A glacier is made from ice, itselfresulting from snow accumulation.

Frozen water in the form of anordinary (household) ice cube. Thewhite zone in the center is due to tinyair bubbles.

Snowflakes by Wilson Bentley, 1902.Snow is ice that grows from watervapor in Earth's atmosphere, which iswhy it usually displays crystal shapes.

IceFrom Wikipedia, the free encyclopedia

Ice is water frozen into a solid state. It can appear transparent or opaquebluish-white color, depending on the presence of impurities such as soilparticles or air inclusions.

It occurs naturally throughout the Solar System from as close to the Sun asMercury to the Oort Cloud and beyond as interstellar ice. Ice is abundant onEarth's surface, particularly in the polar regions as polar ice caps and abovethe snow line.[1]

On Earth, ice is an important component of the global climate and plays animportant role in the water cycle. Geologically, ice formations includeglaciers, ice sheets, sea ice and icebergs. It is a common form ofprecipitation and deposition on Earth, falling as snowflakes and hail oroccurring as frost, icicles or ice spikes.

Ice is used for a wide range of applications including cooling, winter sportsand the art of ice sculpting.

The molecules in ice may have different geometries, or phases, dependingon temperature and pressure. The hexagonal crystal form of ordinary ice isthe most abundant on the Earth's surface and is denoted as ice Ih, (ice oneh). The most common phase transition to ice Ih occurs when liquid water iscooled below 0 C (273.15 K, 32 F) at standard atmospheric pressure. Itcan also deposit from vapour with no intervening liquid phase, such as in theformation of frost.

The word is derived from Old English s, which in turn stems from Proto-Germanic isaz.

Contents

1 Characteristics1.1 Slipperiness

2 Natural formation2.1 Ice on the oceans2.2 Ice on land and structures2.3 Ice on rivers and streams2.4 Ice on lakes2.5 Ice in the air

2.5.1 Rime ice2.5.2 Ice pellets2.5.3 Hail2.5.4 Snowflakes2.5.5 Diamond dust

3 Production3.1 Ice harvesting3.2 Commercial production

4 Uses4.1 Sports4.2 Other uses

5 Ice and transportation

Crystal structure of hexagonal ice.Grey dashed lines indicate hydrogenbonds.

6 Phases7 Other ices8 See also9 References10 External links

Characteristics

As a naturally-occurring crystalline inorganic solid with an orderedstructure, ice is considered a mineral.[2] It possesses a regular crystallinestructure based on the molecule of water, which consists of a single oxygenatom covalently bonded to two hydrogen atoms, or H-O-H. However, manyof the physical properties of water and ice are controlled by the formation ofhydrogen bonds between adjacent oxygen and hydrogen atoms; while it is aweak bond, it is nonetheless critical in controlling the structure of both waterand ice.

An unusual property of ice frozen at atmospheric pressure is that the solid isapproximately 8.3% less dense than liquid water. The density of ice is0.9167 g/cm3 at 0 C,[3] whereas water has a density of 0.9998 g/cm at thesame temperature. Liquid water is densest, essentially 1.00 g/cm, at 4 Cand becomes less dense as the water molecules begin to form the hexagonalcrystals[4] of ice as the freezing point is reached. This is due to hydrogen

bonding dominating the intermolecular forces, which results in a packing of molecules less compact in the solid.Density of ice increases slightly with decreasing temperature and has a value of 0.9340 g/cm at 180 C (93 K).[5]

The effect of expansion during freezing can be dramatic, and ice expansion is a basic cause of freeze-thawweathering of rock in nature and damage to building foundations and roadways from frost heaving. It is also acommon cause of the flooding of houses when water pipes burst due to the pressure of expanding water when itfreezes.

