3 - Particle Model of Matter

• Solids particles :

  • Close together, arranged In a regular pattern, particles vibrate but do not move from place to place 
  • high density = particles are packed close together so they have more mass for their volume 
• Liquids Particles : 

  • Close together, not arranged in a regular pattern, can move around each other 
  • High density= particles are close together, they have lots of mas  for their volume 
• Gas particles:

  • Far apart, not arranged in any pattern, move very rapidly 
  • Low density= particles are far apart, so they have a smaller mass for their volume 
• density: the mass for for a give volume 

  Exceptions: polystyrene is a solid by has a low density

  • its structure is open and full of air spaces so it has a small mass for its volume. 
•  density = mass/volume

  
• Required Practical: Density

  Regular: 

  • mass: use a balance, volume: ruler to measure length the sides  (length x width x height)

  Irregular: 

  1. Use balance to find mass
  2. Fill a eurekan can with water. Place object into the water, this will cause the water to be displaced and flow out the can through the spout 
  3. Measure the volume of the water displaced. This is the volume is the same as the volume of the object 
  4. Calculate density: density= mass / volume 
• All particles have energy, they also have potential energy (intermolecular forces and chemical bonds) 

  Internal energy is the energy stored in a system by particles, 

  • the total kinetic energy and potential energy of all the particles that make up a system
• Melting: solid to liquid, increase in internal energy

  Boiling: liquid to gas, increase in internal energy 

  Condensation: gas to liquid, reduce internal energy

  Freezing: liquid to solid, reduce internal energy  

  Sublimation: solids turns directly to gas 

  Evaporation: liquid turns to gas  
• Changes in state, mass are always conserved. They’re physical changes, if you reverse the change, the material recovers its original properties. 
• Heating graph

  • temp of solid rises and this increases energy of particles. The is energy placed into weaking/breaking bonds between particles and this causes the substance (solid) to change state and melt
  • temp of liquid rises- increase of energy in particles. Liquid begins to boild, there's energy breaking/weaking forces of attraction between particles, has become a gas

  (continues to have a temp increase after)
• Latent heat: energy required for a substance to change state

  • during change in state- there's an increase in the internal energy store not a change in temperature
• Specific latent heat of fusion: amount of energy required to change 1kg of a substance from a solid  to liquid with no change in temp
• Specific latent heat of vaporisation:

  amount of energy required to change 1kg of a substance from a liquid  to a vapour with no change in temp

  energy for change of state (J) = mass (kg) x specific latent heat (J/kg)

  
• Particle Motion in Gases

  By colliding with the walls of the container, gas particles are exerting a pressure

  • To increase the pressure, you have to increase the number of collisions/energy of each collision (increase temp) 
  • The temperature gas is relative to the average kinetic energy of the particles 
• Low Pressure

  Low temperature- particles have low kinetic energy. There are fewer collison per second and low energy collisions

  High Pressure

  High temperature- particles have high kinetic energy. There are more collison per second and higher energy collisions