Discussion

This is a very striking demonstration of the considerable reducing strength of magnesium and the very great stability of magnesium oxide. One might expect that the low temperature of the dry ice would prevent reaction by slowing it down. The relative stability of carbon dioxide also would argue against reaction. But the reaction is exothermic and the temperature rapidly increases to the point where reaction occurs.

Narration

Magnesium is placed in a cavity in a block of dry ice. The magnesium is ignited and covered by another block of dry ice. Despite the absence of air, the magnesium continues to glow, due to its reaction with carbon dioxide. Because of this reaction, carbon dioxide cannot be used to extinguish magnesium fires. The reaction products are white magnesium oxide and black carbon.