Internal energy

• Internal energy


  The energy stored in a system by the particles, which is the total kinetic energy and potential energy of all the atoms and molecules that make up the system
• Heating a solid


  1. Increases the internal energy

  2. Solid turns into a liquid (melting)
• Heating a liquid


  1. Increases the internal energy

  2. Liquid turns into a gas (boiling)
• Cooling a gas


  1. Reduces the internal energy

  2. Gas turns into a liquid (condensation)
• Cooling a liquid


  1. Reduces the internal energy

  2. Liquid turns into a solid (freezing)
• Sublimation


  A solid turning directly into a gas
• Mass is always conserved during changes of state
• Changes of state are physical changes, not chemical changes
• Evaporation


  A liquid turning into a gas, but only on the surface of the liquid
• Particles on the surface of a liquid have enough energy to turn into a gas during evaporation