Kinetic Particle Model of Matter

2026 Syllabus Objectives

By the end of this topic, you should be able to:

States of Matter:

  1. Know the distinguishing properties of solids, liquids and gases
  2. Know the terms for the changes in state between solids, liquids and gases

Particle Model:

  1. Describe the particle structure of solids, liquids and gases in terms of arrangement, separation and motion
  2. Describe the relationship between particle motion and temperature, including absolute zero (−273°C)
  3. Describe the pressure and changes in pressure of a gas in terms of particle motion and collisions
  4. Know that random motion of microscopic particles in suspension is evidence for the kinetic particle model
  5. Describe and explain Brownian motion in terms of random collisions
  6. (Supplement) Know how forces and distances between particles affect properties of matter
  7. (Supplement) Describe gas pressure in terms of forces from particle collisions (force per unit area)
  8. (Supplement) Distinguish between atoms/molecules and microscopic particles

Gases and Absolute Temperature:

  1. Describe qualitatively how temperature and volume changes affect gas pressure
  2. Convert temperatures between kelvin and degrees Celsius
  3. (Supplement) Recall and use pV = constant (Boyle's Law) for a fixed mass of gas at constant temperature

Main Content

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1. States of Matter

All matter exists in one of three states: solid, liquid, or gas. Each state has different properties that depend on how the particles are arranged and how they move.

Solids

  • Shape: Solids have a definite (fixed) shape. They keep their shape no matter what container you put them in.
  • Volume: Solids have a definite (fixed) volume. Their size doesn't change.
  • Flow: Solids cannot flow. The particles are locked in position.
  • Compression: Solids cannot be compressed (squashed). You can't make them smaller by pushing on them.

Example: An ice cube, a metal block, or a piece of wood all keep their shape and size.

Liquids

  • Shape: Liquids have no definite shape. They take the shape of whatever container they're in.
  • Volume: Liquids have a definite (fixed) volume. If you pour 100 mL of water from one container to another, it's still 100 mL.
  • Flow: Liquids can flow. They can be poured and will spread out.
  • Compression: Liquids cannot be compressed. It's very hard to squash them into a smaller space.

Example: Water in a glass takes the shape of the glass, but the amount of water stays the same.

Gases

  • Shape: Gases have no definite shape. They spread out to fill whatever space is available.
  • Volume: Gases have no fixed volume. They expand to fill their container completely.
  • Flow: Gases can flow very easily. Air flows all around us.
  • Compression: Gases are highly compressible. You can squeeze them into a much smaller space (think of pumping air into a bicycle tire).

Example: Air in a balloon fills the entire balloon. If you let the air out, it spreads throughout the room.

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