Fundamental of Thermodynamic: Definition & Laws -Embibe
  • Written By Monica_Kumari
  • Last Modified 22-07-2022
  • Written By Monica_Kumari
  • Last Modified 22-07-2022

Fundamental of Thermodynamic: Basic Concepts & Laws

Fundamental of Thermodynamics: Thermodynamics is concerned with the concepts of heat and temperature, as well as the interaction between heat and other types of energy. In general, thermodynamics is associated with the transportation of energy from one location to another and from one form to another. We have discussed the fundamental of thermodynamic along with their laws in this article.

The word thermodynamics was invented in 1749 by William Thomson. The four thermodynamic laws control and precisely describe the behaviour of these quantities. Read this article carefully to have a thorough understanding of the basic concepts of thermodynamics.

What is Thermodynamics?

Thermodynamics is a discipline of physics that studies heat, work, and temperature and their relationships to energy, radiation, and the physical properties of matter. It should be noted that thermodynamics is a macroscopic science. This means that it is concerned with the bulk system rather than the molecular structure of matter.

It discusses how thermal energy is transformed to or from other forms of energy, as well as how this process affects matter. Thermal energy is energy derived from heat. The movement of microscopic particles within an object generates heat, and the faster these particles move, the more heat is generated. Scroll down to learn more about the fundamental of thermodynamic.

Fundamental of Thermodynamics

Thermodynamics is coupled with its own terminology. Thorough knowledge of the fundamental of thermodynamic creates the basis for a solid understanding of the various topics covered in thermodynamics, avoiding possible confusion.

Thermodynamic Systems

System, surroundings, and boundary


A thermodynamic system is a particular portion of matter with a defined boundary on which we focus our interest. The system boundary can be real or imaginary, fixed or deformable.

Types of Systems

Systems are classified into three types:

1. Isolated System: An isolated system is incapable of exchanging energy or mass with its surroundings. The universe is regarded as an isolated system.
2. Closed System: The transmission of energy occurs across the closed system’s boundary, but the transfer of mass does not. Closed systems include refrigerators and gas compression in piston-cylinder assemblies.
3. Open System: Mass and energy can both be moved between the system and its surroundings in an open system. An open system is illustrated by a steam turbine.

Interactions of Thermodynamic Systems:

Type of SystemMass FlowWorkHeat
Isolated System
Open System
Closed System


A surrounding is anything outside the system that has a direct influence on the system’s behaviour.


A boundary is a closed surface that surrounds a system and allows energy or mass to enter or exit the system. A system’s boundaries can be fixed or flexible. The boundary is mathematically thin, massless, and volumeless.

Thermodynamic Process

A thermodynamic process occurs when there is an energetic shift within a system that is correlated with variations in pressure, volume, and internal energy.

There are four types of thermodynamic processes, each with its own set of characteristics, and they are as follows:

1. Adiabatic Process: A process in which no heat is transferred into or out of the system.
2. Isochoric Process: A mechanism in which there is no change in volume and the system does no work.
3. Isobaric Process: A procedure in which there is no change in pressure.
4. Isothermal Process: A mechanism in which there is no change in temperature.

Read More: Heat and Thermodynamics

Thermodynamic Equilibrium

All characteristics of a system have constant values at any given state. As a result, if the value of even one attribute changes, the system’s state changes. When an equilibrium system is isolated from its surroundings, no changes in the value of its attributes occur.

  • When the temperature remains constant throughout the system, we say it is in thermal equilibrium.
  • We consider the system to be in mechanical equilibrium when there is no variation in pressure at any point in the system.
  • When the chemical composition of a system does not change over time, the system is said to be in chemical equilibrium.
  • In a two-phase system, phase equilibrium occurs when the mass of each phase approaches an equilibrium level.

If a thermodynamic system is in chemical equilibrium, mechanical equilibrium, and thermal equilibrium, and the relevant parameters no longer change with time, it is said to be in thermodynamic equilibrium.

Thermodynamic Properties

Thermodynamic properties are defined as system characteristics that can describe the system’s state. Thermodynamic properties can be extensive or intensive.

1. Intensive Properties

Intensive properties are those that are independent of a system’s size (mass). They do not complement each other. Example: Temperature, Pressure, and Density

2. Extensive Properties

Extensive properties are those which depend on system size, such as mass, volume, and total energy U. They are additive in nature.

Intensive and extensive properties of a system- fundamental of thermodynamic
  • In general, capital letters represent extensive attributes (excluding mass m) while lowercase letters denote intensive properties (except pressure P, temperature T).
  • Extensive properties are those that have numerous attributes per unit mass, such as specific volume (v=V/m).

Laws of Thermodynamics

The fundamental physical quantities such as energy, temperature, and entropy that describe thermodynamic systems at thermal equilibrium are described under thermodynamic laws. These thermodynamic principles represent how these quantities react under different conditions.

The following are the four laws of thermodynamics:

1. Zeroth Law of Thermodynamics: When two systems are in thermal equilibrium with a third system, the first two systems are also in thermal equilibrium with one another. This characteristic makes using thermometers as the “third system” and creating a temperature scale reasonable.
2. First Law of Thermodynamics: The first law of thermodynamics is often known as the law of conservation of energy. The difference between heat provided to the system from its surroundings and work done by the system in its surroundings equals the change in the internal energy of a system.
3. Second Law of Thermodynamics: Heat does not spontaneously move from a colder zone to a hotter zone, and heat at a particular temperature cannot be completely turned into work. As a result, the entropy of a closed system, or heat energy per unit temperature, rises with time, eventually reaching a maximum value. Therefore, all closed systems move toward an equilibrium state with maximum entropy and no energy available to conduct useful work.
4. Third Law of Thermodynamics: As the temperature approaches absolute zero, the entropy of a perfect crystal of an element in its most stable state tends to zero. This enables the establishment of an absolute scale for entropy, that, from a statistical standpoint, indicates the degree of randomness or disorder in a system.

Fundamental of Thermodynamic Potentials

Thermodynamic potentials are quantitative measures of a system’s stored energy. Potentials assess the energy variations in a system as it transforms from its initial to the final state. Depending on the system restrictions, such as temperature and pressure, different potentials are used.

The following are several instances of thermodynamic potentials and associated formulas:

Internal EnergyΔU = λ − PΔV
Helmholtz free energyF = U – TS
EnthalpyH = U + PV
Gibbs Free EnergyG = U + PV – TS

Thermodynamics Applications in Daily Life

The use of thermodynamics is everywhere, whether we are sitting in an air-conditioned room or driving in any vehicle. A couple of these applications are mentioned below:

  • The 2nd law of thermodynamics governs the operation of several types of transportation such as aeroplanes, trucks, and ships.
  • The three ways of heat transmission operate using thermodynamics. Radiators, heaters, and coolers all use heat transfer concepts.
  • Thermodynamics is used in the study of various types of power plants, including nuclear power plants and thermal power plants.

Stay tuned to for a better understanding of other concepts.

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