The result of this process is that ice (in its most common form) floats on liquid water, which is an important feature inEarth's biosphere. It has been argued that without this property natural bodies of water would freeze, in some casespermanently, from the bottom up,[6] resulting in a loss of bottom-dependent animal and plant life in fresh and seawater. Sufficiently thin ice sheets allow light to pass through while protecting the underside from short-term weatherextremes such as wind chill. This creates a sheltered environment for bacterial and algal colonies. When sea waterfreezes, the ice is riddled with brine-filled channels which sustain sympagic organisms such as bacteria, algae,copepods and annelids, which in turn provide food for animals such as krill and specialised fish like the Baldnotothen, fed upon in turn by larger animals such as Emperor penguins and Minke whales.[7]

When ice melts, it absorbs as much energy as it would take to heat an equivalent mass of water by 80 C. During themelting process, the temperature remains constant at 0 C. While melting, any energy added breaks the hydrogenbonds between ice (water) molecules. Energy becomes available to increase the thermal energy (temperature) onlyafter enough hydrogen bonds are broken that the ice can be considered liquid water. The amount of energyconsumed in breaking hydrogen bonds in the transition from ice to water is known as the heat of fusion.

As with water, ice absorbs light at the red end of the spectrum preferentially as the result of an overtone of anoxygen-hydrogen (O-H) bond stretch. Compared with water, this absorption is shifted toward slightly lowerenergies. Thus, ice appears blue, with a slightly greener tint than for liquid water. Since absorption is cumulative, thecolor effect intensifies with increasing thickness or if internal reflections cause the light to take a longer path throughthe ice.[8]

Frozen waterfall in southeast NewYork

Feather ice on the plateau near Alta,Norway. The crystals form attemperatures below 30 C (i.e.22 F).

Other colors can appear in the presence of light absorbing impurities, where the impurity is dictating the color ratherthan the ice itself. For instance, icebergs containing impurities (e.g., sediments, algae, air bubbles) can appear brown,grey or green.[8]

Slipperiness

Ice was originally thought to be slippery due to the pressure of an objectcoming into contact with the ice, creating heat, melting a thin layer of the iceand allowing the object to glide across the surface.[citation needed] Forexample, the blade of an ice skate, upon exerting pressure on the ice, wouldmelt a thin layer, providing lubrication between the ice and the blade. Thisexplanation, called "pressure melting", originated in 19th century. Ithowever did not account for skating on ice temperatures lower than 3.5 C,which skaters often skate upon.

In the 20th century an alternative explanation, called "friction heating," wasproposed, whereby friction of the material was the cause of the ice layermelting. However, this theory also failed to explain skating at lowtemperature. Neither sufficiently explained why ice is slippery when standing still even at below-zerotemperatures.[9]

It is now believed that ice is slippery because ice molecules in contact with air cannot properly bond with themolecules of the mass of ice beneath (and thus are free to move like molecules of liquid water). These moleculesremain in a semi-liquid state, providing lubrication regardless of pressure against the ice exerted by any object.However, the significance of this hypothesis is disputed by experiments showing a high coefficient of friction for iceusing atomic force microscopy. [10]

Natural formation

The term that collectively describes all of the parts of the Earth's surfacewhere water is in frozen form is the cryosphere. Ice is an importantcomponent of the global climate, particularly in regard to the water cycle.Glaciers and snowpacks are an important storage mechanism for freshwater; over time, they may sublimate or melt. Snowmelt is often animportant source of seasonal fresh water. The World MeteorologicalOrganization defines several kinds of ice depending on origin, size, shape,influence and so on.[11] Clathrate hydrates are forms of ice that containgas molecules trapped within its crystal lattice.

Ice on the oceans

Main article: Sea ice

Ice that is found at sea may be in the form of drift ice floating in the water, fast ice fixed to a shoreline or anchor iceif attached to the sea bottom. Ice which calves (breaks off) from a ice shelf or glacier may become an ice berg. Seaice can be forced together by currents and winds to form pressure ridges up to 12 metres (39 ft) tall. Navigationthrough areas of sea ice occurs in openings called polynyas or leads or requires the use of a special ship called anicebreaker.

Ice on land and structures

Ice on land range from the largest type called an ice sheet to smaller ice caps and ice fields to glaciers and ice streamsto the snow line and snow fields.

