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What is Thermodynamics | Laws, Definition, & Equations | Gurugrah

Thermodynamics | Gurugrah

Thermodynamics –

Thermodynamics is the branch of physics that deals with heat, work, and temperature, and their relation to energy, entropy, and the physical properties of matter and radiation. The behavior of these quantities is governed by the four laws of thermodynamics which give a quantitative description using measurable macroscopic physical quantities but can be explained in terms of microscopic components by statistical mechanics. Thermodynamics applies to a wide variety of disciplines in science and engineering, particularly physical chemistry, biochemistry, chemical engineering, and mechanical engineering, but also in other more complex fields such as meteorology.

Historically, thermodynamics developed out of a desire to increase the efficiency of early steam engines, particularly through the work of French physicist Sadi Carnot (1824), who believed that engine efficiency was the key that would allow France to win the Napoleonic Wars. I could help. The Scots-Irish physicist Lord Kelvin was the first to formulate a concise definition of thermodynamics in 1854 which stated, “Thermo-dynamics is the subject of the relation of heat to the forces acting between contiguous parts of bodies, and the heat Relation of electricity agency.

German physicist and mathematician Rudolf Clausius Carnot’s theory came to be known as the Carnot cycle and thus gave a true and strong foundation to the theory of heat. His most important paper, “On the Moving Force of Heat”, published in 1850, first stated the second law of thermodynamics. In 1865 he introduced the concept of entropy. In 1870 he introduced the virial theorem, which applies to heat.

Introduction to thermodynamics –

The description of any thermodynamic system employs the four laws of thermodynamics which form an axiomatic basis. The first law specifies that energy can be transferred between physical systems in the form of heat, as work, and with the transfer of matter. The second law postulates the existence of a quantity called entropy, which describes the direction, thermodynamically, that a system can evolve and measures the order state of a system and is used to measure useful work. Can be removed from the system.

In thermodynamics, the interactions between large groups of objects are studied and classified. At its center is the thermodynamic system and the concepts surrounding it. A system is made up of particles whose average motion defines its properties, And those properties are related to each other through equations of state. The properties can be combined to express internal energy and thermodynamic potential, which are useful for determining conditions for equilibrium and spontaneous processes.

History of thermodynamics –

The history of thermodynamics as a scientific subject usually begins with Otto von Guericke, who designed and built the world’s first vacuum pump in 1650 and demonstrated a vacuum using his Magdeburg hemispheres. Guericke was inspired to create a vacuum in order to refute Aristotle’s long-standing conjecture that ‘nature abhors a vacuum’.

The first thermodynamics textbook was written in 1859 by William Rankin, who originally trained as a physicist and a civil and mechanical engineering professor at the University of Glasgow. Before thermodynamics and Other rules emerged simultaneously in the 1850s, mainly from the works of William Rankine, Rudolf Clausius, and William Thomson (Lord Kelvin). James Clerk Maxwell, Ludwig Boltzmann, Max Planck, Rudolf Clausius, and J. The foundations of statistical thermodynamics were laid by physicists such as Willard Gibbs.

Clausius, who first stated the basic ideas of the second law in his paper “On the Moving Forces of Heat” published in 1850, and has been called “one of the founding fathers of thermodynamics”, introduced the concept of entropy in 1865.

During the years 1873–76 the American mathematical physicist Josiah Willard Gibbs published a series of three papers, the most famous of which is On the Equilibrium of Heterogeneous Substances, in which he showed how thermodynamic processes, including chemical reactions, could be analyzed graphically.

By studying the energy, entropy, volume, temperature, and pressure of a thermodynamic system in this way, one can determine whether a process will occur spontaneously. Pierre Duhem also wrote about chemical thermodynamics in the nineteenth century. During the early 20th century, Gilbert N. Chemists such as Lewis, Merle Randall, and EA Guggenheim applied Gibbs’ mathematical methods to the analysis of chemical processes.

Branches of thermodynamics –

The study of thermodynamic systems has developed into several related branches, each using a different fundamental model as a theoretical or experimental basis, or applying principles to different types of systems.

Classical Thermodynamics –

Classical thermodynamics is the description of states of thermodynamic systems at near-equilibrium, using macroscopic, measurable properties. It is used to model the exchange of energy, work, and heat based on the laws of thermodynamics. The qualifier classical refers to the fact that it represents the first level of understanding of the subject as it developed in the 19th century and describes changes in a system in terms of macroscopic empirical (large-scale, and measurable) parameters. Is.

