Molecular physics and thermodynamics

Boyle–Mariotte law , one of the fundamental gas laws, according to which at constant temperature T the volume V of a given mass of gas is inversely proportional to its pressure p, pV=const (Fig.).

Bolometer , ( from the Greek bole — a throw; a ray, and metreo — I measure), a thermal non-selective detector of optical radiation, based on the change in the electrical resistance of a heat-sensitive element when it is …

Boltzmann constant , one of the fundamental physical constants; it is equal to the ratio of the gas constant R to the Avogadro constant N A and is denoted by k; it is named in honour of the Austrian physicist L.

Boltzmann distribution , the statistically equilibrium distribution function over the momenta p and the coordinates r of the particles of an ideal gas whose molecules move according to the laws of classical mechanics, in…

Boltzmann statistics , the statistical method of describing the physical properties of systems that contain a large number of non-interacting particles moving according to the laws of classical mechanics (that is, the pr…

see Brownian motion .

Brownian motion , (Braunian motion), the disorderly motion of small particles suspended in a liquid or a gas, which takes place under the impacts of the molecules of the surrounding medium.

Vacancy , (from the Latin vacans — standing empty, free), the absence of an atom or an ion at a point of a crystal lattice.

A widespread name for the forces of intermolecular interaction.

Variance , (from the Latin varians — changing), the number of degrees of freedom of a thermodynamic system, that is, the number of independent physical variables (parameters of the system) that can be changed (varied) wi…

Gas dynamics - the branch of fluid mechanics that studies the motion of compressible continuous media (gas, plasma) and their interaction with solid bodies.

1) one of the basic gas laws, according to which the volume of a given mass of gas at constant pressure varies linearly with temperature: V t =V 0 (1+α V t), where V 0 and V t are the volumes of the gas at the initial an…

Pressure , a physical quantity characterising the intensity of the normal (perpendicular to the surface) forces with which one body acts on the surface of another (for example, the foundation of a building on the ground,…

1) The pressure of a mixture of chemically non-interacting ideal gases is equal to the sum of the partial pressures.

Liquid thermometer , an instrument for measuring temperature based on the thermal expansion of a liquid.

Ideal gas , a theoretical model of a gas in which the interaction of the gas particles is not taken into account (the mean kinetic energy of the particles is much greater than the energy of their interaction).

Isobar , (from the Greek isos — equal, the same, and baros — weight), a line on a thermodynamic state diagram representing a process that takes place at constant pressure (an isobaric process).

Isobaric process , a process taking place in a physical system at constant external pressure; on a thermodynamic diagram it is represented by an isobar.

(from the Greek isos - equal, the same, and chora - the place occupied), a line on a thermodynamic state diagram that represents an isochoric process.

Kapitza temperature jump , a phenomenon in superfluid liquid helium discovered by P.