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How does sublimation change dry ice into carbon dioxide gas?

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Diagram showing four physical states of matter: solid with tightly packed molecules, liquid with loosely packed molecules, gas with widely spaced molecules, and plasma with free electrons and nuclei, each labeled with descriptions and an arrow indicating increasing energy. — phase States of matter.

Sublimation is the process by which a substance transitions directly from a solid to a gas without passing through a liquid phase.12

In the case of dry ice, which is solid carbon dioxide, this occurs because its triple-point pressure is higher than normal atmospheric pressure. At standard atmospheric pressure, the sublimation curve—which represents the equilibrium between the solid and gaseous states—is crossed when the temperature reaches −78.5 °C (−109.3 °F).314

Because the environmental pressure is below the triple point, the solid carbon dioxide cannot exist as a liquid and instead converts directly into vapor. This phase change is highly efficient, with dry ice expanding into carbon dioxide gas at a ratio of approximately 1:850.34