- Molecular Motion by Surdendranath is a simple, straightforward model that allows you to adjust volume, number and mass of molecules, and temperature in a container. It offers the option of tracing the path of a single molecule as it undergoes collisions.
https://www.surendranath.org/GPA/Heat/MolMotion/MolMotion.html
Two more simulations in this mold are available in the PhET Collection, both variations on the same underlying structure. The Gases Intro version is a simpler one for introductory classes; the Gas Properties version allows for more complex situations and measurements, including diffusion and energy distributions.
- Gases Intro
https://phet.colorado.edu/en/simulation/gases-intro
- Gas Properties