The graph shows phases and phase changes...

• Phases are shown when the graph is growing 
  • The lowest (to the bottom) of the graph is always where there is a solid
  • The middle is always where there is a liquid
  • The top is always where there is a gas 
• Phase Changes are shown when the graph levels off or stays the same
  • The one lowest (between solid and liquid) is melting point
  • The one highest (between liquid and gas) is boiling point
• With each phase change more energy is added