Particle Model of Matter

• Solid particles

  • In a fixed position
  • Vibrate very slightly around a fixed position
  • Do not move around
• Liquid particles


  • Move around much more
  • Still touching each other
  • Not in a fixed position
  • Moving about randomly
  • Limited movement within a confined space
• Gas particles


  • Free, smooth and zip around all over the place
• Turning a solid into a liquid

  Adding energy
• Evaporating a liquid into a gas

  Adding energy
• Condensing a gas


  Removing energy
• Freezing a liquid


  Removing energy
• Density


  The amount of mass in a set volume
• Units for density

  Mass in kilograms, volume in meters cubed, density in kilograms per meters cubed
• Specific heat capacity


  How much energy is needed to raise the temperature of 1 kg of a substance by 1 degree
• Units for specific heat capacity

  Energy in joules, mass in kilograms, change in temperature in degrees Celsius, specific heat capacity in joules per kilogram degrees Celsius
• Latent heat


  Energy needed to change a substance from solid to liquid (melting point)
• Units for latent heat

  Energy in joules, mass in kilograms, specific latent heat in joules per kilogram
• For a pure substance, the change from solid to liquid happens instantly at one temperature
• At low temperatures


  More molecules have less energy, fewer have high energy
• At high temperatures


  More molecules have high energy, fewer have low energy
• As molecules evaporate

  The average kinetic energy of the system decreases
• Pressure


  Force exerted by gas particles bumping against the walls of a container
• Units for pressure

  Pressure in Pascals, volume in meters cubed