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# Gas constant

The gas constant (also known as the molar, universal, or ideal gas constant, denoted by the symbol or) is a physical constant which is featured in many fundamental equations in the physical sciences, such as the ideal gas law and the Nernst equation. [1]

## Amount of substance

Amount of substance is a standards-defined quantity that measures the size of an ensemble of elementary entities, such as atoms, molecules, electrons, and other particles.

## Argon

Argon is a chemical element with symbol Ar and atomic number 18.

## Atomic mass unit

The unified atomic mass unit (symbol: u) or dalton (symbol: Da) is the standard unit that is used for indicating mass on an atomic or molecular scale (atomic mass).

In chemistry and physics, the Avogadro constant (symbols) is the number of constituent particles, usually atoms or molecules, that are contained in the amount of substance given by one mole.

Avogadro's law (sometimes referred to as Avogadro's hypothesis or Avogadro's principle) is an experimental gas law relating volume of a gas to the amount of substance of gas present.

## Bar (unit)

The bar is a metric (but not SI) unit of pressure exactly equal to Pa.

## Boltzmann constant

The Boltzmann constant (kB or k), named after Ludwig Boltzmann, is a physical constant relating energy at the individual particle level with temperature.

## Boyle's law

Boyle's law (sometimes referred to as the Boyle–Mariotte law, or Mariotte's law) is an experimental gas law which describes how the pressure of a gas tends to decrease as the volume of a gas increases.

## Bracket

A bracket is a tall punctuation mark typically used in matched pairs within text, to set apart or interject other text.

## Charles's law

Charles's law (also known as the law of volumes) is an experimental gas law which describes how gases tend to expand when heated.

## Chemist

A chemist is a scientist trained in the study of chemistry.

## Cubic centimetre

A cubic centimetres (or cubic centimeters in US English) (SI unit symbol: cm3; non-SI abbreviations: cc and ccm) is a commonly used unit of volume that extends the derived SI-unit cubic metre, and corresponds to the volume of a cube that measures 1 cm × 1 cm × 1 cm.

## Cubic metre

The cubic metre (in British English and international spelling as used by the International Bureau of Weights and Measures) or cubic meter (in American English) is the SI derived unit of volume.

## Energy

In physics, energy is a property of objects which can be transferred to other objects or converted into different forms, but cannot be created or destroyed.

## Entropy

In thermodynamics, entropy (usual symbol S) is a measure of the number of specific ways in which a thermodynamic system may be arranged, commonly understood as a measure of disorder.

## Erg

The erg is a unit of energy and work equal to 10−7 joules.

## Extrapolation

In mathematics, extrapolation is the process of estimating, beyond the original observation range, the value of a variable on the basis of its relationship with another variable.

## French people

The French (Français) are a nation and ethnic group who are identified with the country of France. This connection may be legal, historical, or cultural. Descending from peoples of Celtic (Gauls) origin, later mixing with Romance (Romans) and Germanic (Franks) origin, and having experienced a high rate of inward migration since the middle of the 19th century, modern French society can be considered a melting pot. France was still a patchwork of local customs and regional differences in the late 19th century, and besides the common speaking of the French language, the definition of some unified French culture is a complex issue. Some French have equated their nationality with citizenship, regardless of ethnicity or country of residence. Successive waves of immigrants during the 19th and 20th centuries were rapidly assimilated into French culture. Seeing itself as an inclusive nation with universal values, France has always valued and strongly advocated assimilation where immigrants were expected to adhere to French traditional values and cultural norms. However, despite the success of such assimilation, the French Government abandoned it in the mid-1980s encouraging immigrants to retain their distinctive cultures and traditions and requiring from them a mere integration. This "integrationist" policy has recently been called into question, for example, following the 2005 French riots in some troubled and impoverished immigrant suburbs. Most French people speak the French language as their mother tongue, but certain languages like Norman, Occitan, Corsican, Basque, French Flemish and Breton remain spoken in certain regions (see Language policy in France). In addition to mainland France, French people and people of French descent can be found internationally, in overseas departments and territories of France such as the French West Indies (French Caribbean), and in foreign countries with significant French-speaking population groups or not, such as Switzerland (French Swiss), the United States (French Americans), Canada (French Canadians), Argentina (French Argentines), Brazil (French Brazilians) or Uruguay (French Uruguayans), and some of them have a French cultural identity.

