density  kilogram/metre-cubed (kg/m3)

energy  Joule (J)

mass  kilogram (kg)

pressure  Pascal (Pa)

specific heat capacity  Joule/kilogram x degrees celsius (J/kg℃)

specific latent heat  Joule/kilogram (J/kg)

temperature  degrees celsius (℃)

volume  metre-cubed (m3)

The particle model can be used to explain

  •  The different states of matter (solid, liquid, gas)
  •  Differences in density

The density (measured in kg/m3) of a material is defined by the equation:

density = mass / volume

density = mass / volume

density = 11200 / 12

The density of the iceberg is 933 kg/m3

density = mass / volume

0.18 = mass / 0.014

mass = 0.18 x 0.014

The mass is 0.00252kg

States of Matter


Particle arrangement in a solid

Particles are arranged in a regular pattern

Particles vibrate in a fixed position

Particles have strong forces between them

More dense than liquid & gas

Less energy than liquid & gas


Particle arrangement in a liquid

Particles are arranged in an irregular pattern

Particles move freely

Particles have weak forces between them

More dense than gas, less dense than solid

Less energy than gas, more energy then solid


Particle arrangement in a gas

Particles are in a constant, random motion with a range of speeds and directions

Particles have no forces between them

Less dense than liquid & gas

More energy than liquid & gas

The higher the temperature of the gas higher the average kinetic energy of the molecules of the gas.

When substances change state (melt, freeze, boil, evaporate, condense or sublimate), mass is conserved.

Changes of state are physical changes which differ from chemical changes because the material recovers its original properties if the change is reversed.

  • regular arrangement / pattern of particle in a solid
  • particles are packed close(r) together in a solid
  • particles in a fixed position in a solid
  • heating increases the temperature of the gas
  • temperature is proportional to kinetic energy
  • if kinetic energy increases then the speed increases