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68-403: ISO 80000-3 :2019 defines a physical quantity called rotation (or number of revolutions ), dimensionless , whose instantaneous rate of change is called rotational frequency (or rate of rotation ), with units of reciprocal seconds (s). A related but distinct quantity for describing rotation is angular frequency (or angular speed , the magnitude of angular velocity ), for which

136-402: A thermodynamic system is equal to the energy gained as heat, Q {\displaystyle Q} , less the thermodynamic work, W {\displaystyle W} , done by the system on its surroundings. where Δ U {\displaystyle \Delta U} denotes the change in the internal energy of a closed system (for which heat or work through

204-448: A change in the internal energy of the system need to be accounted for in the energy balance equation. The volume contained by the walls can be the 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. The system could also be just one nuclide (i.e. a system of quarks ) as hypothesized in quantum thermodynamics . When

272-417: A correlation between pressure , temperature , and volume . In time, Boyle's Law was formulated, which states that pressure and volume are inversely proportional . Then, in 1679, based on these concepts, an associate of Boyle's named Denis Papin built a steam digester , which was a closed vessel with a tightly fitting lid that confined steam until a high pressure was generated. Later designs implemented

340-430: A few. This article is focused mainly on classical thermodynamics which primarily studies systems in thermodynamic equilibrium . Non-equilibrium thermodynamics is often treated as an extension of the classical treatment, but statistical mechanics has brought many advances to that field. The history of thermodynamics as a scientific discipline generally begins with Otto von Guericke who, in 1650, built and designed

408-521: A large increase in steam engine efficiency. Drawing on all the previous work led Sadi Carnot , the "father of thermodynamics", to publish Reflections on the Motive Power of Fire (1824), a discourse on heat, power, energy and engine efficiency. The book outlined the basic energetic relations between the Carnot engine , the Carnot cycle , and motive power. It marked the start of thermodynamics as

476-403: A looser viewpoint is adopted, and the requirement of thermodynamic equilibrium is dropped, the system can be the body of a tropical cyclone , such as Kerry Emanuel theorized in 1986 in the field of atmospheric thermodynamics , or the event horizon of a black hole . Boundaries are of four types: fixed, movable, real, and imaginary. For example, in an engine, a fixed boundary means the piston

544-662: A modern science. 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 . 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). The foundations of statistical thermodynamics were set out by physicists such as James Clerk Maxwell , Ludwig Boltzmann , Max Planck , Rudolf Clausius and J. Willard Gibbs . Clausius, who first stated

612-424: A physical or notional, but serve to confine the system to a finite volume. Segments of the boundary are often described as walls ; they have respective defined 'permeabilities'. Transfers of energy as work , or as heat , or of matter , between the system and the surroundings, take place through the walls, according to their respective permeabilities. Matter or energy that pass across the boundary so as to effect

680-401: A purely mathematical approach in an axiomatic formulation, a description often referred to as geometrical thermodynamics . A description of any thermodynamic system employs the four laws of thermodynamics that form an axiomatic basis. The first law specifies that energy can be transferred between physical systems as heat , as work , and with transfer of matter. The second law defines

748-441: A set number of variables held constant. A thermodynamic process may be defined as the energetic evolution of a thermodynamic system proceeding from an initial state to a final state. It can be described by process quantities . Typically, each thermodynamic process is distinguished from other processes in energetic character according to what parameters, such as temperature, pressure, or volume, etc., are held fixed; Furthermore, it

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816-439: 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, followed by Thomas Newcomen in 1712. Although these early engines were crude and inefficient, they attracted

884-401: A system on its surrounding requires that the system's internal energy U {\displaystyle U} decrease or be consumed, so that the amount of internal energy lost by that work must be resupplied as heat Q {\displaystyle Q} by an external energy source or as work by an external machine acting on the system (so that U {\displaystyle U}

952-467: A third, they are also in thermal equilibrium with each other. This statement implies that thermal equilibrium is an equivalence relation on the set of thermodynamic systems under consideration. Systems are said to be in equilibrium if the small, random exchanges between them (e.g. Brownian motion ) do not lead to a net change in energy. This law is tacitly assumed in every measurement of temperature. Thus, if one seeks to decide whether two bodies are at

1020-474: A wide variety of topics in science and engineering , such as engines , phase transitions , chemical reactions , transport phenomena , and even black holes . The results of thermodynamics are essential for other fields of physics and for chemistry , chemical engineering , corrosion engineering , aerospace engineering , mechanical engineering , electrical engineering , cell biology , biomedical engineering , materials science , and economics , to name

