Ice

Ice is the name given to any one of the 14 known solid phases of water. Though in non-scientific contexts, it usually describes ice Ih, which is the most abundant of these phases. It is a crystalline solid, which can appear transparent or an opaque bluish-white color depending on the presence of impurities such as air. The addition of other materials such as soil may further alter appearance. The most common phase transition to ice Ih occurs when liquid water is cooled below 0 °C (273.15 K, 32 °F) at standard atmospheric pressure. However, it can also deposit from a vapor with no intervening liquid phase such as in the formation of frost. Ice appears in varied forms such as hail, ice cubes, and glaciers. It plays an important role with many meteorological phenomena. The ice caps of the polar regions are of significance for the global climate and particularly the water cycle.