Changes of state

• What happens during melting and boiling:

  • Substance heats up
  • Particles gain energy
  • Forces between particles weaken
  • Particles break free from position
• What happens during condensing and freezing:

  • Substance cools down
  • Particles lose energy
  • Forces between particles form
  • Particles are held in position
• A pure substance will boil and melt at a fixed temperature. While, impure substance / mixture will melt over a range of temperatures.
• Combustion - a chemical reaction where a substance reacts rapidly with oxygen and gives off heat