Thermodynamics (from the Greek θερμη, therme, meaning "heat"[1] and δυναμις, dunamis, meaning "power") is a branch of physics and of chemistry that studies the effects of changes in temperature, pressure, and volume on physical systems at the macroscopic scale by analysing the collective motion of their particles using statistics. Greek (el ελληνική γλώσσα or simply el ελληνικά — "Hellenic" is an Indo-European language, spoken today by 15-22 million people mainly In Physics, heat, symbolized by Q, is Energy transferred from one body or system to another due to a difference in Temperature In Physics, power (symbol P) is the rate at which work is performed or energy is transmitted or the amount of energy required or expended for Physics (Greek Physis - φύσις in everyday terms is the Science of Matter and its motion. Chemistry (from Egyptian kēme (chem meaning "earth") is the Science concerned with the composition structure and properties Temperature is a physical property of a system that underlies the common notions of hot and cold something that is hotter generally has the greater temperature Pressure (symbol 'p' is the force per unit Area applied to an object in a direction perpendicular to the surface The volume of any solid plasma vacuum or theoretical object is how much three- Dimensional space it occupies often quantified numerically In Physics the word system has a technical meaning namely it is the portion of the physical Universe chosen for analysis Macroscopic is commonly used to describe physical objects that are measurable and observable by the Naked eye. Statistics is a mathematical science pertaining to the collection analysis interpretation or explanation and presentation of Data. [2][3] Roughly, heat means "energy in transit" and dynamics relates to "movement"; thus, in essence thermodynamics studies the movement of energy and how energy instills movement. In Physics, heat, symbolized by Q, is Energy transferred from one body or system to another due to a difference in Temperature In physics the term dynamics customarily refers to the time evolution of physical processes Historically, thermodynamics developed out of need to increase the efficiency of early steam engines. In Thermodynamics, the thermal efficiency (\eta_{th} \ is a dimensionless performance measure of a thermal device such as an Internal combustion A steam engine is a Heat engine that performs Mechanical work using Steam as its Working fluid. [4]

Typical thermodynamic system, showing input from a heat source (boiler) on the left and output to a heat sink (condenser) on the right. In Thermodynamics, a thermodynamic system, originally called a working substance, is defined as that part of the universe that is under consideration Work is extracted, in this case by a series of pistons. In Thermodynamics, work is the quantity of Energy transferred from one system to another without an accompanying transfer of Entropy.

The starting point for most thermodynamic considerations are the laws of thermodynamics, which postulate that energy can be exchanged between physical systems as heat or work. The laws of thermodynamics, in principle describe the specifics for the transport of Heat and work in Thermodynamic processes. In Physics and other Sciences energy (from the Greek grc ἐνέργεια - Energeia, "activity operation" from grc ἐνεργός In Physics, mechanical work is the amount of Energy transferred by a Force. [5] They also postulate the existence of a quantity named entropy, which can be defined for any system. In Thermodynamics (a branch of Physics) entropy, symbolized by S, is a measure of the unavailability of a system ’s Energy [6] In thermodynamics, interactions between large ensembles of objects are studied and categorized. Central to this are the concepts of system and surroundings. In Thermodynamics, a thermodynamic system, originally called a working substance, is defined as that part of the universe that is under consideration In Thermodynamics, a thermodynamic system, originally called a working substance, is defined as that part of the universe that is under consideration A system is composed of particles, whose average motions define its properties, which in turn are related to one another through equations of state. In Physics and Thermodynamics, an equation of state is a relation between state variables More specifically an equation of state is a thermodynamic Properties can be combined to express internal energy and thermodynamic potentials, which are useful for determining conditions for equilibrium and spontaneous processes. In Thermodynamics, the internal energy of a Thermodynamic system, or a body with well-defined boundaries, denoted by  U, or sometimes  A thermodynamic potential is a Scalar potential function used to represent the Thermodynamic state of a system. A dynamic equilibrium occurs when two opposing Processes proceed at the same rate A spontaneous process is the time-evolution of a system in which it releases free energy (most often as heat and moves to a lower more thermodynamically stable energy state

With these tools, thermodynamics describes how systems respond to changes in their surroundings. This can be applied to a wide variety of topics in science and engineering, such as engines, phase transitions, chemical reactions, transport phenomena, and even black holes. Science (from the Latin scientia, meaning " Knowledge " or "knowing" is the effort to discover, and increase human understanding Engineering is the Discipline and Profession of applying technical and scientific Knowledge and An engine is a mechanical device that produces some form of output from a given input In Thermodynamics, phase transition or phase change is the transformation of a thermodynamic system from one phase to another A chemical reaction is a process that always results in the interconversion of Chemical substances The substance or substances initially involved in a chemical reaction are called The first edition of Transport Phenomena was published in 1960 two years after having been preliminarily published under the title Notes on Transport Phenomena based A black hole is a theoretical region of space in which the Gravitational field is so powerful that nothing not even Electromagnetic radiation (e The results of thermodynamics are essential for other fields of physics and for chemistry, chemical engineering, aerospace engineering, mechanical engineering, cell biology, biomedical engineering, and materials science to name a few. Physics (Greek Physis - φύσις in everyday terms is the Science of Matter and its motion. Chemistry (from Egyptian kēme (chem meaning "earth") is the Science concerned with the composition structure and properties Chemical engineering is the branch of Engineering that deals with the application of Physical science (e Aerospace engineering is the branch of Engineering behind the design construction and science of Aircraft and Spacecraft. Mechanical Engineering is an Engineering discipline that involves the application of principles of physics for analysis Design, Manufacturing See also List of basic cell biology topics. Cell biology (also called cellular biology or formerly cytology, from the Biomedical engineering ( BME) is the application of engineering principles and techniques to the medical field Materials Science or Materials Engineering is an interdisciplinary field involving the properties of matter and its applications to various areas of Science and [7][8]

