Visualizing thermal equilibrium through a simple kinetic simulation

Abstract We present a simple simulation code that models, within a purely mechanical framework, the thermalization process between two ideal gases represented as kinetic billiards. The gases occupy adjacent compartments separated by a mechanically impermeable but ‘diathermic’ wall which mediates virtual exchanges of kinetic energy between particles approaching from opposite sides. The simulation shows the approach to a stationary equilibrium in which both gases attain the same average kinetic energy, thereby providing a microscopic visualization of the concept of thermal equilibrium and of the physical meaning of temperature. The model is fully mechanical, free from thermodynamic assumptions, and runs directly in the GlowScript VPython environment, making it suitable for classroom demonstrations and interactive learning activities at various educational levels.