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Thermal Physics · Physics

Pressure emerges from countless microscopic collisions.

Use the kinetic picture to connect molecular motion to temperature and to explain why gases exert pressure.

This topic

Kinetic Theory of Gases

Translate between microscopic language (molecules, speeds, collisions) and macroscopic variables (P, V, T).

Model
Microscopic model of gases
The kinetic model treats a gas as many particles moving randomly, colliding with walls and each other.
  • Random motion and large numbers
  • Collisions and momentum transfer
  • What assumptions are being made
Start nano-lesson Assumptions define the model’s reach.
Speeds
Molecular speeds and distributions
Gas molecules do not all move at the same speed; temperature shifts the distribution toward higher speeds.
  • Why “average speed” is not enough
  • Qualitative idea of a speed distribution
  • How heating changes typical speeds
Start nano-lesson Think distribution, not a single value.
Link
Temperature and kinetic energy
Temperature is proportional to average translational kinetic energy per molecule (ideal-gas context).
  • Average kinetic energy increases with T
  • Why Kelvin is the natural scale
  • Conceptual meaning: “hotter” = faster motion
Start nano-lesson Temperature measures typical kinetic energy.
Link
Pressure from molecular motion
Pressure is the result of momentum transfer to container walls from molecular collisions.
  • Why faster molecules increase pressure
  • Why more molecules (higher density) increases pressure
  • Connecting to macroscopic gas laws (conceptual)
Start nano-lesson Pressure is momentum flux.
Practice
Practice & Exercises
Practice translating between micro and macro descriptions and spotting incorrect microscopic claims.
  • Micro–macro interpretation questions
  • Concept checks on speed distributions
  • Temperature vs kinetic energy prompts
  • Pressure-from-collisions reasoning sets
  • Exam-style short explanations
Open practice Explain in words, then in equations.