## History

Sadi Carnot (1796-1832): the father of thermodynamics

A brief history of thermodynamics begins with Otto von Guericke who in 1650 built and designed the world's first vacuum pump and created the world's first ever vacuum (known as the Magdeburg hemispheres). Nicolas Léonard Sadi Carnot (1 June 1796 &ndash 24 August 1832 was a French Physicist and Military engineer who in his 1824 Reflections The history of thermodynamics is a fundamental strand in the History of physics, the History of chemistry, and the History of science in general Otto von Guericke (originally spelled Gericke ˈgeːʁɪkə ( November 20, 1602 &ndash May 11, 1686 ( Julian calendar) A vacuum pump is a device that removes gas molecules from a sealed volume in order to leave behind a partial Vacuum. This vacuum means "absence of matter" or "an empty area or space" for the cleaning appliance see Vacuum cleaner. The Magdeburg hemispheres were a pair of large copper hemispheres with mating rims He was driven to make a vacuum in order to disprove Aristotle's long-held supposition that 'nature abhors a vacuum'. Aristotle (Greek Aristotélēs) (384 BC – 322 BC was a Greek philosopher a student of Plato and teacher of Alexander the Great. Shortly thereafter, Irish physicist and chemist Robert Boyle had learned of Guericke's designs and in 1656, in coordination with English scientist Robert Hooke, built an air pump. Robert Boyle was a Natural philosopher, chemist physicist inventor and early Gentleman scientist, noted for his work in Physics and Chemistry Robert Hooke, FRS (18 July 1635 – 3 March 1703 was an English Natural philosopher and Polymath who played an important role in the [9] Using this pump, Boyle and Hooke noticed a correlation between pressure, temperature, and volume. In time, Boyle's Law was formulated, which states that pressure and volume are inversely proportional. Boyle's law (sometimes referred to as the Boyle-Mariotte law) is one of several Gas laws and a special case of the Ideal gas law. Then, in 1679, based on these concepts, an associate of Boyle's named Denis Papin built a bone digester, which was a closed vessel with a tightly fitting lid that confined steam until a high pressure was generated. Denis Papin ( 22 August 1647 - c 1712 was a French Physicist, Mathematician and Inventor, best known for his pioneering The steam digester (or bone digester, and also known as Papin’s digester) is a high-pressure cooker invented by French physicist Denis Papin in 1679

Later designs implemented a steam release valve that kept the machine from exploding. By watching the valve rhythmically move up and down, Papin conceived of the idea of a piston and a cylinder engine. He did not, however, follow through with his design. Nevertheless, in 1697, based on Papin's designs, engineer Thomas Savery built the first engine. Thomas Savery (c 1650 - 1715 was an English Inventor, born at Shilstone a Manor house near Modbury, Devon, England. Although these early engines were crude and inefficient, they attracted the attention of the leading scientists of the time. One such scientist was Sadi Carnot, the "father of thermodynamics", who in 1824 published Reflections on the Motive Power of Fire, a discourse on heat, power, and engine efficiency. Nicolas Léonard Sadi Carnot (1 June 1796 &ndash 24 August 1832 was a French Physicist and Military engineer who in his 1824 Reflections In the History of thermodynamics, Reflections on the Motive Power of Fire and on Machines Fitted to Develop that Power (French title Réflexions sur la puissance The paper outlined the basic energetic relations between the Carnot engine, the Carnot cycle, and Motive power. A Carnot heat engine is a hypothetical engine that operates on the reversible Carnot cycle. The Carnot cycle is a particular Thermodynamic cycle, modeled on the hypothetical Carnot heat engine, proposed by Nicolas Léonard Sadi Carnot in 1824 and In Thermodynamics, motive power is an agency as Water or Steam, used to impart motion. This marks the start of thermodynamics as a modern science. [2]

