Entropy is a measure of the disorder or randomness of a system. It is a thermodynamic property that describes the distribution of energy within a system and its tendency to become more disordered over time.
In thermodynamics, entropy is often expressed as a function of three natural variables: temperature, volume, and pressure. These variables describe the physical state of a system and can be used to calculate the change in entropy during a process.
The formula for finding entropy with three natural variables is given by the equation ΔS = ∫(dq/T), where ΔS is the change in entropy, dq is the infinitesimal amount of heat added to the system, and T is the temperature at which the heat is added.
Entropy can be calculated experimentally by measuring the change in temperature and volume of a system while adding a known amount of heat. These values can then be used in the formula ΔS = ∫(dq/T) to determine the change in entropy.
The SI unit for entropy is joules per kelvin (J/K). However, in thermodynamics, it is more common to use the unit of entropy change, which is joules per kelvin per mole (J/(K·mol)).