# Entropy vs. Enthalpy

Thermodynamics is the branch of physics that deals with the study of heat and other relating phenomena. This also deals with the relations of heat with other forms of energy such as electrical, mechanical or chemical energy. Entropy and Enthalpy are the famous terms related to thermodynamics. Entropy is the measurement of the disorder or the randomness in the system during the chemical process, whereas enthalpy measures the heat change or internal energy change of a system during the chemical reaction under constant pressure. Actually, enthalpy is the measure of total energy in the system, although it always denotes the change in the energy system at constant pressure as it as the total enthalpy of the system can’t be measured. It is measured in joules per kilogram. On the other hand, entropy is the measure of random activity, which is usually the amount of disorder in the system. The SI unit for Entropy (S) is Joules per Kelvin (J/K).What is Entropy?Entropy is the measurement of the disorder or the randomness in the system during the chemical process. Actually, it is the measure of random activity, which is usually the amount of disorder in the system. As we know that energy in a body tells about its capability to do work, the energy in a body can be of any type. It can be mechanical, chemical, thermal, nuclear or any other energy. The measure of that change of energy or disorder during the chemical process is entropy. 'S’ denotes entropy, and it is always written as a capital letter. In an equation, it is written as ‘ΔS’ as it represents the disorder in the entropy during the chemical process. The SI unit for Entropy (S) is Joules per Kelvin (J/K). The temperature in the entropy equation is measured on the absolute or Kelvin temperature scale. ## Comparison Chart

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Entropy is the measurement of the disorder or the randomness in the system during the chemical process.
Enthalpy measures the heat change or internal energy change of a system during the chemical reaction under constant pressure.

### SI unit

Unit joule per kelvin (J/K)
The SI unit for specific enthalpy is joule per kilogram.

S=q/T
H=U+PV

## Entropy and Enthalpy Definitions

#### Entropy

Symbol S For a closed thermodynamic system, a quantitative measure of the amount of thermal energy not available to do work.

#### Enthalpy

Symbol H A thermodynamic function of a system, equivalent to the sum of the internal energy of the system plus the product of its volume multiplied by the pressure exerted on it by its surroundings.

#### Entropy

A measure of the disorder or randomness in a closed system.

#### Enthalpy

A measure of the heat content of a chemical or physical system.
$H = U + p V$, where H is enthalpy, U is internal energy, p is pressure, and V is volume.

#### Entropy

A measure of the loss of information in a transmitted message.

#### Enthalpy

(thermodynamics) a thermodynamic quantity equal to the internal energy of a system plus the product of its volume and pressure;
Enthalpy is the amount of energy in a system capable of doing mechanical work

#### Entropy

The tendency for all matter and energy in the universe to evolve toward a state of inert uniformity.

#### Entropy

The deterioration of a system or society, especially when it seems inevitable
City activists who fought entropy by organizing neighborhood groups.

#### Entropy

A measure of the disorder present in a system.

#### Entropy

(Boltzmann definition) A measure of the disorder directly proportional to the natural logarithm of the number of microstates yielding an equivalent thermodynamic macrostate.

#### Entropy

(information theory) Shannon entropy

#### Entropy

A measure of the amount of energy in a physical system that cannot be used to do work.

#### Entropy

The capacity factor for thermal energy that is hidden with respect to temperature.

#### Entropy

The dispersal of energy; how much energy is spread out in a process, or how widely spread out it becomes, at a specific temperature.

#### Entropy

A measure of the amount of information and noise present in a signal.

#### Entropy

(uncountable) The tendency of a system that is left to itself to descend into chaos.

#### Entropy

A certain property of a body, expressed as a measurable quantity, such that when there is no communication of heat the quantity remains constant, but when heat enters or leaves the body the quantity increases or diminishes. If a small amount, h, of heat enters the body when its temperature is t in the thermodynamic scale the entropy of the body is increased by h ÷ t. The entropy is regarded as measured from some standard temperature and pressure. Sometimes called the thermodynamic function.
The entropy of the universe tends towards a maximum.

#### Entropy

(communication theory) a numerical measure of the uncertainty of an outcome;
The signal contained thousands of bits of information

#### Entropy

(thermodynamics) a thermodynamic quantity representing the amount of energy in a system that is no longer available for doing mechanical work;
Entropy increases as matter and energy in the universe degrade to an ultimate state of inert uniformity

What is Enthalpy?

Enthalpy measures the heat change or internal energy change of a system during the chemical reaction under constant pressure. Enthalpy is the measure of total energy in the system, although it always denotes the change in the energy system at constant pressure as it as the total enthalpy of the system can’t be measured. Enthalpy is denoted as ‘ΔH,.’ It tells about the difference between the enthalpy of the products and the enthalpy of the reactants. It is measured in the units of Jmol-1. The word enthalpy is derived from the Greek word ‘enthalpos,’ meaning ‘to put heat into’. The word ‘enthalpy’ for this measure was coined by a 19th-century famous physicist Heike Kamerlingh Onnes. It is generally measured in joules per kilogram.

Entropy vs. Enthalpy

• Entropy is the measurement of the disorder or the randomness in the system during the chemical process, whereas enthalpy measures the heat change or internal energy change of a system during the chemical reaction under constant pressure.
• Actually, enthalpy is the measure of total energy in the system, whereas entropy is the measure of random activity, which is usually the amount of disorder in the system.
• The word ‘enthalpy’ for this measure was coined by a 19thcentury famous physicist Heike Kamerlingh Onnes, on the other hand, German physicist Rudolf Clausius coined the word ‘entropy.’

Explanatory Video