P3: Particle Model e of Matter

• Particle model of matter


  Everything is made up of lots of tiny particles
• Particle model


  • Can explain density and the three states of matter
• Density


  A measure of the 'compactness' of a substance, relating the mass of a substance to how much space it takes up
• The symbol for density is a Greek letter
• Density can also be given in g/cm³ or 1000 kg/m³
• Density of an object

  • Depends on what it's made of and how its particles are arranged
  • A dense material has its particles packed tightly together, a less dense material has its particles more spread out
• The three states of matter

  • Solid
  • Liquid
  • Gas
• Solids


  • Strong forces of attraction hold the particles close together in a fixed, regular arrangement
  • Particles don't have much energy so they can only vibrate about their fixed positions
  • Density is generally highest in this state
• Liquids


  • Weaker forces of attraction between the particles
  • Particles are close together but can move past each other and form irregular arrangements
  • Particles have more energy than in solids and move in random directions at low speeds
  • Generally less dense than solids
• Gases


  • Almost no forces of attraction between the particles
  • Particles have more energy than in liquids and solids, are free to move and travel in random directions at high speeds
  • Generally less dense than liquids
• To find the density of a solid object

  1. Measure mass

  2. Measure volume (regular solid or irregular solid using Eureka can)

  3. Plug mass and volume into density formula
• To find the density of a liquid

  1. Place measuring cylinder on balance and zero

  2. Pour 10 ml of liquid into cylinder and record mass

  3. Repeat for full cylinder, recording total volume and mass

  4. Calculate density for each measurement and take average
• The volume of a cube is equal to length x width x height
• Internal energy


  The total energy that the particles (atoms and molecules) in a system have in their kinetic and potential energy stores
• Heating a system


  Transfers energy to its particles, increasing their kinetic energy and internal energy
• Changes in temperature depend on mass, specific heat capacity, and energy input
• Change of state


  Occurs when particles have enough energy in their kinetic energy stores to break the bonds holding them together
• Changes of state


  • Solid to gas (sublimating)
  • Liquid to gas (boiling or evaporating)
  • Solid to liquid (melting)
  • Gas to liquid (condensing)
  • Liquid to solid (freezing)
• Changes of state are physical changes, not chemical changes
• Mass is conserved during changes of state
• Latent heat


  The energy needed to change the state of a substance
• Specific latent heat


  The amount of energy needed to change 1 kg of a substance from one state to another without changing its temperature
• Specific latent heat of fusion


  The specific latent heat for changing between a solid and a liquid
• Specific latent heat of vaporisation


  The specific latent heat for changing between a liquid and a gas
• The specific latent heat of vaporisation for water is 2,260,000 J/kg
• Temperature


  Related to the average energy in the kinetic energy stores of the particles in a gas
• Increasing temperature


  Increases the average energy in the kinetic energy stores of gas particles
• Colliding gas particles


  • Create pressure by exerting a force on the container walls
• Increasing temperature or decreasing volume

  Increases gas pressure
• Increasing volume or decreasing pressure

  Decreases gas pressure
• Changing pressure on a container

  • Can cause the container to compress or expand
• Doing work on a gas

  Increases its internal energy and temperature