Statistical Mechanics –

Statistical mechanics, also known as statistical thermodynamics, emerged in the late 19th and early 20th centuries with the development of atomic and molecular theories, and with the explanation of microscopic interactions between individual particles or quantum-mechanical states. Complemented classical thermodynamics. This field relates the microscopic properties of individual atoms and molecules to the macroscopic, bulk properties of materials that can be observed at the human scale, allowing classical thermodynamics to be understood as a natural consequence of statistics, classical mechanics, and quantum theory at the microscopic level. Can go.

Chemical thermodynamics –

Chemical thermodynamics is the study of the interrelation of energy with chemical reactions or with physical changes of state within the limits of the laws of thermodynamics. The primary objective of chemical thermodynamics is to determine the spontaneity of a given change.

Equilibrium Thermodynamics –

Equilibrium thermodynamics is the study of the transfer of matter and energy in systems or bodies that can be operated by agencies in their surroundings, from one state of thermodynamic equilibrium to another. The term ‘thermodynamic equilibrium’ indicates a state of equilibrium in which all macroscopic fluxes are zero; In the case of the simplest systems or bodies, their intensive properties are homogeneous, and their pressures are perpendicular to their boundaries. In an equilibrium state, there are no unbalanced potentials or driving forces between macroscopically separated parts of the system.

Non-equilibrium thermodynamics –

Non-equilibrium thermodynamics is a branch of thermodynamics that deals with systems that are not in thermodynamic equilibrium. Most systems found in nature are not in thermodynamic equilibrium because they are not in a steady state, and are constantly and continuously subject to the flow of matter and energy to and from other systems. The thermodynamic study of non-equilibrium systems requires more general concepts than those dealt with by equilibrium thermodynamics. Many natural systems are still outside the scope of currently known macroscopic thermodynamic methods.

Laws of thermodynamics –

First Law –

The first law of thermodynamics states: In a process without transfer of matter, the change in internal energy, ∆U, of a thermodynamic system is equal to the energy gained as heat, Q minus the thermodynamic work, W, done by the system on its surroundings. Gone.

∆ U = Q – W

Second law –

In macroscopic thermodynamics, the second law is a fundamental observation applicable to any real thermodynamic process; In statistical thermodynamics, the second law is thought to be a consequence of molecular chaos.

Third Law –

The third law of thermodynamics states: As the temperature of a system approaches absolute zero, all processes stop and the entropy of the system reaches a minimum value.

This law of thermodynamics is a statistical law of nature regarding entropy and the impossibility of temperature reaching absolute zero.

“The entropy of all systems and all states of a system is smallest at absolute zero,” or equivalently “it is impossible to reach absolute zero of temperature by any finite number of processes”.

Absolute zero, at which all activity would cease if it were possible to attain it, is −273.15 °C (degrees Celsius), or −459.67 °F (degrees Fahrenheit), or 0 K (Kelvin), or 0° R (degrees Rankine). ) Is )

Axiomatic thermodynamics –

Axiom thermodynamics is a mathematical discipline that aims to describe thermodynamics in terms of rigorous axioms, for example by finding a mathematically rigorous way to express the familiar laws of thermodynamics.

The first attempt at an axiomatic theory of thermodynamics was Constantin Caratheodory’s 1909 work Investigations on the Foundations of Thermodynamics, which used Pfaffian systems and the concept of adiabatic accessibility, a notion introduced by Caratheodory himself. In this formulation, thermodynamic concepts such as heat, entropy, and temperature are derived from quantities that can be measured more directly. The theories that came later differed in the sense that they made assumptions about thermodynamic processes with arbitrary initial and final states, as opposed to considering only neighboring states.

Applied area –

• Atmospheric Thermodynamics

• Biological Thermodynamics

• Black hole thermodynamics

• Chemical Thermodynamics

• Classical Thermodynamics

• Equilibrium Thermodynamics

• Industrial Ecology (Re: Exergy)

• Maximum Entropy Thermodynamics

• Non-equilibrium thermodynamics

• Philosophy of Thermal and Statistical Physics

• Psychometry

• Quantum Thermodynamics

• Statistical thermodynamics, ie statistical mechanics

• Thermoeconomics

• Polymer Chemistry

• Renewable Energy Thermodynamics



By Chanchal Sailani | January 17, 2023, | Editor at Gurugrah_Blogs.



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