Practical: Observing the three states of matter
We use simple experiments to compare the three states. When we lift and drop a pencil its shape and volume stay the same – a solid has its own shape and volume and cannot be compressed. When we pour water from a glass into a bowl its shape changes but its volume does not – a liquid has its own volume, no shape of its own, and can be compressed only very slightly. When we blow up a balloon, air fills it and its volume grows – a gas has neither its own shape nor volume and can be compressed. In a solid the particles are packed close, in a liquid there are gaps between them, and in a gas they are very far apart. When heated, ice turns into water and water turns into steam.
Practical work: 1) drop a pencil from 20 cm; 2) pour a glass of water into a bowl; 3) blow up a balloon. Record each in a table. Put an ice cube on a saucer and watch it melt for 10 minutes. Only the teacher works with boiling water: pupils stand at least 1 m from a kettle giving off steam. Safety: pupils do not touch flames or boiling water; use an electric hotplate rather than flammable dry fuel.