States of matter – solids, liquids, gases and phase changes

PhysicsThermal Physics & GasesAges 17–18

Heat, cool, compress and add particles of neon, argon, oxygen or water to watch them rearrange between solid, liquid and gas; every particle really moves under the attractive and repulsive forces between molecules (the Lennard-Jones potential), not a pre-made animation. The States screen heats or cools a sealed container whose lid pops open when it gets too hot; the Phase changes screen lets you compress with a hand-dragged piston, add particles and read the pressure gauge and phase diagram, and the container can burst if compressed too hard while hot; the Interaction potential screen compares the depth of the potential wells of the four substances to explain why their boiling points differ. Adapted from the "States of Matter" simulation by PhET Interactive Simulations, University of Colorado Boulder (CC BY 4.0); rewritten.

Lesson: Kinetic particle model of matter and changes of state