The term thermodynamics was coined by James Joule in 1858 to designate the science of relations between heat and power. James Prescott Joule FRS (ˈdʒuːl December 24, 1818 &ndash October 11, 1889) was an English Physicist In Physics, heat, symbolized by Q, is Energy transferred from one body or system to another due to a difference in Temperature In Physics, power (symbol P) is the rate at which work is performed or energy is transmitted or the amount of energy required or expended for [2] By 1849, "thermo-dynamics", as a functional term, was used in William Thomson's paper An Account of Carnot's Theory of the Motive Power of Heat. Year 1849 ( MDCCCXLIX) was a Common year starting on Monday (link will display the full calendar of the Gregorian calendar (or a Common William Thomson 1st Baron Kelvin (or Lord Kelvin) OM, GCVO, PC, PRS, FRSE, (26 June 1824 &ndash 17 December 1907 [10] The first thermodynamic textbook was written in 1859 by William Rankine, originally trained as a physicist and a civil and mechanical engineering professor at the University of Glasgow. Year 1859 ( MDCCCLIX) was a Common year starting on Saturday (link will display the full calendar of the Gregorian calendar (or a Common William John Macquorn Rankine FRS ( July 5, 1820 &ndash December 24, 1872) was a Scottish engineer and The University of Glasgow (Oilthigh Ghlaschu was founded in 1451 in Glasgow, Scotland and along with its contemporary institutions the University of St Andrews [11]

## The laws of thermodynamics

In thermodynamics, there are four laws of very general validity, and as such they do not depend on the details of the interactions or the systems being studied. The laws of thermodynamics, in principle describe the specifics for the transport of Heat and work in Thermodynamic processes. Hence, they can be applied to systems about which one knows nothing other than the balance of energy and matter transfer. Examples of this include Einstein's prediction of spontaneous emission around the turn of the 20th century and current research into the thermodynamics of black holes. Albert Einstein ( German: ˈalbɐt ˈaɪ̯nʃtaɪ̯n; English: ˈælbɝt ˈaɪnstaɪn (14 March 1879 – 18 April 1955 was a German -born theoretical Spontaneous emission is the process by which a light source such as an Atom, Molecule, Nanocrystal or nucleus in an Excited state The twentieth century of the Common Era began on A black hole is a theoretical region of space in which the Gravitational field is so powerful that nothing not even Electromagnetic radiation (e

The four laws are:

• Zeroth law of thermodynamics, stating that thermodynamic equilibrium is an equivalence relation. The zeroth law of thermodynamics is a generalized statement about thermal Equilibrium between bodies in contact In Thermodynamics, a thermodynamic system is said to be in thermodynamic equilibrium when it is in thermal equilibrium Mechanical equilibrium, and In Mathematics, an equivalence relation is a Binary relation between two elements of a set which groups them together as being "equivalent"
If two thermodynamic systems are separately in thermal equilibrium with a third, they are also in thermal equilibrium with each other.
The change in the internal energy of a closed thermodynamic system is equal to the sum of the amount of heat energy supplied to the system and the work done on the system. In Thermodynamics, the first law of thermodynamics is an expression of the more universal physical law of the Conservation of energy. In Physics, the law of conservation of energy states that the total amount of Energy in an isolated system remains constant and cannot be created although it may In Thermodynamics, the internal energy of a Thermodynamic system, or a body with well-defined boundaries, denoted by  U, or sometimes  In Thermodynamics, a thermodynamic system, originally called a working substance, is defined as that part of the universe that is under consideration In Physics, heat, symbolized by Q, is Energy transferred from one body or system to another due to a difference in Temperature In Thermodynamics, work is the quantity of Energy transferred from one system to another without an accompanying transfer of Entropy.
The total entropy of any isolated thermodynamic system tends to increase over time, approaching a maximum value. The second law of Thermodynamics is an expression of the universal law of increasing Entropy, stating that the entropy of an Isolated system which In Thermodynamics (a branch of Physics) entropy, symbolized by S, is a measure of the unavailability of a system ’s Energy
As a system asymptotically approaches absolute zero of temperature all processes virtually cease and the entropy of the system asymptotically approaches a minimum value; also stated as: "the entropy of all systems and of all states of a system is zero at absolute zero" or equivalently "it is impossible to reach the absolute zero of temperature by any finite number of processes". The third law of Thermodynamics is a statistical law of nature regarding Entropy and the impossibility of reaching Absolute zero of Temperature Absolute zero is the point at which molecules do not move (relative to the rest of the body more than they are required to by a quantum mechanical effect called Zero-point Temperature is a physical property of a system that underlies the common notions of hot and cold something that is hotter generally has the greater temperature An asymptote of a real-valued function y=f(x is a curve which describes the behavior of f as either x or y goes to infinity
Express the equality of certain relations between flows and forces in thermodynamic systems out of equilibrium, but where a notion of local equilibrium exists. In Thermodynamics, the Onsager reciprocal relations express the equality of certain relations between flows and Forces in Thermodynamic systems In the various subfields of Physics, there exist two common usages of the term flux, both with rigorous mathematical frameworks In Physics, a force is whatever can cause an object with Mass to Accelerate. In Thermodynamics, a thermodynamic system, originally called a working substance, is defined as that part of the universe that is under consideration In Thermodynamics, a thermodynamic system is said to be in thermodynamic equilibrium when it is in thermal equilibrium Mechanical equilibrium, and In Thermodynamics, a thermodynamic system is said to be in thermodynamic equilibrium when it is in thermal equilibrium Mechanical equilibrium, and
See also: Bose–Einstein condensate and negative temperature. A Bose–Einstein condensate (BEC is a State of matter of Bosons confined in an external Potential and cooled to Temperatures very near to In Physics, certain systems can achieve negative temperatures; that is their Thermodynamic temperature can be of a negative quantity

