Changes of State

The three states of matter

• All ordinary matter exists in one of three states at typical temperatures: solid, liquid or gas
• The state determines whether the material has a fixed shape, a fixed volume, and how easily it flows or compresses

Particle behaviour in each state

• Solid
  • Particles are packed tightly in a regular pattern (a lattice)
  • Each particle vibrates about a fixed position; it cannot move past its neighbours
  • The material has a definite shape and a definite volume
• Liquid
  • Particles are still in contact but no longer locked into a lattice; they move freely past one another
  • The material has no definite shape (it flows to fit the bottom of any container) but still has a definite volume
• Gas
  • Particles are far apart with mostly empty space between them
  • Particles move rapidly and randomly in all directions
  • The material has no definite shape and no definite volume; it expands to fill any container it is placed in
  • Gases are easily compressed because the large gaps between particles can be squeezed out