Solids, Liquids & Gases (HL IB Physics)

• The three states of matter are solid, liquid and gas
• The kinetic theory of matter is a model that attempts to explain the properties of the three states of matter
  • In this model, particles are assumed to be small spheres

Water as a solid, liquid, and a gas

Water has three states of matter; solid ice, liquid water and gaseous steam. The difference between each state is the arrangement of the particles

Solids

• Particles in a solid...
  • Are closely packed
  • Are arranged in a fixed pattern (lattice structure)
  • Can only vibrate about their fixed positions
  • Have low energies compared to particles in liquids and gases
  • Therefore, do not have enough energy to overcome the intermolecular forces of attraction holding them together

Molecular arrangement in a solid

In a solid, particles are arranged in a fixed pattern, with no spaces between them, and are only able to vibrate about their fixed positions

• As a result of the arrangement and behaviour of their particles, solids...
  • Have a fixed shape (although some solids can be deformed when forces are applied)
  • Have a fixed volume
  • Are very difficult to compress
  • Have higher densities than liquids and gases

Liquids

• Particles in a liquid...
  
  • Are closely packed
  • Are randomly arranged (i.e. there is no fixed pattern)
  • Can flow past each other
  • Have higher energies than particles in solids, but lower energies than gas particles
  • Therefore, have enough energy to partially overcome the intermolecular forces of attraction holding them together

Molecular arrangement in a liquid

In a liquid, particles are arranged randomly and are able to flow past one another

• As a result of the arrangement and behaviour of their particles, liquids...
  • Do not have a fixed shape and take the shape of the container they are held in
  • Have a fixed volume
  • Are difficult to compress
  • Have lower densities than solids, but higher densities than gases

Gases

• Particles in a gas...
  
  • Are far apart (the average distance between the particles is ∼10 times greater than the distance between the particles in solids and liquids)
  • Are randomly arranged
  • Move around in all directions at a variety of speeds, occasionally colliding with each other and with the walls of the container they are in
  • Are negligible in size compared to the volume occupied by the gas
  • Have higher energies than particles in solids and liquids
  • Therefore, have enough energy to overcome the intermolecular forces of attraction holding them together

Molecular arrangement in a gas

In a gas, particles can move around freely in all directions (shown by the arrows)

• As a result of the arrangement and behaviour of their particles, gases...
  • Do not have a fixed shape and take the shape of the container they are held in
  • Do not have a fixed volume and expand to completely fill the available volume
  • Can be compressed
  • Have the lowest densities (∼1000 times smaller than the densities of solids and liquids)

State of Matter	Solid	Liquid	Gas
Particle arrangement	Fixed pattern (lattice structure)	Random	Random
Space between particles	No space	Some space	Large space
Particle movement	Vibrates around a fixed position	Flows past each other	Moves around at different speeds
Particle energy	Low	Medium	High
Substance shape	Fixed	Not fixed	Not fixed
Substance volume	Fixed	Fixed	Not fixed
Substance density	High	Medium	Low
2D diagram of particle arrangement