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Specific entropy may be expressed relative to a unit of mass, typically the kilogram (unit: J⋅kg −1 ⋅K −1 ). Alternatively, in chemistry, it is also referred to one mole of substance, in which case it is called the molar entropy with a unit of J⋅mol −1 ⋅K −1 .
In statistical thermodynamics the most general formula for the thermodynamic entropy S of a thermodynamic system is the Gibbs entropy S = − k B ∑ p i ln p i , {\displaystyle S=-k_{\text{B}}\sum p_{i}\ln p_{i}\,,}
In statistical mechanics, Boltzmann's equation (also known as the Boltzmann–Planck equation) is a probability equation relating the entropy, also written as , of an ideal gas to the multiplicity (commonly denoted as or ), the number of real microstates corresponding to the gas's macrostate:
The second law of thermodynamics states that the total entropy of a system either increases or remains constant in any spontaneous process; it never decreases. An important implication of this law is that heat transfers energy spontaneously from higher- to lower-temperature objects, but never spontaneously in the reverse direction.
May 29, 2024 · Entropy, the measure of a system’s thermal energy per unit temperature that is unavailable for doing useful work. Because work is obtained from ordered molecular motion, entropy is also a measure of the molecular disorder, or randomness, of a system.
Sep 12, 2022 · Entropy, like internal energy, is a state function. This means that when a system makes a transition from one state into another, the change in entropy \(\Delta S\) is independent of path and depends only on the thermodynamic variables of the two states.
Nov 28, 2021 · In physical chemistry and thermodynamics, one useful entropy formula relates entropy to the internal energy (U) of a system: dU = T dS – p dV. Here, the change in internal energy dU equals absolute temperature T multiplied by the change in entropy minus external pressure p and the change in volume V.
Entropy behaves in predictable ways. In Physics the basic definition is: S = k B log(Ω) Where: S is entropy; k B is Boltzmann's Constant (1.380649×10 −23 J/K) Ω is the number of "Microstates" Another important formula is: ΔS = QT. Where: ΔS is the change in entropy; Q is the flow of heat energy in or out of the system; T is temperature
Jul 3, 2019 · Put simply entropy is a measure of the number of ways to distribute energy to one or more systems, the more ways to distribute the energy the more entropy a system has. Dots represent energy quanta and are distributed among 3 wells representing the 3 ways an atom can store energy. Ω = 6.
The second law of thermodynamics is best expressed in terms of a change in the thermodynamic variable known as entropy, which is represented by the symbol S. Entropy, like internal energy, is a state function.
