Time = 0 | Temperature = 0

Click buttons above to add/remove atoms, or to heat up/cool down the atoms. By gradually heating up and cooling down you can see all 3 states of matter, solid, liquid, and gas.

Adjust timestep to change sim speed. Decrease steps per frame if FPS becomes low. Sim will bug out if you make atoms move too fast without decreasing timestep. Adding heavy atoms such as xenon causes helium atoms to move very fast, so you'll need to decrease timestep to prevent bugging out.

This simulator uses the Lennard-Jones potential to approximate the interactions between individual noble gas atoms.

Experiments you can do:

Effects of pressure:
Add 50 helium atoms and heat until temperature hovers around 2. You should have a gas.
Start decreasing box size to 7.5 while cooling to keep temp around 2.
Be sure to cool when needed between box size decreases to prevent atoms from moving too fast, or sim will bug out.
The increased pressure at same temperature has caused gaseous helium to condense into a liquid droplet.
Continue decreasing box size to 4.5.
The extremely high pressure forces the helium to freeze into a solid.

To learn more about this topic, see:
Professor Schroeder's 2D molecular dynamics simulator
Lennard-Jones potential
Molecular dynamics