Who invented the zeroth law of the thermodynamic sample

Thermodynamics - Thermodynamics

Physics of heat, work and temperature

The thermodynamics is a branch of physics that deals with heat, work and temperature and their relationship to energy, radiation and the physical properties of matter. The behavior of these quantities is determined by the four laws of thermodynamics, which convey a quantitative description using measurable macroscopic physical quantities, but can be explained by statistical mechanics through microscopic components. Thermodynamics applies to a variety of topics in science and technology, especially physical chemistry, biochemistry, chemical engineering and mechanical engineering, but also to other complex areas such as meteorology.

Historically, thermodynamics arose out of a desire to increase the efficiency of early steam engines, particularly through the work of the French physicist Nicolas Léonard Sadi Carnot (1824) who believed that engine efficiency was the key that France could help that Winning Napoleonic Wars. The Scottish-Irish physicist Lord Kelvin was the first to formulate a precise definition of thermodynamics in 1854, which states: "Thermodynamics is the subject of the relationship between heat and forces acting between connected body parts and the relationship between heat and electrical action. "

The initial application of thermodynamics to mechanical heat engines quickly expanded to the study of chemical compounds and chemical reactions. Chemical thermodynamics studies the nature of the role entropy plays in the process of chemical reactions and has provided much of the expansion and expertise. Other formulations of thermodynamics emerged. Statistical thermodynamics or statistical mechanics is concerned with statistical predictions of the collective motion of particles from their microscopic behavior. In 1909 Constantin Carathéodory presented a purely mathematical approach in an axiomatic formulation, a description that is often called geometric thermodynamics is called .


A description of a thermodynamic system uses the four laws of thermodynamics, which form an axiomatic basis. The first law states that energy can be exchanged between physical systems as heat and work. The second law defines the existence of a quantity called entropy, which thermodynamically describes the direction in which a system can evolve and quantify the state of order of a system, and which can be used to quantify the useful work that can be extracted from the system .

In thermodynamics, interactions between large ensembles of objects are examined and categorized. The focus is on the concepts of the thermodynamic Systems and his Surroundings . A system consists of particles whose average motions define its properties, and these properties are in turn linked by equations of state. Properties can be combined to express internal energy and thermodynamic potentials, which are useful in determining the conditions for equilibrium and spontaneous processes.

These tools can use thermodynamics to describe how systems react to changes in their environment. This can be applied to a wide variety of topics in science and engineering, such as motors, phase transitions, chemical reactions, transport phenomena, and even black holes. The results of thermodynamics are essential to other areas of physics and to chemistry, chemical engineering, corrosion engineering, aerospace engineering, mechanical engineering, cell biology, biomedical engineering, materials science, and economics, to name a few.

This article mainly focuses on classical thermodynamics, which mainly studies systems in thermodynamic equilibrium. Non-equilibrium thermodynamics is often treated as an extension of classical treatment, but statistical mechanics has made many advances in this area.


The history of thermodynamics as a scientific discipline generally begins with Otto von Guericke, who built and designed the world's first vacuum pump in 1650 and demonstrated a vacuum with his Magdeburg hemispheres. Guericke was driven to create a vacuum to refute Aristotle's long-held belief that "nature abhors a vacuum". Shortly after Guericke, the Anglo-Irish physicist and chemist Robert Boyle learned of Guericke's designs and, in coordination with the English scientist Robert Hooke, built an air pump in 1656. With this pump, Boyle and Hooke found a correlation between pressure, temperature and volume. Over time, Boyle's law was formulated, which states that pressure and volume are inversely proportional. In 1679, based on these concepts, a Boyle collaborator named Denis Papin built a steamer, a closed vessel with a tight-fitting lid that restricted steam until high pressure was created.

Later designs implemented a vapor release valve that kept the machine from exploding. Papin watched the valve move rhythmically up and down and came up with the idea of ​​a piston and a cylinder motor. However, he did not implement his design. Even so, engineer Thomas Savery built the first engine based on Papin's designs in 1697, followed by Thomas Newcomen in 1712. Although these early engines were crude and inefficient, they caught the attention of the leading scientists of the time.

The basic concepts of heat capacity and latent heat 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 conducted experiments together, but it was Watt who came up with the idea of ​​the external condenser, which greatly increased the efficiency of the steam engine. Based on all earlier works, Sadi Carnot, the "father of thermodynamics", published Reflections on the Motive Power of Fire (1824), a discourse on heat, power, energy and engine efficiency. The book outlined the basic energetic relationships between the Carnot engine, the Carnot cycle, and the Driving force . It was the beginning of thermodynamics as a modern science.

