Particle model 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 its mass to the space it takes up
• 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
• Three states of matter

  • Solid
  • Liquid
  • Gas
• Solid


  • 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
• Liquid


  • 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
• Gas


  • 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
• Individual gas particles move at quite a range of different speeds
• Internal energy


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


  1. Transfers energy to the particles, increasing their kinetic energy and internal energy

  2. Can lead to a change in temperature or a change in state
• A change of state conserves mass - the number of particles doesn't change, they're just arranged differently
• 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
• The specific latent heat of vaporisation for water (boiling) is 2,260,000 J/kg
• The average energy in the kinetic energy stores of gas particles is related to the temperature of the gas
• Colliding gas particles


  • Create pressure as they bang into each other and the container walls
• Increasing temperature


  Increases the speed of gas particles, leading to an increase in pressure (if volume is constant)
• Increasing volume


  Decreases the pressure of a gas (if temperature is constant)
• Change in pressure


  • Can cause a change in volume if the container can easily change size
• Doing work on a gas

  Increases its internal energy and can increase its temperature