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Grades 6–9 Beginner About 15 min Version 1 Awaiting review Premium

Particle model: solids, liquids and gases

Everything is made of tiny particles that are always moving. In a solid they are packed in a fixed pattern and only vibrate. In a liquid they are still close together but slide past each other. In a gas they are far apart and move quickly in all directions. Heating gives particles more energy, so they move faster. This model helps explain melting and boiling.

What you will learn

  • Describe the arrangement and movement of particles in solids, liquids and gases.
  • Explain melting, freezing and boiling using the particle model.
  • Recognise that different substances melt and boil at different temperatures.

Before you start

  • Know the names of the three states of matter.

Materials

  • Water
  • Candle wax

Equipment

  • 2 sealed particle viewers (a model, not real equipment)

Procedure

  1. Box A shows water particles and Box B shows wax particles, both at 20 °C.
  2. Cool the water until it freezes, then heat it until it boils. Watch the particles at each step.
  3. Heat the wax until it melts.
  4. Find a temperature at which both substances are liquid.

How this simulation is simplified

  • This is a model. Real particles are far too small to see, and there are far more of them.
  • Particles are drawn as identical circles. Real water and wax particles have different shapes and sizes.
  • The viewers are sealed, so the steam stays inside.
  • Wax melts at about 60 °C here. Real candle wax softens over a range of temperatures.