## Gay–Lussac law

The expression Gay-Lussac's law is used for each of the two relationships named after the French chemist Joseph Louis Gay-Lussac and which concern the properties of gases, though it is more usually applied to his law of combining volumes, the first listed here.

## Heat capacity

Heat capacity or thermal capacity is a measurable physical quantity equal to the ratio of the heat added to (or removed from) an object to the resulting temperature change.

## Heat capacity ratio

In thermal physics and thermodynamics, the heat capacity ratio or adiabatic index or ratio of specific heats or Poisson constant, is the ratio of the heat capacity at constant pressure (C_P) to heat capacity at constant volume (C_V).

## Henri Victor Regnault

Henri Victor Regnault (21 July 1810 – 19 January 1878) was a French chemist and physicist best known for his careful measurements of the thermal properties of gases.

## Ideal gas law

The ideal gas law is the equation of state of a hypothetical ideal gas.

## International Organization for Standardization

The International Organization for Standardization (ISO) is an international standard-setting body composed of representatives from various national standards organizations.

## Joule

The joule, symbol J, is a derived unit of energy in the International System of Units.

## Julius von Mayer

Julius Robert von Mayer (November 25, 1814 – March 20, 1878) was a German physician and physicist and one of the founders of thermodynamics.

## Kelvin

The kelvin is a unit of measure for temperature based upon an absolute scale.

## Mass

In physics, mass is a property of a physical body which determines the strength of its mutual gravitational attraction to other bodies, its resistance to being accelerated by a force, and in the theory of relativity gives the mass–energy content of a system.

## Measurement uncertainty

In metrology, measurement uncertainty is a non-negative parameter characterizing the dispersion of the values attributed to a measured quantity.

## Molar mass

In chemistry, the molar mass M is a physical property defined as the mass of a given substance (chemical element or chemical compound) divided by its amount of substance.

## Mole (unit)

The mole is a unit of measurement for amount of substance.

## Nernst equation

In electrochemistry, the Nernst equation is an equation that relates the reduction potential of a half-cell (or the total voltage, i.e. the electromotive force, of the full cell) at any point in time to the standard electrode potential, temperature, activity, and reaction quotient of the underlying reactions and species used.

## Number density

In physics, astronomy, chemistry, biology and geography, number density (symbol: n or ρN) is an intensive quantity used to describe the degree of concentration of countable objects (particles, molecules, phonons, cells, galaxies, etc.) in physical space: three-dimensional volume number density, two-dimensional area number density, or one-dimensional line number density.

## Pascal (unit)

The pascal (symbol: Pa) is the SI derived unit of pressure, internal pressure, stress, Young's modulus and ultimate tensile strength, defined as one newton per square metre.

## Physical constant

A physical constant is a physical quantity that is generally believed to be both universal in nature and constant in time.

## Pound (force)

The pound or pound-force (symbol: lb, lbf, or lbf) is a unit of force used in some systems of measurement including English Engineering units and the British Gravitational System.

## Pound (mass)

The pound or pound-mass (abbreviations: lb, lbm, lbm, ℔) is a unit of mass used in the imperial, United States customary and other systems of measurement.

## Pressure

Pressure (symbol: p or P) is the force applied perpendicular to the surface of an object per unit area over which that force is distributed.

## Proportionality (mathematics)

In mathematics, two variables are proportional if a change in one is always accompanied by a change in the other, and if the changes are always related by use of a constant multiplier.

## Slug (mass)

The slug is a unit of mass associated with Imperial units and United States customary units.

## Speed of sound

The speed of sound is the distance travelled per unit time by a sound wave propagating through an elastic medium.

## Standard conditions for temperature and pressure

Standard conditions for temperature and pressure are standard sets of conditions for experimental measurements to be established to allow comparisons to be made between different sets of data.

## Standard deviation

In statistics, the standard deviation (SD, also represented by the Greek letter sigma, σ for the population standard deviation or s for the sample standard deviation) is a measure that is used to quantify the amount of variation or dispersion of a set of data values.

## Temperature

A temperature is an objective comparative measure of hot or cold.

## Thermodynamic temperature

Thermodynamic temperature is the absolute measure of temperature and is one of the principal parameters of thermodynamics.

## Torr

The torr (symbol: Torr) is a unit of pressure based on an absolute scale, now defined as exactly of a standard atmosphere.

## U.S. Standard Atmosphere

The U.S. Standard Atmosphere is an atmospheric model of how the pressure, temperature, density, and viscosity of the Earth's atmosphere change over a wide range of altitudes or elevations.

## References

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