We did this in HS chem class, with a block of dry ice that we cut in half and hollowed out. Then we coiled up some magnesium ribbon so it would perch in the hol

We did this in HS chem class, with a block of dry ice that we cut in half and hollowed out. Then we coiled up some magnesium ribbon so it would perch in the hole, lit it with a MAPP gas torch, and closed the block. The magnesium continued to burn long after any lingering air in the hollow could've been consumed. After a few minutes the magnesium was gone and we opened the block, and there was black carbon dust in the bottom of the hollow. And that introduced the conversation about using the right extinguisher for the job!