Kinetic theory of gases

A microscopic model that explains gas properties through the motion and collisions of their constituent particles. It connects particle-level behavior to measurable quantities such as pressure, temperature, and volume.

Maxwell–Boltzmann distribution: A probability distribution describing the speeds of particles in a gas at thermal equilibrium. It shows why gas particles have a range of speeds rather than one shared speed.
Molecular chaos: The assumption that velocities of particles about to collide are statistically independent. It lets collision rates be calculated without tracking correlations between particle histories.
Daniel Bernoulli: An eighteenth-century Swiss mathematician and physicist who explained gas pressure through moving particles. His 1738 kinetic account anticipated the theory’s central explanation of pressure.
Ideal gas: A model gas whose particles have negligible volume and no intermolecular forces except during collisions. It is the limiting case in which the simplest kinetic assumptions apply.
Ideal gas law: The equation of state relating pressure, volume, amount, and absolute temperature for an ideal gas. Kinetic theory derives this macroscopic relation from molecular motion.
Thermal equilibrium: A state in which macroscopic properties remain stable and no net heat flows between systems in contact. Equilibrium gives the stable statistical state described by the theory.
Rudolf Clausius: A German physicist who helped establish thermodynamics and developed the kinetic theory of gases. He formalized molecular motion and introduced the mean free path.
Van der Waals equation: An equation of state that corrects the ideal gas law for molecular size and attraction. Its corrections capture two effects omitted by the simplest kinetic model.
Gas pressure: The force per unit area exerted by gas particles colliding with a surface. Repeated molecular impacts explain how a gas exerts pressure on its container.
Boltzmann constant: The physical constant relating temperature to energy at the scale of individual particles. It converts the gas’s temperature into a characteristic molecular kinetic energy.

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