 kJ·mol−1
Joule per mole
The joule per mole is an SI derived unit of energy per amount of material. Energy is measured in joules, and the amount of material is measured in moles....
or 0.593 kcal·mol−1
Kilocalorie per mole
The kilocalorie per mole is a derived unit of energy per Avogadro’s number of particles. It is the quotient of a kilocalorie and a mole, mainly used in the United States....
.