Dry ice is the solid form of what substance?

The story behind the answer

Dry ice is the solid form of carbon dioxide (CO2). At normal atmospheric pressure, CO2 doesn’t melt; it sublimates—changing directly from solid to gas at about −78.5°C (−109.3°F). That’s why it’s called “dry”: it cools things without leaving a liquid puddle like water ice.

The dense, cold CO2 gas from dry ice is useful for refrigeration, shipping perishables, and creating theatrical fog. Unlike nitrogen (liquid at much colder −196°C), ammonia, or oxygen, CO2’s phase behavior at everyday pressures makes it practical to handle as a solid. Memory tip: