What assumptions define an ideal gas?

Point-like particles, elastic collisions, no long-range forces, and large mean free path so only kinetic energy matters for internal energy in the simplest model.

Ideal Gas Simulator

Bouncing particles in a box. See PV=nRT in action.

About this model

Hard-sphere or particle-in-a-box style model linking microscopic motion to macroscopic variables. Relates kinetic picture to ideal gas law PV = nRT in teaching terms.

Who it's for: Statistical mechanics and thermal physics introductions.

Key terms

ideal gas
pressure
temperature
kinetic theory
PV = nRT

How it works

Hard disks in a 2D box with elastic wall bounces and pairwise collisions. Temperature is identified with mean kinetic energy per particle (k = 1 in model units). For a dilute 2D ideal gas, pressure should track P ≈ NkT/A where A is the area — compare the smoothed wall impulse estimate to NkT/A. Increasing N or T at fixed volume raises pressure; expanding the box lowers it — a qualitative PV ∝ NT demo.

Key equations

⟨KE⟩ = ½m⟨v²⟩ ··· T ≡ ⟨KE⟩/k (2D model)

PV = NkT (ideal gas, area V in 2D)

Frequently asked questions

What assumptions define an ideal gas?: Point-like particles, elastic collisions, no long-range forces, and large mean free path so only kinetic energy matters for internal energy in the simplest model.

Continue with similar topics in this category — or all 46 in Thermodynamics.

View category →

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Ideal Gas Simulator

About this model

How it works

Key equations

Frequently asked questions

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Ideal Gas Simulator

About this model

How it works

Key equations

Frequently asked questions