What Are Solids, Liquids, and Gases?

The spoken lesson

"A solid usually keeps its shape and volume. A liquid keeps its volume but flows and takes the shape of its container. A gas has no fixed shape or volume and expands to fill available space. Scientists use particle models to explain these differences. Particles remain close in solids and liquids but move differently. Gas particles are usually much farther apart. Matter can melt, freeze, evaporate, condense, sublime, or deposit when temperature, pressure, or other conditions change. Water vapour is invisible; the white mist we sometimes see is made mostly of tiny liquid droplets. Matter can change state when conditions change, while the particles remain matter." DESIGN REQUIREMENTS: Use accurate state comparisons and visibly mark particle images as models. Avoid boiling, dry ice, dangerous cold, child-controlled compression, or simplistic "everything pourable is liquid" claims.