Solids, Liquids & Gases
Compare and group materials as solids, liquids, or gases based on their observable properties and behaviour
What a learner can do afterwards
- Define solids (fixed shape, hard to compress), liquids (flow, take shape of container), gases (spread out, fill space)
- Sort at least eight everyday materials into solid, liquid, or gas categories
- Explain tricky cases like sand (solid particles) or steam (gas, not visible water droplets)
The lesson
You already know solids, liquids, and gases by name. Today you compare how each one behaves and practice sorting real things into the right group, even some tricky ones.
Mia sorts things on the kitchen table. A rock keeps its shape and feels hard, so it is a solid. Orange juice flows and takes the shape of the glass, so it is a liquid. Air blowing from a fan spreads out and she cannot see it, so it is a gas. She groups the rock, the juice, and the air by watching how each one behaves, not by what it looks like.
Two things trip people up. Sand can be poured, but each tiny grain keeps its own hard shape, so sand is a solid made of many solid pieces. Steam is a gas you cannot see. The white cloud above a boiling kettle is tiny liquid water droplets, not the gas itself.
Solids keep their shape, liquids flow to fit their container, and gases spread out to fully fill it, so sort by how each one behaves, not just how it looks.
Watch it
Where it sits
Where this leads
Jobs that lean on this skill. Follow one to see everything it is built on.
8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.