1088-413: Is a principal property of the thermodynamic state , while heat and work are modes of energy transfer by which a process may change this state. A change of internal energy of a system may be achieved by any combination of heat added or removed and work performed on or by the system. As a function of state , the internal energy does not depend on the manner, or on the path through intermediate steps, by which

1156-399: Is at equilibrium, producing thermodynamic processes which develop so slowly as to allow each intermediate step to be an equilibrium state and are said to be reversible processes . When a system is at equilibrium under a given set of conditions, it is said to be in a definite thermodynamic state . The state of the system can be described by a number of state quantities that do not depend on

1224-501: Is available online. A definition of the decibel , included in the original 2006 publication, was omitted in the 2019 revision, leaving ISO/IEC 80000 without a definition of this unit; a new part of the standard, IEC 80000-15 (Logarithmic and related quantities), is under development. ISO 80000-4:2019 revised ISO 80000-4:2006, which superseded ISO 31-3 . It gives names, symbols, definitions and units for quantities of mechanics. The descriptive text of this part

1292-503: Is available online. ISO 80000-2:2019 revised ISO 80000-2:2009, which superseded ISO 31-11 . It specifies mathematical symbols, explains their meanings, and gives verbal equivalents and applications. The descriptive text of this part is available online. ISO 80000-3:2019 revised ISO 80000-3:2006, which supersedes ISO 31-1 and ISO 31-2 . It gives names, symbols, definitions and units for quantities of space and time. The descriptive text of this part

1360-493: Is available online. ISO 80000-5:2019 revised ISO 80000-5:2007, which superseded ISO 31-4 . It gives names, symbols, definitions and units for quantities of thermodynamics . The descriptive text of this part is available online. IEC 80000-6:2022 revised IEC 80000-6:2008, which superseded ISO 31-5 as well as IEC 60027-1. It gives names, symbols, and definitions for quantities and units of electromagnetism . The descriptive text of this part

1428-542: Is available online. ISO 80000-7:2019 revised ISO 80000-7:2008, which superseded ISO 31-6 . It gives names, symbols, definitions and units for quantities used for light and optical radiation in the wavelength range of approximately 1 nm to 1 mm. The descriptive text of this part is available online. ISO 80000-8:2020 revised ISO 80000-8:2007, which revised ISO 31-7:1992. It gives names, symbols, definitions, and units for quantities of acoustics . The descriptive text of this part

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1496-419: Is available online. It has a foreword, scope introduction, scope, normative references (of which there are none), as well as terms, and definitions. It includes definitions of sound pressure , sound power , and sound exposure , and their corresponding levels : sound pressure level , sound power level , and sound exposure level . It includes definitions of the following quantities: IEC 80000-13:2008

1564-470: Is composed of particles, whose average motions define its properties, and those properties are in turn related to one another through equations of state . Properties can be combined to express internal energy and thermodynamic potentials , which are useful for determining conditions for equilibrium and spontaneous processes . With these tools, thermodynamics can be used to describe how systems respond to changes in their environment. This can be applied to

1632-647: Is determining the spontaneity of a given transformation. Equilibrium thermodynamics is the study of transfers of matter and energy in systems or bodies that, by agencies in their surroundings, can be driven from one state of thermodynamic equilibrium to another. The term 'thermodynamic equilibrium' indicates a state of balance, in which all macroscopic flows 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 distinct parts of

1700-450: Is governed by the four laws of thermodynamics , which convey a quantitative description using measurable macroscopic physical quantities , but may be explained in terms of microscopic constituents by statistical mechanics . Thermodynamics plays a role in a wide variety of topics in science and engineering . Historically, thermodynamics developed out of a desire to increase the efficiency of early steam engines , particularly through

1768-415: Is locked at its position, within which a constant volume process might occur. If the piston is allowed to move that boundary is movable while the cylinder and cylinder head boundaries are fixed. For closed systems, boundaries are real while for open systems boundaries are often imaginary. In the case of a jet engine, a fixed imaginary boundary might be assumed at the intake of the engine, fixed boundaries along

1836-425: Is recovered) to make the system work continuously. For processes that include transfer of matter, a further statement is needed: With due account of the respective fiducial reference states of the systems, when two systems, which may be of different chemical compositions, initially separated only by an impermeable wall, and otherwise isolated, are combined into a new system by the thermodynamic operation of removal of

1904-403: Is said to be in a state of thermodynamic equilibrium . Once in thermodynamic equilibrium, a system's properties are, by definition, unchanging in time. Systems in equilibrium are much simpler and easier to understand than are systems which are not in equilibrium. Often, when analysing a dynamic thermodynamic process, the simplifying assumption is made that each intermediate state in the process

