Kinetic Theory Assumptions

Basic Assumptions

The kinetic theory of gases is based on several fundamental assumptions about the behavior of gas molecules. These assumptions help us understand and predict gas behavior at the molecular level.

Key Assumptions:

  1. Size of Molecules: Gas molecules are infinitesimally small compared to the distances between them. Their total volume is negligible compared to the container volume.
  2. Continuous Motion: Molecules are in constant, random motion, traveling in straight lines until they collide with other molecules or the container walls.
  3. Elastic Collisions: All collisions between molecules and with container walls are perfectly elastic - no loss of kinetic energy.
  4. No Intermolecular Forces: Molecules exert no forces on each other except during collisions (ideal gas assumption).
  5. Temperature Relationship: The average kinetic energy of molecules is directly proportional to absolute temperature.

Mathematical Expression

The average kinetic energy of gas molecules is related to temperature by:

12mv2‾=32kT\frac{1}{2}m\overline{v^2}=\frac{3}{2}kT

where:

  • m = mass of molecule
  • v = velocity
  • k = Boltzmann constant
  • T = absolute temperature