Stop 1 of 12 · The path
Matter — what stuff is
Everything you can weigh and take up room is matter. This stop sorts it: mass, volume, properties, and the three common states.
Bench tool
The weighing tool
Density = mass ÷ volume. Try it:
Density =
Water is 1 g/cm³, aluminium about 2.7, iron about 7.9.
How it works
- Mass tells how much. Weighed in grams. It does not change when you carry it upstairs.
- Volume tells how much room. In cm³ or litres. Same mass, bigger volume means lighter stuff.
- Properties tell which. Density, hardness, melting point. They identify the material, not the lump.
Worked examples
200 g in 50 cm³. 200 ÷ 50 = 4 g/cm³ — about aluminium.
Ice melts. Still water, still H₂O. A change of state, not of substance.
Iron rusts. Red flakes, new substance. That is a chemical change.
Is air matter? Yes — it has mass and takes room. A blown-up ball weighs a little more.
Where it goes wrong
Mass vs weight. Weight pulls; mass stays. In space you are weightless, not massless.
Melting vs dissolving. Ice melts to water. Salt dissolves into water — still there, get it back by evaporating.
Try it at home: sink or stack
Density tower. Layer honey, washing-up liquid, coloured water, and cooking oil in a tall glass, then drop in a grape, a coin, and a bottle cap. They settle in order of density — not weight alone.
For teachers
Learners call every change of state a chemical change — probe by asking whether evaporated salt water leaves salt behind. Quickest check: hand them ice, rust, and dissolved salt and ask which made a new substance.