## Thermodynamic potentials

As can be derived from the energy balance equation ( or Burks' equation) on a thermodynamic system there exist energetic quantities called thermodynamic potentials, being the quantitative measure of the stored energy in the system. A thermodynamic potential is a Scalar potential function used to represent the Thermodynamic state of a system. A thermodynamic potential is a Scalar potential function used to represent the Thermodynamic state of a system. The five most well known potentials are:

 Internal energy $U\,$ Helmholtz free energy $A=U-TS\,$ Enthalpy $H=U+PV\,$ Gibbs free energy $G=U+PV-TS\,$ Grand potential $\Phi_{G}=U-TS-\mu N\,$

Other thermodynamic potentials can be obtained through Legendre transformation. In Thermodynamics, the internal energy of a Thermodynamic system, or a body with well-defined boundaries, denoted by  U, or sometimes  In Thermodynamics, the Helmholtz free energy is a Thermodynamic potential which measures the “useful” work obtainable from a closed thermodynamic In Thermodynamics and molecular chemistry, the enthalpy (denoted as H, h, or rarely as χ) is a quotient or description of In Thermodynamics, the Gibbs free energy ( IUPAC recommended name Gibbs energy or Gibbs function) is a Thermodynamic potential which The grand potential is a quantity used in Statistical mechanics, especially for Irreversible processes in Open systems Grand potential is defined by In Mathematics, it is often desirable to express a functional relationship f(x\ as a different function whose argument is the derivative of f   rather Potentials are used to measure energy changes in systems as they evolve from an initial state to a final state. The potential used depends on the constraints of the system, such as constant temperature or pressure. Internal energy is the internal energy of the system, enthalpy is the internal energy of the system plus the energy related to pressure-volume work, and Helmholtz and Gibbs energy are the energies available in a system to do useful work when the temperature and volume or the pressure and temperature are fixed, respectively.

## Classical thermodynamics

Classical thermodynamics is the original early 1800s variation of thermodynamics concerned with thermodynamic states, and properties as energy, work, and heat, and with the laws of thermodynamics, all lacking an atomic interpretation. Classical thermodynamics is a branch of Physics developed in the nineteenth century by Sadi Carnot (1824 Emile Clapeyron (1834 Rudolf Clausius In precursory form, classical thermodynamics derives from chemist Robert Boyle’s 1662 postulate that the pressure P of a given quantity of gas varies inversely as its volume V at constant temperature; i. Robert Boyle was a Natural philosopher, chemist physicist inventor and early Gentleman scientist, noted for his work in Physics and Chemistry e. in equation form: PV = k, a constant. From here, a semblance of a thermo-science began to develop with the construction of the first successful atmospheric steam engines in England by Thomas Savery in 1697 and Thomas Newcomen in 1712. Thomas Savery (c 1650 - 1715 was an English Inventor, born at Shilstone a Manor house near Modbury, Devon, England. Thomas Newcomen (born shortly before 24 February 1664; died 5 August 1729) was an Ironmonger by trade and a Baptist Year 1712 ( MDCCXII) was a Leap year starting on Friday (link will display the full calendar of the Gregorian calendar (or a Leap The first and second laws of thermodynamics emerged simultaneously in the 1850s, primarily out of the works of William Rankine, Rudolf Clausius, and William Thomson (Lord Kelvin). William John Macquorn Rankine FRS ( July 5, 1820 &ndash December 24, 1872) was a Scottish engineer and Rudolf Julius Emanuel Clausius (Born Rudolf Gottlieb, January 2, 1822 &ndash August 24, 1888) was a German Physicist William Thomson 1st Baron Kelvin (or Lord Kelvin) OM, GCVO, PC, PRS, FRSE, (26 June 1824 &ndash 17 December 1907

## Statistical thermodynamics

With the development of atomic and molecular theories in the late 1800s and early 1900s, thermodynamics was given a molecular interpretation. In Thermodynamics, statistical thermodynamics is the study of the microscopic behaviors of Thermodynamic systems using Probability theory. This field is called statistical thermodynamics, which can be thought of as a bridge between macroscopic and microscopic properties of systems. Essentially, statistical thermodynamics is an approach to thermodynamics situated upon statistical mechanics, which focuses on the derivation of macroscopic results from first principles. Statistical mechanics is the application of Probability theory, which includes mathematical tools for dealing with large populations to the field of Mechanics It can be opposed to its historical predecessor phenomenological thermodynamics, which gives scientific descriptions of phenomena with avoidance of microscopic details. Phenomenological thermodynamics is a branch of Thermodynamics concerned with the study and analysis of actual phenomena with avoidance of full interpretation explanation and The statistical approach is to derive all macroscopic properties (temperature, volume, pressure, energy, entropy, etc. ) from the properties of moving constituent particles and the interactions between them (including quantum phenomena). It was found to be very successful and thus is commonly used.