1972-406: Is said to have an angular speed of 2 π  rad/s and a rotation frequency of 1 Hz. The International System of Units (SI) does not recognize rpm as a unit. It defines units of angular frequency and angular velocity as rad s, and units of frequency as Hz , equal to s. ISO 80000-3 ISO/IEC 80000 , Quantities and units , is an international standard describing

2040-420: Is used to model exchanges of energy, work and heat based on the laws of thermodynamics . The qualifier classical reflects the fact that it represents the first level of understanding of the subject as it developed in the 19th century and describes the changes of a system in terms of macroscopic empirical (large scale, and measurable) parameters. A microscopic interpretation of these concepts was later provided by

2108-426: Is −273.15 °C (degrees Celsius), or −459.67 °F (degrees Fahrenheit), or 0 K (kelvin), or 0° R (degrees Rankine ). An important concept in thermodynamics is the thermodynamic system , which is a precisely defined region of the universe under study. Everything in the universe except the system is called the surroundings . A system is separated from the remainder of the universe by a boundary which may be

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2176-476: The Carnot cycle and gave to the theory of heat a truer and sounder basis. 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 applied to heat. The initial application of thermodynamics to mechanical heat engines was quickly extended to

2244-703: The International System of Quantities (ISQ). It was developed and promulgated jointly by the International Organization for Standardization (ISO) and the International Electrotechnical Commission (IEC). It serves as a style guide for using physical quantities and units of measurement , formulas involving them, and their corresponding units, in scientific and educational documents for worldwide use. The ISO/IEC 80000 family of standards

2312-404: The energy , entropy , volume , temperature and pressure of the thermodynamic system in such a manner, one can determine if a process would occur spontaneously. Also Pierre Duhem in the 19th century wrote about chemical thermodynamics. During the early 20th century, chemists such as Gilbert N. Lewis , Merle Randall , and E. A. Guggenheim applied the mathematical methods of Gibbs to

2380-420: The erlang (E), bit (bit), octet (o), byte (B), baud (Bd), shannon (Sh), hartley (Hart), and the natural unit of information (nat). Clause 4 of the standard defines standard binary prefixes used to denote powers of 1024 as 1024 ( kibi- ), 1024 ( mebi- ), 1024 ( gibi- ), 1024 ( tebi- ), 1024 ( pebi- ), 1024 ( exbi- ), 1024 ( zebi- ), and 1024 ( yobi- ). Part 1 of ISO 80000 introduces

2448-435: The erlang (a unit of traffic intensity). The standard includes all SI prefixes as well as the binary prefixes kibi-, mebi-, gibi-, etc., originally introduced by the International Electrotechnical Commission to standardise binary multiples of byte such as mebibyte (MiB), for 1024  bytes, to distinguish them from their decimal counterparts such as megabyte (MB), for precisely 1 million ( 1000 ) bytes. In

2516-549: The International System of Quantities and describes its relationship with the International System of Units (SI). Specifically, its introduction states "The system of quantities, including the relations among the quantities used as the basis of the units of the SI, is named the International System of Quantities , denoted 'ISQ', in all languages." It further clarifies that "ISQ is simply a convenient notation to assign to

2584-414: The SI unit is the radian per second (rad/s). Although they have the same dimensions (reciprocal time) and base unit (s), the hertz (Hz) and radians per second (rad/s) are special names used to express two different but proportional ISQ quantities: frequency and angular frequency, respectively. The conversions between a frequency f and an angular frequency ω are Thus a disc rotating at 60 rpm

2652-415: The analysis of chemical processes. Thermodynamics has an intricate etymology. By a surface-level analysis, the word consists of two parts that can be traced back to Ancient Greek. Firstly, thermo- ("of heat"; used in words such as thermometer ) can be traced back to the root θέρμη therme , meaning "heat". Secondly, the word dynamics ("science of force [or power]") can be traced back to

2720-497: The attention of the leading scientists of the time. The fundamental concepts of heat capacity and latent heat , which were necessary for the development of thermodynamics, were developed by Professor Joseph Black at the University of Glasgow, where James Watt was employed as an instrument maker. Black and Watt performed experiments together, but it was Watt who conceived the idea of the external condenser which resulted in

2788-644: The basic ideas of the second law in his paper "On the Moving Force of Heat", published in 1850, and is 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 being On the Equilibrium of Heterogeneous Substances , in which he showed how thermodynamic processes , including chemical reactions , could be graphically analyzed, by studying

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2856-399: The complete parts for sale. ISO 80000-1:2022 revised ISO 80000-1:2009, which replaced ISO 31-0:1992 and ISO 1000:1992. This document gives general information and definitions concerning quantities, systems of quantities, units, quantity and unit symbols, and coherent unit systems, especially the International System of Quantities (ISQ). The descriptive text of this part

