States of matter basics – solids, liquids and gases

PhysicsThermal Physics & GasesAges 13–14

Heat or cool a substance to see its particles rearrange between solid, liquid and gas — every particle really moves under the attractive and repulsive forces between molecules, 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 the container can burst if compressed too hard while hot. Adapted from the "States of Matter: Basics" simulation by PhET Interactive Simulations, University of Colorado Boulder (CC BY 4.0); rewritten.

Lesson: Particle model of matter and states of matter