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

Between 1873 and 1876, the American mathematical physicist Josiah Willard Gibbs published a series of three papers, the best known of which was the equilibrium of heterogeneous substances in which he showed how thermodynamic processes, including chemical reactions, can be graphically analyzed through studies of the energy, entropy, volume, temperature and pressure of the thermodynamic system in such a way that one can determine whether a process would occur spontaneously. Pierre Duhem also wrote about chemical thermodynamics in the 19th century. During the early 20th century, chemists such as Gilbert N. Lewis, Merle Randall, and EA Guggenheim used Gibbs' mathematical methods to analyze chemical processes.


The etymology of the thermodynamics has a complicated story. It was first used separately as an adjective ( thermodynamically ) and from 1854 to 1868 as a noun written thermodynamics to illustrate the science of generalized heat engines.

The American biophysicist Donald Haynie claims that the thermodynamics 1840 from the Greek root θέρμη therme ( Heat) and δύναμις dynamis ( Kraft) was coined.

Pierre Perrot claims that the term thermodynamics Coined by James Joule in 1858 to denote the science of the relationships between heat and energy. However, Joule never used this term, but used the term instead perfect thermodynamic engine regarding Thomson's language of 1849.

1858 thermo dynamics as a functional term it was used in William Thomson's paper, `` A Report from Carnot's Theory of Motive Power of Heat. ''

Branches of thermodynamics

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

Classical thermodynamics

Classical thermodynamics is the description of the states of thermodynamic systems in near equilibrium, which uses macroscopic, measurable properties. It is used to model the exchange of energy, work and heat based on the laws of thermodynamics. The qualifier classic reflects the fact that it represents the first level of understanding of the subject as it evolved 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 made possible by the development of the statistical mechanics delivered.

Statistical Mechanics

Statistical mechanics, also known as statistical thermodynamics, arose with the development of atomic and molecular theories in the late 19th and early 20th centuries 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 the macroscopic bulk properties of materials that can be observed on a human level, thus explaining classical thermodynamics as a natural result of statistics, classical mechanics and quantum theory on a microscopic level.

Chemical thermodynamics

Chemical thermodynamics is understood to be the investigation of the connection between energy and chemical reactions or with a physical change of state within the limits of the laws of thermodynamics.

Equilibrium thermodynamics

Equilibrium thermodynamics is the study of the transfer of matter and energy in systems or bodies that can be driven from one state of thermodynamic equilibrium to another by agencies in their environment. The term "thermodynamic equilibrium" denotes a state of equilibrium in which all macroscopic flows are zero; In the simplest systems or bodies, their intense properties are homogeneous and their pressures are perpendicular to their limits. In a state of equilibrium there are no unbalanced potentials or driving forces between macroscopically different parts of the system. A central goal of equilibrium thermodynamics is: given a system in a well-defined initial state of equilibrium and given its surroundings and its constitutive walls, to calculate what the final state of equilibrium of the system will look like after a particular 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 naturally occurring systems are not in thermodynamic equilibrium because they are not in stationary states and are continuously and discontinuously exposed to the flow of matter and energy to and from other systems. The thermodynamic study of non-equilibrium systems requires more general concepts than equilibrium thermodynamics. Many natural systems are still outside the scope of the currently known macroscopic thermodynamic methods.

Laws of Thermodynamics

Thermodynamics is mainly based on a set of four laws that are universally valid when applied to systems falling within the limitations implied by each. In the various theoretical descriptions of thermodynamics, these laws can be expressed in seemingly different forms, but the most well-known formulations are as follows.

Zeroth law

The zeroth law of thermodynamics says: If two systems are in thermal equilibrium with a third, they are also in thermal equilibrium with each other.

This statement implies that the thermal equilibrium is an equivalence relationship for the set of considered thermodynamic systems. Systems are considered to be in equilibrium if the small, random exchange between them (e.g. Brownian motion) does not lead to a net change in energy. This law is tacitly accepted in every temperature measurement. So if one wants to decide whether two bodies are at the same temperature, it is not necessary to bring them into contact and measure changes in their observable properties over time. The law provides an empirical definition of temperature and a justification for building practical thermometers.

The zeroth law was not originally recognized as a separate law of thermodynamics because its basis in thermodynamic equilibrium was implied in the other laws. The first, second and third laws were already explicitly stated and found wide acceptance in physics before the importance of the zeroth law for the definition of temperature was recognized. Since it was impractical to renumber the other laws, it was called called zeroth law .

First law

The first law of thermodynamics determines: In a process without the transfer of matter, the change in internal energy, Δ U , in a thermodynamic system, the energy is obtained as heat, Q , less thermodynamic work, W. , through the system to its environment.