## Chemical thermodynamics

Chemical thermodynamics is the study of the interrelation of heat with chemical reactions or with a physical change of state within the confines of the laws of thermodynamics. In Thermodynamics, chemical thermodynamics is the mathematical study of the interrelation of Heat and work with Chemical reactions or with a In Physics, heat, symbolized by Q, is Energy transferred from one body or system to another due to a difference in Temperature A chemical reaction is a process that always results in the interconversion of Chemical substances The substance or substances initially involved in a chemical reaction are called A thermodynamic state is the macroscopic condition of a Thermodynamic system as described by its particular thermodynamic parameters. The laws of thermodynamics, in principle describe the specifics for the transport of Heat and work in Thermodynamic processes. During the years 1873-76 the American mathematical physicist Josiah Willard Gibbs published a series of three papers, the most famous being On the Equilibrium of Heterogeneous Substances, in which he showed how thermodynamic processes could be graphically analyzed, by studying the energy, entropy, volume, temperature and pressure of the thermodynamic system, in such a manner to determine if a process would occur spontaneously. Josiah Willard Gibbs ( February 11, 1839 &ndash April 28, 1903) was an American theoretical Physicist, Chemist In the History of thermodynamics, On the Equilibrium of Heterogeneous Substances is a 300-page paper written by American mathematical-engineer Willard Gibbs A thermodynamic process may be defined as the energetic evolution of a Thermodynamic system proceeding from an initial state to a final state In Physics and other Sciences energy (from the Greek grc ἐνέργεια - Energeia, "activity operation" from grc ἐνεργός In Thermodynamics (a branch of Physics) entropy, symbolized by S, is a measure of the unavailability of a system ’s Energy The volume of any solid plasma vacuum or theoretical object is how much three- Dimensional space it occupies often quantified numerically Temperature is a physical property of a system that underlies the common notions of hot and cold something that is hotter generally has the greater temperature Pressure (symbol 'p' is the force per unit Area applied to an object in a direction perpendicular to the surface In Thermodynamics, a thermodynamic system, originally called a working substance, is defined as that part of the universe that is under consideration [12] During the early 20th century, chemists such as Gilbert N. Lewis, Merle Randall, and E. A. Guggenheim began to apply the mathematical methods of Gibbs to the analysis of chemical processes. Gilbert Newton Lewis ( October 23, 1875 - March 23, 1946) was a famous American physical chemist known for the discovery Merle Randall (1888-1950 was an American Physical chemist famous for his work over the period of 25 years in measuring free energy calculations of compounds with Edward Armand Guggenheim (1901 - 1970 was an English Thermodynamicist and professor of chemistry at the University of Reading, noted for his 1933 publication of the [13]

## Thermodynamic systems

Main article: Thermodynamic system

An important concept in thermodynamics is the “system”. In Thermodynamics, a thermodynamic system, originally called a working substance, is defined as that part of the universe that is under consideration Everything in the universe except the system is known as surroundings. A system is the region of the universe under study. A system is separated from the remainder of the universe by a boundary which may be imaginary or not, but which by convention delimits a finite volume. In Thermodynamics, a boundary is a real or imaginary volumetric demarcation region drawn around a Thermodynamic system across which quantities such as Heat The possible exchanges of work, heat, or matter between the system and the surroundings take place across this boundary. In Thermodynamics, work is the quantity of Energy transferred from one system to another without an accompanying transfer of Entropy. In Physics, heat, symbolized by Q, is Energy transferred from one body or system to another due to a difference in Temperature Matter is commonly defined as being anything that has mass and that takes up space. Boundaries are of four types: fixed, moveable, real, and imaginary.

Basically, the “boundary” is simply an imaginary dotted line drawn around a volume of something when there is going to be a change in the internal energy of that something. In Thermodynamics, the internal energy of a Thermodynamic system, or a body with well-defined boundaries, denoted by  U, or sometimes  Anything that passes across the boundary that effects a change in the internal energy of the something needs to be accounted for in the energy balance equation. That something can be the volumetric region surrounding a single atom resonating energy, such as Max Planck defined in 1900; it can be a body of steam or air in a steam engine, such as Sadi Carnot defined in 1824; it can be the body of a tropical cyclone, such as Kerry Emanuel theorized in 1986 in the field of atmospheric thermodynamics; it could also be just one nuclide (i. A steam engine is a Heat engine that performs Mechanical work using Steam as its Working fluid. Nicolas Léonard Sadi Carnot (1 June 1796 &ndash 24 August 1832 was a French Physicist and Military engineer who in his 1824 Reflections A tropical cyclone is a storm system characterized by a low pressure center and numerous Thunderstorms that produce strong winds and Flooding Kerry Emanuel is an American professor of Meteorology currently working at the Massachusetts Institute of Technology in Boston In the Physical sciences atmospheric thermodynamics is the study of Heat and Energy transformations in the earth’s atmospheric system A nuclide (from lat nucleus is a species of Atom characterized by the constitution of its nucleus and hence by the number of Protons, the number of e. a system of quarks) as some are theorizing presently in quantum thermodynamics. In Physics, a quark (kwɔrk kwɑːk or kwɑːrk is a type of Subatomic particle. In the physical sciences quantum thermodynamics is the study of Heat and work dynamics in quantum systems