Ice on conifer after freezing rain

A small frozen rivulet

Aufeis is layered ice that forms in Arctic and subarctic stream valleys. Ice, frozen in the stream bed, blocks normal

groundwater discharge, and causes the local water table to rise, resulting in water discharge on top of the frozen

layer. This water then freezes, causing the water table to rise further and

repeat the cycle. The result is a stratified ice deposit, often several meters

thick.

Freezing rain is a type of winter storm called an ice storm where rain falls

and then freezes producing a glaze of ice. Ice can also form icicles, similar to

stalactites in appearance, or stalagmite-like forms as water drips and re-

freezes.

The term ice dam has three meanings (others discussed below). On

structures an ice dam is the buildup of ice on a sloped roof which stops melt

water from draining properly and can cause damage from water leaks in

buildings.

Ice on rivers and streams

Ice which forms on moving water tends to be less uniform and stable than ice

which forms on calm water. Ice jams (sometimes called an ice dam), when

broken chunks of ice pile up, are the greatest ice hazard on rivers. Ice jams can

cause flooding, damage structures in or near the river, and damage vessels in

the river. Ice jams can cause some hydropower industrial facilities to completely

shut down. An ice dam is a dam (blockage) from the movement of a glacier

which may produce a proglacial lake. Heavy ice flows in rivers can also

damage vessels and require the use of an icebreaker to keep navigation

possible.

Ice discs are circular formations of ice surrounded by water in a river.

Pancake ice is a formation of ice generally created in areas with less calm conditions.

Ice on lakes

Ice forms on calm water from the shores, a thin layer spreading across the surface, and then downward. Ice on lakes

is generally four types: Primary, secondary, superimposed and agglomerate.[12][13] Primary ice forms first.

Secondary ice forms below the primary ice in a direction parallel to the direction of the heat flow. Superimposed ice

forms on top of the ice surface from rain or water which seeps up through cracks in the ice which often settles when

loaded with snow.

Shelf ice is when floating pieces of ice are driven by the wind piling up on the windward shore.

Candle ice is a form of rotten ice that develops in columns perpendicular to the surface of a lake.

Ice in the air

Rime ice

Rime is a type of ice formed on cold objects when drops of water crystallize on them. This can be observed in foggy

weather, when the temperature drops during the night. Soft rime contains a high proportion of trapped air, making it

appear white rather than transparent, and giving it a density about one quarter of that of pure ice. Hard rime is

comparatively denser.

Ice pellets

An accumulation of ice pellets

A large hailstone, about 6 cm (2.36in) in diameter

See also: Ice pellets

Ice pellets are a form of precipitation consisting of small, translucent balls ofice. This form of precipitation is also referred to as sleet by the United StatesNational Weather Service.[14] (In Commonwealth English "sleet" refers to amixture of rain and snow). Ice pellets are usually (but not always) smallerthan hailstones.[15] They often bounce when they hit the ground, andgenerally do not freeze into a solid mass unless mixed with freezing rain.The METAR code for ice pellets is PL.[16]

Ice pellets form when a layer of above-freezing air is located between 1,500metres (4,900 ft) and 3,000 metres (9,800 ft) above the ground, with sub-freezing air both above and below it. This causes the partial or completemelting of any snowflakes falling through the warm layer. As they fall back into the sub-freezing layer closer to thesurface, they re-freeze into ice pellets. However, if the sub-freezing layer beneath the warm layer is too small, theprecipitation will not have time to re-freeze, and freezing rain will be the result at the surface. A temperature profileshowing a warm layer above the ground is most likely to be found in advance of a warm front during the coldseason,[17] but can occasionally be found behind a passing cold front.

Hail

See also: Hail

Like other precipitation, hail forms in storm clouds when supercooled waterdroplets freeze on contact with condensation nuclei, such as dust or dirt. Thestorm's updraft blows the hailstones to the upper part of the cloud. Theupdraft dissipates and the hailstones fall down, back into the updraft, and arelifted up again. Hail has a diameter of 5 millimetres (0.20 in) or more.[18]

Within METAR code, GR is used to indicate larger hail, of a diameter of atleast 6.4 millimetres (0.25 in) and GS for smaller.[16] Stones just larger thangolf ball-sized are one of the most frequently reported hail sizes.[19]

