States of Matter (Oxford AQA IGCSE Combined Science Double Award)

States of Matter

• All matter is made up of very small particles, or atoms

• Kinetic theory is a model that describes the arrangement and movement of particles in a substance

• It can be used to explain

  • The different states of matter e.g. solids, liquids and gases

  • Physical properties e.g. differences in density

Solids

• In a solid the particles:

  • Are closely packed together

  • Vibrate about fixed positions

• The particles in a solid have the least kinetic energy

  • Therefore the particles cannot move very much

  • The particles are bound by the intermolecular forces of attraction

• The density of particles in a solid is high

  • The particles are tightly packed together

• Solids have:

  • A definite shape (they are rigid)

  • A definite volume

Particle arrangement in solids

Liquids

• In a liquid the particles:

  • Are closely packed together

  • Can flow over one another

• The particles in a liquid have more kinetic energy than the particles in a solid

  • Therefore they can flow

  • The particles have enough energy to partially overcome the intermolecular forces of attraction

• The density of particles in a liquid is medium

  • There is generally more space between the particles than in a solid

• Liquids have:

  • No definite shape – they flow and will take the shape of their container

  • A definite volume

Particle arrangement in liquids

Gases

• In a gas the particles:

  • Are far apart

  • Move randomly

• The particles in a gas have a lot of kinetic energy

  • Therefore they are constantly moving and colliding with each other and the container walls

  • The particles have enough energy to overcome the intermolecular forces of attraction

• Gases have:

  • No definite shape – they will take the shape of their container

  • No fixed volume – if placed in an evacuated container they will expand to fill the container

• The density of particles in a gas is low

  • There is a lot of space between the particles

• Gases are highly compressible, this is because:

  • There are large gaps between the particles

  • It is easier to push the particles closer together than in solids or liquids

Particle arrangement in gases

Solids, liquids and gases

Solid, Liquid, Gas Summary Table