Entropy – Definition and Pronunciation
What is Entropy?
Entropy of a liquid/gas system remains constant if no heat enters or leaves while it alters its volume or does work but increases or decreases should a small amount of heat enter or leave. Its value is determined by dividing the intrinsic energy of the material by its absolute temperature. The intrinsic energy is the product of specific heat at constant volume multiplied by a change in temperature. Entropy is expressed in heat content per mass per unit of temperature. In the SI system its units are therefore Joule/kg/K. It should be noted that in a reversible process in which there is no heat rejection or absorption, the change of entropy is zero. Entropy is the measure of a system’s thermal energy which is not available for conversion into mechanical work.
Examples of Entropy
Entropy is a thermodynamic quantity used in the study of processes and can be visualized as the degree of disorder of system. It is most useful to consider the change in entropy in a process rather than the absolute entropy values.
From “Liquefied natural gas (LNG) – The Ideal Gas”.
Entropy is a measure of the dispersal of energy within a system and of how close the internal energy of that system is to the absolute minimum value. Entropy is also a measure of the availability of the energy in a system to do work and can be understood as a measure of “before and after” conditions, quantifying how much the energy of the system has been spread out during the process.
From “Gas laws, thermodynamic principles and reliquefaction”.
If heat is added to a material, or removed from it during a reversible process, the quantity of heat transferred, divided by the temperature of the material is called its entropy. Entropy is the dispersion of energy among the molecules of that material.
From “Properties of liquefied gases”.
Pronunciation of Entropy
