P3: Particle Model Of Matter

• Density

  The mass (kg) per unit volume (m³) of an object
• Particle Model

  • Can explain density and the three states of matter
• The density of a material depends on the kind of particles and how they are arranged
• Warming a material

  Particles move closer together, decreasing the volume but not the mass
• States of matter

  • Solid
  • Liquid
  • Gas
• Solids


  • Particles held close together in a fixed arrangement
  • Particles can only vibrate about their positions
  • Highest density
• Liquids

  • Particles have weaker forces of attraction
  • Particles move in random directions at low speeds
  • Generally less dense than solids
• Gases

  • Almost no forces of attraction between particles
  • Particles have high energy 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

  3. Calculate density using formula
• To find the density of a liquid

  1. Measure mass of known volume

  2. Repeat for different volumes

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

  The energy stored by the particles that make up a system
• Heating a system transfers energy to its particles, increasing their kinetic energy and temperature
• A change in state occurs if the substance is heated enough for the particles to break the bonds holding them together
• Changes of state are physical changes, not chemical changes
• Mass is conserved during changes of state
• Specific latent heat


  The energy needed to change the state of 1 kg of a substance without changing its temperature
• The specific latent heat of vaporisation for water is 2,260,000 J/kg
• The average energy in the kinetic stores of gas particles is related to the temperature
• Colliding gas particles

  • Create pressure on the container walls
• Increasing temperature of a gas

  Increases the speed and frequency of particle collisions, increasing pressure
• Increasing volume of a gas at constant temperature

  Decreases the pressure
• The relationship between pressure and volume of a gas at constant temperature is PV = constant
• Decreasing external pressure on a container can cause it to expand
• Doing work on a gas can increase its temperature by increasing the kinetic energy of the particles