For an engine, a fixed boundary means the piston is locked at its position; as such, a constant volume process occurs. In that same engine, a moveable boundary allows the piston to move in and out. For closed systems, boundaries are real while for open system boundaries are often imaginary. There are five dominant classes of systems:

1. Isolated Systems – matter and energy may not cross the boundary
2. Adiabatic Systems – heat must not cross the boundary
3. Diathermic Systems - heat may cross boundary
4. Closed Systems – matter may not cross the boundary
5. Open Systems – heat, work, and matter may cross the boundary (often called a control volume in this case)

As time passes in an isolated system, internal differences in the system tend to even out and pressures and temperatures tend to equalize, as do density differences. In Fluid mechanics and Thermodynamics, a control volume is a mathematical abstraction employed in the process of creating Mathematical models A system in which all equalizing processes have gone practically to completion, is considered to be in a state of thermodynamic equilibrium. A thermodynamic state is the macroscopic condition of a Thermodynamic system as described by its particular thermodynamic parameters. In Thermodynamics, a thermodynamic system is said to be in thermodynamic equilibrium when it is in thermal equilibrium Mechanical equilibrium, and

In thermodynamic equilibrium, a system's properties are, by definition, unchanging in time. Systems in equilibrium are much simpler and easier to understand than systems which are not in equilibrium. Often, when analysing a thermodynamic process, it can be assumed that each intermediate state in the process is at equilibrium. This will also considerably simplify the situation. Thermodynamic processes which develop so slowly as to allow each intermediate step to be an equilibrium state are said to be reversible processes. For articles on other forms of reversibility including reversibility of microscopic dynamics see Reversibility (disambiguation.

## Thermodynamic parameters

The central concept of thermodynamics is that of energy, the ability to do work. In Thermodynamics, the Internal energy of a system is expressed in terms of pairs of conjugate variables such as temperature/entropy or pressure/volume In Physics and other Sciences energy (from the Greek grc ἐνέργεια - Energeia, "activity operation" from grc ἐνεργός As stipulated by the first law, the total energy of the system and its surroundings is conserved. In Thermodynamics, the first law of thermodynamics is an expression of the more universal physical law of the Conservation of energy. It may be transferred into a body by heating, compression, or addition of matter, and extracted from a body either by cooling, expansion, or extraction of matter. For comparison, in mechanics, energy transfer results from a force which causes displacement, the product of the two being the amount of energy transferred. Mechanics ( Greek) is the branch of Physics concerned with the behaviour of physical bodies when subjected to Forces or displacements In a similar way, thermodynamic systems can be thought of as transferring energy as the result of a generalized force causing a generalized displacement, with the product of the two being the amount of energy transferred. These thermodynamic force-displacement pairs are known as conjugate variables. In Thermodynamics, the Internal energy of a system is expressed in terms of pairs of conjugate variables such as temperature/entropy or pressure/volume The most common conjugate thermodynamic variables are pressure-volume (mechanical parameters), temperature-entropy (thermal parameters), and chemical potential-particle number (material parameters).

## Thermodynamic instruments

There are two types of thermodynamic instruments, the meter and the reservoir. A thermodynamic instrument is any device which facilitates the quantitative measurement of Thermodynamic systems. A thermodynamic meter is any device which measures any parameter of a thermodynamic system. In Thermodynamics, a thermodynamic system, originally called a working substance, is defined as that part of the universe that is under consideration In some cases, the thermodynamic parameter is actually defined in terms of an idealized measuring instrument. For example, the zeroth law states that if two bodies are in thermal equilibrium with a third body, they are also in thermal equilibrium with each other. The zeroth law of thermodynamics is a generalized statement about thermal Equilibrium between bodies in contact This principle, as noted by James Maxwell in 1872, asserts that it is possible to measure temperature. James Clerk Maxwell (13 June 1831 &ndash 5 November 1879 was a Scottish mathematician and theoretical physicist. An idealized thermometer is a sample of an ideal gas at constant pressure. The thermometer is a device that measures Temperature or Temperature gradient using a variety of different principles it comes from the Greek roots From the ideal gas law PV=nRT, the volume of such a sample can be used as an indicator of temperature; in this manner it defines temperature. The ideal gas law is the Equation of state of a hypothetical Ideal gas, first stated by Benoît Paul Émile Clapeyron in 1834 Although pressure is defined mechanically, a pressure-measuring device, called a barometer may also be constructed from a sample of an ideal gas held at a constant temperature. History The first barometer is thought to have been built unintentionally by Gasparo Berti, sometime between 1640 and 1643 A calorimeter is a device which is used to measure and define the internal energy of a system. A calorimeter is a device used for Calorimetry, the Science of measuring the heat of Chemical reactions or Physical changes as well as Heat

A thermodynamic reservoir is a system which is so large that it does not appreciably alter its state parameters when brought into contact with the test system. It is used to impose a particular value of a state parameter upon the system. For example, a pressure reservoir is a system at a particular pressure, which imposes that pressure upon any test system that it is mechanically connected to. The earth's atmosphere is often used as a pressure reservoir.