Hailstones can grow to 15 centimetres (6 in) and weigh more than .5kilograms (1.1 lb).[20] In large hailstones, latent heat released by furtherfreezing may melt the outer shell of the hailstone. The hailstone then mayundergo 'wet growth', where the liquid outer shell collects other smaller hailstones.[21] The hailstone gains an icelayer and grows increasingly larger with each ascent. Once a hailstone becomes too heavy to be supported by thestorm's updraft, it falls from the cloud.[22]

Hail forms in strong thunderstorm clouds, particularly those with intense updrafts, high liquid water content, greatvertical extent, large water droplets, and where a good portion of the cloud layer is below freezing 0 C (32 F).[18]

Hail-producing clouds are often identifiable by their green coloration.[23][24] The growth rate is maximized at about13 C (9 F), and becomes vanishingly small much below 30 C (22 F) as supercooled water droplets becomerare. For this reason, hail is most common within continental interiors of the mid-latitudes, as hail formation isconsiderably more likely when the freezing level is below the altitude of 11,000 feet (3,400 m).[25] Entrainment ofdry air into strong thunderstorms over continents can increase the frequency of hail by promoting evaporationalcooling which lowers the freezing level of thunderstorm clouds giving hail a larger volume to grow in. Accordingly,hail is actually less common in the tropics despite a much higher frequency of thunderstorms than in the mid-latitudesbecause the atmosphere over the tropics tends to be warmer over a much greater depth. Hail in the tropics occursmainly at higher elevations.[26]

Snowflakes

Main article: Snowflake

Snowflake viewed in an opticalmicroscope

Harvesting ice on Lake St. Clair inMichigan, c. 1905

B&W film of 1919 ice harvest atPocono Manor in the Poconos

Snow crystals form when tiny supercooled cloud droplets (about 10 m indiameter) freeze. These droplets are able to remain liquid at temperatureslower than 18 C (255 K; 0 F), because to freeze, a few molecules in thedroplet need to get together by chance to form an arrangement similar to thatin an ice lattice; then the droplet freezes around this "nucleus." Experimentsshow that this "homogeneous" nucleation of cloud droplets only occurs attemperatures lower than 35 C (238 K; 31 F).[27] In warmer clouds anaerosol particle or "ice nucleus" must be present in (or in contact with) thedroplet to act as a nucleus. Our understanding of what particles makeefficient ice nuclei is poor what we do know is they are very rarecompared to that cloud condensation nuclei on which liquid droplets form.Clays, desert dust and biological particles may be effective,[28] although towhat extent is unclear. Artificial nuclei are used in cloud seeding.[29] Thedroplet then grows by condensation of water vapor onto the ice surfaces.

Diamond dust

See also: Diamond dust

So-called "Diamond dust," also known as ice needles or ice crystals, forms at temperatures approaching 40 C(40 F) due to air with slightly higher moisture from aloft mixing with colder, surface based air.[30] The METARidentifier for diamond dust within international hourly weather reports is IC.[16]

Production

Ice is now mechanically produced on a large scale, but before refrigerationwas developed ice was harvested from natural sources for human use.

Ice harvesting

Main article: Ice cutting

Ice has long been valued as a means of cooling. In 400 BC Iran, Persianengineers had already mastered the technique of storing ice in the middle ofsummer in the desert. The ice was brought in during the winters from nearbymountains in bulk amounts, and stored in specially designed, naturallycooled refrigerators, called yakhchal (meaning ice storage). This was alarge underground space (up to 5000 m) that had thick walls (at least twometers at the base) made of a special mortar called srooj, composed ofsand, clay, egg whites, lime, goat hair, and ash in specific proportions, andwhich was known to be resistant to heat transfer. This mixture was thoughtto be completely water impenetrable. The space often had access to a qanat,and often contained a system of windcatchers which could easily bringtemperatures inside the space down to frigid levels on summer days. The icewas used to chill treats for royalty.

