kinetic theory of gases

(noun)

The kinetic theory of gases describes a gas as a large number of small particles (atoms or molecules), all of which are in constant, random motion.

Related Terms

Examples of kinetic theory of gases in the following topics:

  • Overview of Temperature and Kinetic Theory

    • The kinetic theory of gases describes a gas as a large number of small particles (atoms and molecules) in constant, random motion.
    • The kinetic theory of gases describes a gas as a large number of small particles (atoms or molecules), all of which are in constant, random motion.
    • Kinetic theory explains macroscopic properties of gases (such as pressure, temperature, and volume) by considering their molecular composition and motion.
    • The kinetic theory of gases uses the model of the ideal gas to relate temperature to the average translational kinetic energy of the molecules in a container of gas in thermodynamic equilibrium .
    • In kinetic theory, the temperature of a classical ideal gas is related to its average kinetic energy per degree of freedom Ek via the equation:

  • Kinetic Molecular Theory and Gas Laws

    • Kinetic Molecular Theory explains the macroscopic properties of gases and can be used to understand and explain the gas laws.
    • The Kinetic Molecular Theory of Gases comes from observations that scientists made about gases to explain their macroscopic properties.
    • Uses the kinetic theory of gases to explain properties of gases (expandability, compressibility, etc. )
    • Reviews kinetic energy and phases of matter, and explains the kinetic-molecular theory of gases.
    • Express the five basic assumptions of the Kinetic Molecular Theory of Gases.

  • Absolute Temperature

    • It is one of the principal parameters of thermodynamics and kinetic theory of gases.
    • At its simplest, "temperature" arises from the kinetic energy of the random motions of matter's particle constituents such as molecules or atoms, as seen in .
    • By using the absolute temperature scale (Kelvin system), which is the most commonly used thermodynamic temperature, we have shown that the average translational kinetic energy (KE) of a particle in a gas has a simple relationship to the temperature:
    • Graph of pressure versus temperature for various gases kept at a constant volume.
    • Real gases do not always behave according to the ideal model under certain conditions, such as high pressure.

  • Atomic Theory of Matter

    • Atomic theory is a scientific theory of the nature of matter which states that matter is composed of discrete units called atoms.
    • Atomic theory is a scientific theory of the nature of matter which states that matter is composed of discrete units called atoms , as opposed to the obsolete notion that matter could be divided into any arbitrarily small quantity.
    • Philosophical proposals regarding atoms have been suggested since the years of the ancient Greeks, but John Dalton was the first to propose a scientific theory of atoms.
    • For this reason, Dalton is considered the originator of modern atomic theory.
    • This effort led to the development of the kinetic theory of gases, where macroscopic properties of gases, such as pressure, temperature, and volume, are explained by considering their molecular composition and motion.

  • Temperature

    • Temperature is directly proportional to the average translational kinetic energy of molecules in an ideal gas.
    • This is a basic and extremely important relationship in the kinetic theory of gases.
    • Note that the average kinetic energy (KE) of a molecule in the gas is:
    • The average translational kinetic energy of a molecule is called thermal energy.
    • It has been found to be valid for gases and reasonably accurate in liquids and solids.

  • Origin of Pressure

    • Pressure is explained by kinetic theory as arising from the force exerted by molecules or atoms impacting on the walls of a container.
    • We can gain a better understanding of pressure (and temperature as well) from the kinetic theory of gases, which assumes that atoms and molecules are in continuous random motion.
    • Pressure is explained by kinetic theory as arising from the force exerted by molecules or atoms impacting on the walls of a container, as illustrated in the figure below.
    • This is a first non-trivial result of the kinetic theory because it relates pressure (a macroscopic property) to the average (translational) kinetic energy per molecule which is a microscopic property.
    • Express the relationship between the pressure and the average kinetic energy of gas molecules in the form of equation

  • Gas Diffusion and Effusion

    • The kinetic theory describes a gas as a large number of submicroscopic particles (atoms or molecules), all of which are in constant rapid motion that has randomness arising from their many collisions with each other and with the walls of the container.
    • Scottish chemist Thomas Graham experimentally determined that the ratio of the rates of effusion for two gases is equal to the square root of the inverse ratio of the gases' molar masses.
    • where M represents the molar mass of the molecules of each of the two gases.
    • (Recall that a result of the Kinetic Theory of Gases is that the temperature, in degrees Kelvin, is directly proportional to the average kinetic energy of the molecules.)
    • Therefore, equating the kinetic energy of molecules 1 and 2, we obtain:

  • Substances that Exist as Gases

    • The Kinetic Theory of Matter provides a basic overview:
    • The temperature of a substance is a measure of the average kinetic energy of the particles.
    • These gases, when grouped together with the monatomic noble gases are called "elemental gases. "
    • Note that unlike solids, gases do not follow a rigidly patterned structure; at a microscopic level, gases are always moving and rearranging themselves.
    • Gases have no definite shape or volume.

  • The Ideal Gas Equation

    • All gases are modeled on the assumptions put forth by the Kinetic Theory of Matter, which assumes that all matter is made up of particles (i.e. atoms or molecules); there are spaces between these particles, and attractive forces become stronger as the particles converge.
    • Each particle has an inherent kinetic energy that is dependent upon temperature only.
    • The ideal gas equation enables us to examine the relationship between the non-constant properties of ideal gases (n, P, V, T) as long as three of these properties remain fixed.
    • The ideal gas equation is a valuable tool that can give a very good approximation of gases at high temperatures and low pressures.
    • There are gases on both sides of a moveable barrier (piston), which stays in the same place (more or less) when you run the model because the gas pressure on the piston is in equilibrium.

  • Internal Energy of an Ideal Gas

    • The kinetic energy is due to the motion of the system's particles (e.g., translations, rotations, vibrations).
    • In this case, the kinetic energy consists only of the translational energy of the individual atoms.
    • The average kinetic energy (KE) of a particle in an ideal gas is given as:
    • (See the Atom on "Temperature" in kinetic theory. ) With N atoms in the gas, its total internal energy U is given as:
    • Note that there are three degrees of freedom in monatomic gases: translation in x, y and z directions.