Deposition (phase transition)

Deposition is the phase transition in which a gas turns directly into a solid without passing through a liquid stage; the reverse process is called sublimation. The change is exothermic, releasing thermal energy as the gas solidifies. It occurs naturally when water vapor in sub-freezing air loses enough thermal energy, once the air temperature falls below the dew point, to form ice crystals directly, skipping the liquid phase entirely. This is how frost and hoar frost form on leaves, grass, and windows in cold weather, producing the branching crystalline patterns often seen on winter glass as humid air deposits its water vapor straight into solid ice. This description is adapted from Wikipedia contributors under CC BY-SA 4.0; changes were made. https://creativecommons.org/licenses/by-sa/4.0/