2924-413: The determination of entropy. The entropy determined relative to this point is the absolute entropy. Alternate definitions include "the entropy of all systems and of all states of a system is smallest at absolute zero," or equivalently "it is impossible to reach the absolute zero of temperature by any finite number of processes". Absolute zero, at which all activity would stop if it were possible to achieve,

2992-462: The development of statistical mechanics . Statistical mechanics , also known as statistical thermodynamics, emerged with the development of atomic and molecular theories in the late 19th century and early 20th century, and supplemented classical thermodynamics with an interpretation of the microscopic interactions between individual particles or quantum-mechanical states. This field relates the microscopic properties of individual atoms and molecules to

3060-505: The essentially infinite and continually evolving and expanding system of quantities and equations on which all of modern science and technology rests. ISQ is a shorthand notation for the 'system of quantities on which the SI is based'." The standard includes all SI units but is not limited to only SI units. Units that form part of the standard but not the SI include the units of information storage ( bit and byte ), units of entropy ( shannon , natural unit of information and hartley ), and

3128-452: The existence of a quantity called entropy , that describes the direction, thermodynamically, that a system can evolve and quantifies the state of order of a system and that can be used to quantify the useful work that can be extracted from the system. In thermodynamics, interactions between large ensembles of objects are studied and categorized. Central to this are the concepts of the thermodynamic system and its surroundings . A system

3196-472: The macroscopic, bulk properties of materials that can be observed on the human scale, thereby explaining classical thermodynamics as a natural result of statistics, classical mechanics, and quantum theory at the microscopic level. Chemical thermodynamics is the study of the interrelation of energy with chemical reactions or with a physical change of state within the confines of the laws of thermodynamics . The primary objective of chemical thermodynamics

3264-498: The other laws. The first, second, and third laws had been explicitly stated already, and found common acceptance in the physics community before the importance of the zeroth law for the definition of temperature was realized. As it was impractical to renumber the other laws, it was named the zeroth law . The first law of thermodynamics states: In a process without transfer of matter, the change in internal energy , Δ U {\displaystyle \Delta U} , of

3332-457: The prefixes for binary multiples. The only significant change in IEC ;80000-13 is the addition of explicit definitions for some quantities. Thermodynamics Thermodynamics is the branch of physics that studies heat , work , and temperature and their relation to energy , entropy , and the physical properties of matter and radiation . The behavior of these quantities

3400-399: The process by which the system arrived at its state. They are called intensive variables or extensive variables according to how they change when the size of the system changes. The properties of the system can be described by an equation of state which specifies the relationship between these variables. State may be thought of as the instantaneous quantitative description of a system with

3468-407: The rates of approach to thermodynamic equilibrium, and thermodynamics does not deal with such rates. The many versions of the second law all express the general irreversibility of the transitions involved in systems approaching thermodynamic equilibrium. In macroscopic thermodynamics, the second law is a basic observation applicable to any actual thermodynamic process; in statistical thermodynamics,

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3536-459: The root δύναμις dynamis , meaning "power". In 1849, the adjective thermo-dynamic is used by William Thomson. In 1854, the noun thermo-dynamics is used by Thomson and William Rankine to represent the science of generalized heat engines. Pierre Perrot claims that the term thermodynamics was coined by James Joule in 1858 to designate the science of relations between heat and power, however, Joule never used that term, but used instead

3604-400: The same temperature , it is not necessary to bring them into contact and measure any changes of their observable properties in time. The law provides an empirical definition of temperature, and justification for the construction of practical thermometers. The zeroth law was not initially recognized as a separate law of thermodynamics, as its basis in thermodynamical equilibrium was implied in

3672-494: The scope of currently known macroscopic thermodynamic methods. Thermodynamics is principally based on a set of four laws which are universally valid when applied to systems that fall within the constraints implied by each. In the various theoretical descriptions of thermodynamics these laws may be expressed in seemingly differing forms, but the most prominent formulations are the following. The zeroth law of thermodynamics states: If two systems are each in thermal equilibrium with

3740-443: The second law is postulated to be a consequence of molecular chaos. The third law of thermodynamics states: As the temperature of a system approaches absolute zero, all processes cease and the entropy of the system approaches a minimum value. This law of thermodynamics is a statistical law of nature regarding entropy and the impossibility of reaching absolute zero of temperature. This law provides an absolute reference point for

