Internal Energy and Changes of State

• Internal Energy


  • Stored by the particles that make up a system
  • Particles have energy in their kinetic energy stores
  • Particles have energy in their potential energy stores due to their positions
• Internal energy of a system

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


  1. Transfers energy to its particles

  2. Particles gain energy in their kinetic stores and move faster

  3. Increases the internal energy
• Increase in internal energy

  Leads to a change in temperature or a change in state
• Specific heat capacity


  Determines the size of the temperature change for a given energy input
• Change in state


  Particles have enough energy in their kinetic energy stores to break the bonds holding them together
• A change of state is a physical change, not a chemical change
• Mass is conserved during a change of state, as the number of particles doesn't change, they're just arranged differently
• Changes of state


  • Sublimating
  • Melting
  • Freezing
  • Boiling or evaporating
  • Condensing