Magnesium metal burns in air producing intense light Magnesium Burning

Demonstration  The reaction was initiated in a flame  The reaction produced intense light  The magnesium reacted with the oxygen and nitrogen in the atmosphere to form solid products

Purpose  To observe a metal while it burns

Concepts 1.Combustion Reactions 2.Combination Reactions 3.Energy

1.Combustion Reactions  “Burning” reactions  Usually organic substances  wood  paper  By definition a combustion reaction is the exothermic reaction of a substance, usually with oxygen (but not always)  Light typically is also a product of the reaction  Metals also burn!

2.Combination Reactions  General form  A + B C  In this demonstration  2 Mg+ O 2 MgO  3 Mg + N 2 Mg 3 N 2  The oxygen and nitrogen occur naturally in the atmosphere  O 2 is 21% of air  N 2 is 78% of air

3.Energy  Two types of energy are produced in this demonstration  heat energy  H f MgO = kJ/mole (kiloJoules per mole)  this is said to be the ‘heat of formation’ for MgO  the negative sign indicates the formation is exothermic  light energy  approximately 10% of the energy of combustion occurs as light in this demonstration  more light than any other known reaction

Conclusions  When the energy of activation was applied magnesium burst into flame  Magnesium burned with the intense production of light and heat  The reaction was a combination reaction which used gaseous components from the atmosphere

Comments  This is a redox reaction in addition to a combination and combustion reaction  Mg begins as oxidation number 0  In both magnesium oxide and magnesium nitride the oxidation number of magnesium is 2+  magnesium has lost electrons therefore has been oxidized  Flashbulbs contain magnesium filaments