It is important that these two types of instruments are distinct. A meter does not perform its task accurately if it behaves like a reservoir of the state variable it is trying to measure. If, for example, a thermometer were to act as a temperature reservoir it would alter the temperature of the system being measured, and the reading would be incorrect. Ideal meters have no effect on the state variables of the system they are measuring.

## Thermodynamic states

Main article: Thermodynamic state

When a system is at equilibrium under a given set of conditions, it is said to be in a definite state. A thermodynamic state is the macroscopic condition of a Thermodynamic system as described by its particular thermodynamic parameters. The state of the system can be described by a number of intensive variables and extensive variables. In the Physical sciences an intensive property (also called a bulk property) is a Physical property of a system that does not depend on the In the Physical sciences an intensive property (also called a bulk property) is a Physical property of a system that does not depend on the The properties of the system can be described by an equation of state which specifies the relationship between these variables. In Physics and Thermodynamics, an equation of state is a relation between state variables More specifically an equation of state is a thermodynamic State may be thought of as the instantaneous quantitative description of a system with a set number of variables held constant

## Thermodynamic processes

A thermodynamic process may be defined as the energetic evolution of a thermodynamic system proceeding from an initial state to a final state. A thermodynamic process may be defined as the energetic evolution of a Thermodynamic system proceeding from an initial state to a final state Typically, each thermodynamic process is distinguished from other processes, in energetic character, according to what parameters, as temperature, pressure, or volume, etc. , are held fixed. Furthermore, it is useful to group these processes into pairs, in which each variable held constant is one member of a conjugate pair. In Thermodynamics, the Internal energy of a system is expressed in terms of pairs of conjugate variables such as temperature/entropy or pressure/volume The seven most common thermodynamic processes are shown below:

1. An isobaric process occurs at constant pressure. An isobaric process is a Thermodynamic process in which the pressure stays constant \Delta p = 0 The term derives from the Greek isos "equal"
2. An isochoric process, or isometric/isovolumetric process, occurs at constant volume. An isochoric process, also called an isovolumetric process, is a process during which volume remains constant
3. An isothermal process occurs at a constant temperature. An isothermal process is a Thermodynamic process in which the Temperature of the System stays Constant: &Delta T = 0
5. An isentropic process (reversible adiabatic process) occurs at a constant entropy. In Thermodynamics, an isentropic process ( iso = "equal" (Greek Entropy = "disorder" is one during which the entropy of the system
6. An isenthalpic process occurs at a constant enthalpy. An isenthalpic process is one that proceeds without any change in Enthalpy, H; or specific enthalpy, h.
7. A steady state process occurs without a change in the internal energy of a system. Steady state is a more general situation than Dynamic equilibrium.

## Quotes & humor

 “ Thermodynamics is a funny subject. Arnold Johannes Wilhelm Sommerfeld (5 December 1868 &ndash 26 April 1951 was a German theoretical Physicist who pioneered developments in atomic The first time you go through it, you don't understand it at all. The second time you go through it, you think you understand it, except for one or two small points. The third time you go through it, you know you don't understand it, but by that time you are so used to it, it doesn't bother you any more. ”
 “ The second law of thermodynamics holds, I think, the supreme position among the laws of Nature. Sir Arthur Stanley Eddington, OM (28 December 1882 – 22 November 1944 was an English Astrophysicist of the early 20th century If someone points out to you that your pet theory of the universe is in disagreement with Maxwell’s equations - then so much the worse for Maxwell’s equations. If it is found to be contradicted by observation, well, these experimentalists do bungle things sometimes. But if your theory is found to be against the second law of thermodynamics I can give you no hope; there is nothing for it but to collapse in deepest humiliation. ”