For processes that involve the transfer of matter, a further statement is required: With due consideration of the respective reference reference states of the systems, if two systems, which can have different chemical compositions, are initially only separated by an impermeable wall and are otherwise isolated, they are then combined into a new system by the thermodynamic process of removing the wall


in which U 0 denotes the internal energy of the combined system and U 1 and U 2 denote the inner energies of the respective separate systems.

Adapted to thermodynamics, this law expresses the principle of conservation of energy, which states that energy can be converted (changed from one form to another), but cannot be created or destroyed.

Internal energy is a major property of the thermodynamic state, while heat and work are modes of energy transfer through which a process can change this state. A change in the internal energy of a system can be achieved by any combination of heat supply or removal and work on or through the system. Depending on the state, the internal energy does not depend on the way or the way through intermediate steps through which the system came to its state.

Second law

A traditional version of the second law of thermodynamics states: Heat does not spontaneously flow from a colder body to a hotter one.

The second law relates to a system of matter and radiation that initially exhibits inhomogeneities in terms of temperature, pressure, chemical potential and other intense properties due to internal "constraints" or impermeable rigid walls within it or to externally imposed forces are . The law states that when the system is isolated from the outside world and from these forces, there is a certain thermodynamic quantity, the entropy of which increases when the restrictions are lifted and eventually reaches a maximum value in thermodynamic equilibrium when the Inhomogeneities practically disappear. For systems that are initially far from thermodynamic equilibrium, although several have been proposed, no general physical principle is known that determines rates of approach to thermodynamic equilibrium, and thermodynamics does not deal with such rates. The many versions of the second law all express the irreversibility of such an approach to thermodynamic equilibrium.

In macroscopic thermodynamics, the second law is a fundamental observation applicable to any actual thermodynamic process. In statistical thermodynamics it is postulated that the second law is a consequence of molecular chaos.

Third law

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

This law of thermodynamics is a statistical law of nature related to entropy and the impossibility of reaching absolute zero of temperature. This law provides an absolute reference point for determining entropy. The entropy determined relative to this point is the absolute entropy. Alternative definitions include "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 a finite number of processes".

The absolute zero at which all activity would stop if it were possible is -273.15 ° C (degrees Celsius) or -459.67 ° F (degrees Fahrenheit) or 0 K (Kelvin) or 0 ° R (degrees Rankine)).

System models

A diagram of a generic thermodynamic system

An important concept in thermodynamics is the thermodynamic system, a well-defined region of the universe under study. Everything in the universe except the system becomes the Called environment . A system is from the rest of the universe by one Border separated, which can be physical or fictional, but serves to restrict the system to a finite volume. Segments of the border are often called Walls described ; They each have defined "permeabilities". The transfer of energy as work or as heat or matter between the system and the environment takes place according to their respective permeability through the walls.

Matter or energy that crosses the limit to cause a change in the internal energy of the system must be taken into account in the energy balance equation. The volume contained by the walls can be the area surrounding a single atomic resonance energy, such as Max Planck, who was defined in 1900; It can be a body of steam or air in a steam engine, such as Sadi Carnot, which was defined in 1824. The system could also be just a nuclide (ie a system of quarks), as assumed in quantum thermodynamics. If a looser point of view is taken and the need for thermodynamic equilibrium is eliminated, the system can be the body of a tropical cyclone, as Kerry Emanuel theorized in 1986 in the field of atmospheric thermodynamics, or the event horizon of a black hole.

There are four types of boundaries: fixed, movable, real and imaginary. For example, in an engine, a fixed limit means that the piston is locked in position within which a constant volume process can occur. If the piston is allowed to move, this limit is movable while the cylinder and cylinder head limits are fixed. In closed systems, boundaries are real, while in open systems, boundaries are often imaginary. In the case of a jet engine, a fixed imaginary boundary could be assumed at the inlet of the engine, fixed boundaries along the surface of the casing, and a second fixed imaginary boundary above the exhaust nozzle.

In general, thermodynamics distinguishes three classes of systems, which are defined in terms of what is allowed to exceed its limits:

Over time in an isolated system, internal differences in pressure, density, and temperature cancel each other out. A system in which all equilibrium processes have been said to have taken place is in its state of thermodynamic equilibrium.

In thermodynamic equilibrium, the properties of a system remain unchanged over time by definition. Systems in equilibrium are much simpler and easier to understand than systems that are not in equilibrium. When analyzing a dynamic thermodynamic process, the simplifying assumption is often made that every intermediate state in the process is in equilibrium, creating thermodynamic processes that develop so slowly that each intermediate step can be a state of equilibrium and as