| Term: | Ice |
| Definition: |
The solid form of water. It can be found in the atmosphere in the form of ice crystals, snow, ice pellets, and hail for example. CanadaNCA
(1) Ice is the solid form of water. It is a transparent crystalline material having adensity of 917 kg m-3 for pure, bubble-free ice at 0 IACSSnow Water substance in the solid phase. Ice can occur in many forms. At and near the Earth's surface, ice always crystallizes in the hexagonal system. This phase is designated ice Ih, the Roman numeral I distinguishing it from more than a dozen other phases and the letter h distinguishing it from the metastable cubic phase ice Ic. See, among other articles, glacier ice and diamond dust. IHPGlacierMassBalance The solid crystalline form of water. NSIDCCryosphere Solid form of water. WMOHydrology Water in the solid state IPAPermafrost Water in solid state. Ice commonly occurs as hexagonal crystals. In Permafrost regions, Ice may occupy voids in soils and rocks and may develop in a variety of forms. Ice may be colourless to pale blue or greenish-blue. It may appear white due to included gas bubbles; in exposures, Ground Ice may also appear black. TrombottoGeocryology The solid, crystalline form of water substance; it is found in the atmosphere as snow crystals, hail, ice pellets, etc., and on the earth's surface in forms such as hoarfrost, rime, glaze, sea ice, glacier ice, ground ice, frazil, anchor ice, etc. This form of water is, strictly speaking, called ice I, the only one of the several known modifications of solid water substance that is stable at commonly occurring temperatures and pressures. (Some of the other forms have very unusual properties, ice VII, for example, being stable only at pressures above 22 400 kg/cm^2, but then existing at temperatures up to about 100C.) Ice has an open structure because the water molecules bond to their neighbors covalently only in four directions; it therefore floats on higher density water, where broken molecular bonds permit closer packing. All commonly occurring forms of ice are crystalline, although large single crystals are relatively rare except in glaciers. The ice crystal lattice possesses hexagonal symmetry that manifests itself in the gross forms of such single crystals as are sometimes found in snow. At an air pressure of one atmosphere, ice melts at 0C by definition of the Celsius temperature scale. (Strictly at equilibrium among water, ice, and vapor occurs at +0.01C, the triple point.) On the other hand, ice does not invariably form in liquid water cooled below this temperature; it has a tendency to supercool, more so in the absence of ice nuclei. AMSglossary Frozen form of the water molecule. Ice has a specific gravity (0.9166) which is slightly less than water. This difference in specific gravity causes ice to float on water. PhysicalGeography The solid form of water in nature formed either by: (a) the freezing of water, (b) the condensation of atmospheric water vapour direct into ice crystals, (c) the compaction of snow with or without the motion of a glacier, or (d) the impregnation of porous snow masses with water which subsequently freezes. SPRI GCW |