Key concepts:

• The rapidly moving oxygen molecules constantly crash into the hydrocarbon wax molecules in the candle, but nothing happens.
• Nothing happens because the molecular collisions do not have enough force to break apart the reacting molecules.
• When a lighted match is placed next to the wick of the candle, the heat from the burning match is transferred to the moving oxygen molecules.
  The extra energy makes the oxygen molecules move faster and faster.
• When the fast oxygen molecules crash into the hydrocarbon molecules, they cause a chemical reaction to take place.
• The flame of the candle is the spontaneous chemical reaction that is giving off energy (the light and heat).
• The burning match supplied just enough energy to get the reaction started.
• The extra heat energy pushes the reaction over the activation energy barrier.