Topic 3 – Particle Model

• States of matter


  • Solids
  • Liquids
  • Gases
• Solids


  • Strong forces
  • Close together
  • Fixed positions
  • Vibrate
  • Low energy
• Liquids


  • Weak forces
  • Close but random movement
  • Irregular arrangement
  • More energy than solid
• Gases


  • No forces
  • Lots of space between particles
  • Free to move at high speeds
  • Random direction
  • Most energy
• Density


  A measure of compactness
• Measuring density of a solid (regular shape)

  1. Measure mass using balance

  2. Calculate volume (M x W x L)
• Measuring density of a liquid

  1. Get empty measuring cylinder

  2. Place on balance

  3. Pour 10ml (10cm3) of liquid

  4. Record the mass

  5. Calculate density (m/v)

  6. Repeat (1-4) -> average
• Measuring density of a solid (irregular shape)

  1. Measure mass using balance

  2. Fill Eureka can with water

  3. Measure volume of water displaced

  4. H2O displaced = volume of object
• The total energy in a system = sum of (Kinetic + Potential) of all particles
• Potential energy


  Energy in IMF and chemical bonds
• Heating a system


  Particles move faster = ^KE = ^Internal energy of system
• If heated too much


  Particles move fast enough to break bonds = change in state
• Change of state


  Physical change
• Specific Latent Heat (SLH)


  Energy required to change STATE of 1kg of mass
• Freezing/Condensation


  1. Gas/Liquid cools

  2. Particles lose KE

  3. Particles attract and pull together

  4. Form bonds
• Melting/Boiling


  1. Particles gain energy

  2. Overcome attraction of other particles and escape

  3. Break bonds
• SLH


  Energy required to change STATE not temperature
• SHC


  Energy required to change TEMPERATURE not state
• Particles slow down when they collide

  Change in momentum = Force
• Pressure


  Force over a given area (e.g. walls of container)
• What happens to a balloon as it rises up in the sky

  1. Gas particles inside the balloon exert an OUTWARDS pressure

  2. Gas particles in the atmosphere exert an INWARD pressure

  3. As balloon rises, the atmosphere becomes thin/less particles =↓Pressure

  4. Now, OUTWARD > INWARD = OVERALL FORCE (OUT)

  5. Balloon expands causing OUTWARD pressure ↓

  6. When OUTWARD pressure = INWARD pressure -> balloon stops expanding
• Why does a bike pump get hot

  1. Force is used to push plunger down

  2. Applying force requires energy = (energy transfer) = work done

  3. Chemical energy human -> ↑ KE of gas -> ↑ Internal energy of gases

  4. ↑ Internal energy = ↑ Temperature