3808-452: The standard, the application of the binary prefixes is not limited to units of information storage. For example, a frequency 10  octaves above 1 hertz, i.e., 2  Hz (1024 Hz), is 1 kibihertz (1 KiHz). These binary prefixes were standardized first in a 1999 addendum to IEC 60027-2 . The harmonized IEC 80000-13:2008 standard cancels and replaces subclauses 3.8 and 3.9 of IEC 60027-2:2005, which had defined

3876-555: The study of chemical compounds and chemical reactions. Chemical thermodynamics studies the nature of the role of entropy in the process of chemical reactions and has provided the bulk of expansion and knowledge of the field. Other formulations of thermodynamics emerged. Statistical thermodynamics , or statistical mechanics, concerns itself with statistical predictions of the collective motion of particles from their microscopic behavior. In 1909, Constantin Carathéodory presented

3944-407: The surface of the case and a second fixed imaginary boundary across the exhaust nozzle. Generally, thermodynamics distinguishes three classes of systems, defined in terms of what is allowed to cross their boundaries: As time passes in an isolated system, internal differences of pressures, densities, and temperatures tend to even out. A system in which all equalizing processes have gone to completion

4012-486: The system arrived at its state. A traditional version of the second law of thermodynamics states: Heat does not spontaneously flow from a colder body to a hotter body. The second law refers to a system of matter and radiation, initially with inhomogeneities in temperature, pressure, chemical potential, and other intensive properties , that are due to internal 'constraints', or impermeable rigid walls, within it, or to externally imposed forces. The law observes that, when

4080-470: The system boundary are possible, but matter transfer is not possible), Q {\displaystyle Q} denotes the quantity of energy supplied to the system as heat, and W {\displaystyle W} denotes the amount of thermodynamic work done by the system on its surroundings. An equivalent statement is that perpetual motion machines of the first kind are impossible; work W {\displaystyle W} done by

4148-448: The system is isolated from the outside world and from those forces, there is a definite thermodynamic quantity, its entropy , that increases as the constraints are removed, eventually reaching a maximum value at thermodynamic equilibrium, when the inhomogeneities practically vanish. For systems that are initially far from thermodynamic equilibrium, though several have been proposed, there is known no general physical principle that determines

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4216-859: The system. A central aim in equilibrium thermodynamics is: given a system in a well-defined initial equilibrium state, and given its surroundings, and given its constitutive walls, to calculate what will be the final equilibrium state of the system after a specified thermodynamic operation has changed its walls or surroundings. 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 stationary states, and are continuously and discontinuously subject to flux of matter and energy to and from other systems. The thermodynamic study of non-equilibrium systems requires more general concepts than are dealt with by equilibrium thermodynamics. Many natural systems still today remain beyond

4284-462: The term perfect thermo-dynamic engine in reference to Thomson's 1849 phraseology. The study of thermodynamical systems has developed into several related branches, each using a different fundamental model as a theoretical or experimental basis, or applying the principles to varying types of systems. Classical thermodynamics is the description of the states of thermodynamic systems at near-equilibrium, that uses macroscopic, measurable properties. It

4352-427: The wall, then where U 0 denotes the internal energy of the combined system, and U 1 and U 2 denote the internal energies of the respective separated systems. Adapted for thermodynamics, this law is an expression of the principle of conservation of energy , which states that energy can be transformed (changed from one form to another), but cannot be created or destroyed. Internal energy

4420-585: The work of French physicist Sadi Carnot (1824) who believed that engine efficiency was the key that could help France win the Napoleonic Wars . 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 forces acting between contiguous parts of bodies, and the relation of heat to electrical agency." German physicist and mathematician Rudolf Clausius restated Carnot's principle known as

4488-511: The world's first vacuum pump and demonstrated a vacuum using his Magdeburg hemispheres . Guericke was driven to make a vacuum to disprove Aristotle 's long-held supposition that 'nature abhors a vacuum'. Shortly after Guericke, the Anglo-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. Using this pump, Boyle and Hooke noticed

4556-474: Was completed with the publication of the first edition of Part 1 in November 2009. By 2021, ISO/IEC 80000 comprised 13 parts, two of which (parts 6 and 13) were developed by IEC and the remaining 11 were developed by ISO, with a further three parts (15, 16 and, 17) under development. Part 14 was withdrawn. By 2021 the 80000 standard had 13 published parts. A description of each part is available online, with

4624-545: Was reviewed and confirmed in 2022 and published in 2008, and replaced subclauses 3.8 and 3.9 of IEC 60027-2:2005 and IEC 60027-3 . It defines quantities and units used in information science and information technology , and specifies names and symbols for these quantities and units. It has a scope; normative references; names, definitions, and symbols; and prefixes for binary multiples. Quantities defined in this standard are: The standard also includes definitions for units relating to information technology, such as

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