## References

1. ^ Oxford American Dictionary
2. ^ a b c Perrot, Pierre (1998). In the Physical sciences atmospheric thermodynamics is the study of Heat and Energy transformations in the earth’s atmospheric system Biological thermodynamics is a phrase that is sometimes used to refer to Bioenergetics, the study of Energy transformation in the Biological sciences Biological In Physics, black hole thermodynamics is the area of study that seeks to reconcile the Laws of thermodynamics with the existence of Black hole Event In Thermodynamics, chemical thermodynamics is the mathematical study of the interrelation of Heat and work with Chemical reactions or with a Classical thermodynamics is a branch of Physics developed in the nineteenth century by Sadi Carnot (1824 Emile Clapeyron (1834 Rudolf Clausius Equilibrium Thermodynamics is the systematic study of transformations of matter and energy in systems as they approach equilibrium Non-equilibrium thermodynamics is a branch of Thermodynamics concerned with studying Time -dependent Thermodynamic systems irreversible transformations Phenomenological thermodynamics is a branch of Thermodynamics concerned with the study and analysis of actual phenomena with avoidance of full interpretation explanation and Psychrometrics or psychrometry are terms used to describe the field of engineering concerned with the determination of physical and thermodynamic properties of gas-vapor mixtures In the physical sciences quantum thermodynamics is the study of Heat and work dynamics in quantum systems In Thermodynamics, statistical thermodynamics is the study of the microscopic behaviors of Thermodynamic systems using Probability theory. Thermoeconomics is the name given to a type of heterodox economic theory that attempts to explicitly apply the principles of Thermodynamics to Economics The history of thermodynamics is a fundamental strand in the History of physics, the History of chemistry, and the History of science in general Optics Book of Optics A list of notable textbooks in Statistical mechanics, arranged by date A timeline of events related to Thermodynamics, Statistical mechanics, and Random processes Ancient times c Parmenides of Elea ( Greek:, early 5th century BC was an Ancient Greek Philosopher born in Elea, a Greek city on the southern coast of Calorimetry is the Science of measuring the Heat of Chemical The Debye-Hückel limiting law, named for its developers Peter Debye and Erich Hückel, provides one way to obtain Activity coefficients. Fluid dynamics is the sub-discipline of Fluid mechanics dealing with fluid flow: Fluids ( Liquids and Gases in motion In Mathematics, it is often desirable to express a functional relationship f(x\ as a different function whose argument is the derivative of f   rather In Thermodynamics, the Onsager reciprocal relations express the equality of certain relations between flows and Forces in Thermodynamic systems Gibbs' phase rule, stated by Josiah Willard Gibbs in the 1870s is the fundamental rule on which Phase diagrams are based Autocatalytic reactions are Chemical reactions in which at least one of the products is also a Reactant. In physics quality has several different meanings Thermodynamics The quality of a fluid is the percentage of Mass that is Vapor; i The philosophy of thermal and statistical physics is one of the major subdisciplines of the Philosophy of physics. Statistical mechanics is the application of Probability theory, which includes mathematical tools for dealing with large populations to the field of Mechanics For more elaboration on these equations see Thermodynamic equations. Thermal analysis is a branch of Materials science where the properties of materials are studied as they change with Temperature. For a quick reference table of these equations see Table of thermodynamic equations In Thermodynamics, there are a large number of equations Here is a partial list of thermodynamic properties of Fluids T Temperature *\rho Density Thermodynamic databases contain information about thermodynamic properties for substances the most important being Enthalpy, Entropy, and A to Z of Thermodynamics. Oxford University Press. ISBN 0-19-856552-6.
3. ^ Clark, John, O. E. (2004). The Essential Dictionary of Science. Barnes & Noble Books. ISBN 0-7607-4616-8.
4. ^ Clausius, Rudolf (1850). On the Motive Power of Heat, and on the Laws which can be deduced from it for the Theory of Heat. Poggendorff's Annalen der Physick, LXXIX (Dover Reprint). ISBN 0-486-59065-8.
5. ^ Van Ness, H. C. (1969). Understanding Thermodynamics. Dover Publications, Inc. . ISBN 0-486-63277-6.
6. ^ Dugdale, J. S. (1998). Entropy and its Physical Meaning. Taylor and Francis. ISBN 0-7484-0569-0.
7. ^ Smith, J. M. ; Van Ness, H. C. , Abbott, M. M. (2005). Introduction to Chemical Engineering Thermodynamics. McGraw Hill. ISBN 0-07-310445-0.
8. ^ Haynie, Donald, T. (2001). Biological Thermodynamics. Cambridge University Press. ISBN 0-521-79549-4.
9. ^ Partington, J.R. (1989). James Riddick Partington (June 20 1886 - 1965 was a British Chemist and historian of chemistry A Short History of Chemistry. Dover. ISBN 0-486-65977-1.
10. ^ Kelvin, William T. (1849) "An Account of Carnot's Theory of the Motive Power of Heat - with Numerical Results Deduced from Regnault's Experiments on Steam. " Transactions of the Edinburg Royal Society, XVI. January 2. Scanned Copy
11. ^ Cengel, Yunus A. ; Boles, Michael A. (2005). Thermodynamics - An Engineering Approach. McGraw-Hill. ISBN 0-07-310768-9.
12. ^ Gibbs, Willard (1993). The Scientific Papers of J. Willard Gibbs, Volume One: Thermodynamics. Ox Bow Press. ISBN 0-918024-77-3.
13. ^ Lewis, Gilbert N. ; Randall, Merle (1923). Thermodynamics and the Free Energy of Chemical Substances. McGraw-Hill Book Co. Inc. .