Note:  Contact The Fire Systems Group at Michael.Mari@colorado.edu ANDJohn.Humphrey@colorado.edu (email BOTH) ahead of time to have the smoke alarms disabled during the class period when thermite will be performed.

Introduction

Magnesium ribbon is burned in the presence of oxygen and in a CO2 atmosphere.

2Mg(s) + O2(g)  → 2MgO(s)

2Mg(s) + CO2(g)  →  2MgO(s) + C(s) 

Magnesium in dry ice

To Conduct Demonstration 

Caution: Do not look directly at the burning magnesium!

  1. Prop open exit door in Chem 140.
  2. On a wire cart, invert a large square plastic container and place the heat resistant mat on top.  Place the hollowed out piece of dry ice on top of the heat resistant mat. Place magnesiumturnings into the hollow of the bottom slab of dry ice immediately before lighting.  Ignite with the propane torch.  Keep the flame in contact with the magnesium until the metal is white hot.
  3. Place the second block of dry ice on top of the burning magnesium.
  4. Turn off the lights.  The dry ice blocks will begin to glow and spark.
  5. After magnesium is completely consumed, show black specks (carbon) and white powder (MgO) produced.

 Demo Time: ~5 - 10 minutes

Safety 

Light given off by burning magnesium is very bright and should not be viewed directly.  The magnesium in dry ice can spew burning magnesium in any direction and should not be performed in a carpeted room.  A safety shield should be placed between the dry ice and the audience or position the cart well back from the front row.

Acknowledgment:

Henry Bent, Fall 1988; Steven Zumdahl, Fall 1990.
Revised 2/2012