The cylinder contains a fixed amount of ideal air, initially at 20 °C. The model uses PV = nRT, U = nCᵥT, and constant heat capacities with γ = 1.4. Heat flows gently between the walls and a 20 °C room. The piston has mass, atmospheric loading, damping, and finite travel. Mechanical damping dissipates piston motion to the surroundings, outside the gas energy balance.

Compression and expansion change gas temperature through boundary work. The ledger tracks heat and work separately, including cooling by expansion. A torch limiter stops adding heat above 850 K; compression can still raise the temperature. Constant heat capacity is an educational approximation, especially away from room temperature. The dots illustrate molecular motion and density; their number, size and speeds are not to scale. This is a thermodynamics model, not a combustion or engineering safety simulator.

Keyboard: Tab to the piston and use ↑ / ↓ to move it; hold a key to keep the volume constrained, then release. On the torch, ↑ / ↓ adjusts power, Home turns it off, End selects full power, and Space toggles it. On the 3D view, arrow keys orbit and + / − zoom. Pause freezes the experiment; Reset restores its initial state.

Background: NASA: equation of state and specific heats of air.