There were thriving industries in 16th/17th century England whereby lowlying areas along the Thames Estuary were flooded during the winter, andice harvested in carts and stored inter-seasonally in insulated wooden housesas a provision to an icehouse often located in large country houses, andwidely used to keep fish fresh when caught in distant waters. This wasallegedly copied by an Englishman who had seen the same activity in China. Ice was imported into England fromNorway on a considerable scale as early as 1823.[31]

An ice manufacturing plant in EastMidnapore, India

Ice sailing on the nin Small Lake

In the United States, the first cargo of ice was sent from New York City to Charleston, South Carolina in 1799,[31]

and by the first half of the 19th century, ice harvesting had become big business. Frederic Tudor, who becameknown as the Ice King, worked on developing better insulation products for the long distance shipment of ice,especially to the tropics; this became known as the ice trade.

Trieste sent ice to Egypt, Corfu, and Zante; Switzerland sent it to France;and Germany sometimes was supplied from Bavarian lakes.[31] Untilrecently, the Hungarian Parliament building used ice harvested in the winterfrom Lake Balaton for air conditioning.

Ice houses were used to store ice formed in the winter, to make ice availableall year long, and early refrigerators were known as iceboxes, because theyhad a block of ice in them. In many cities, it was not unusual to have aregular ice delivery service during the summer. The advent of artificialrefrigeration technology has since made delivery of ice obsolete.

Ice is still harvested for ice and snow sculpture events. For example, a swingsaw is used to get ice for the Harbin International Ice and Snow Sculpture Festival each year from the frozen surfaceof the Songhua River.[32]

Commercial production

Ice is now produced on an industrial scale, for uses including food storage and processing, chemical manufacturing,concrete mixing and curing, and consumer or packaged ice.[33] Most commercial icemakers produce three basictypes of fragmentary ice: flake, tubular and plate, using a variety of techniques.[33] Large batch ice makers canproduce up to 75 tons of ice per day.[34]

Ice production is a large business; in 2002, there were 426 commercial ice-making companies in the United States,with a combined value of shipments of $595,487,000.[35]

For small-scale ice production, many modern home refrigerators can also make ice with a built in icemaker, whichwill typically make ice cubes or crushed ice. Stand-alone icemaker units that make ice cubes are often called icemachines.

Uses

Sports

Ice also plays a central role in winter recreation and in many sports such asice skating, tour skating, ice hockey, bandy, ice fishing, ice climbing,curling, broomball and sled racing on bobsled, luge and skeleton. Many ofthe different sports played on ice get international attention every four yearsduring the Winter Olympic Games.

A sort of sailboat on blades gives rise to ice yachting. The human quest forexcitement has even led to ice racing, where drivers must speed on lake ice,while also controlling the skid of their vehicle (similar in some ways to dirttrack racing). The sport has even been modified for ice rinks.

Other uses

Ice cubes or crushed ice can be used to cool drinks. As the ice melts, it absorbs heat and keeps the drink near0 C (32 F).Ice can be used to reduce swelling (by decreasing blood flow) and pain by pressing it against an area of the

Ice pier during 1983 cargo

operations. McMurdo Station,

Antarctica

U.S. Coast Guard icebreakers near

McMurdo Station, February 2002

body.[36]

Engineers used the formidable strength of pack ice when they

constructed Antarctica's first floating ice pier in 1973.[37] Such ice

piers are used during cargo operations to load and offload ships. Fleet

operations personnel make the floating pier during the winter. They

build upon naturally-occurring frozen seawater in McMurdo Sound

until the dock reaches a depth of about 22 feet (6.7 m). Ice piers have

a lifespan of three to five years.

Structures and ice sculptures are built out of large chunks of ice. The

structures are mostly ornamental (as in the case with ice castles), and

not practical for long-term habitation. Ice hotels exist on a seasonal

basis in a few cold areas. Igloos are another example of a temporary

structure, made primarily from snow.

During World War II, Project Habbakuk was a British programme

which investigated the use of pykrete (wood fibers mixed with ice) as

a possible material for warships, especially aircraft carriers, due to the ease with which a large deck could be

constructed, but the idea was given up when there were not enough funds for construction of a prototype.

Ice can be used to start a fire by carving it into a lens which will focus sunlight onto kindling. A fire will

eventually start.[38]

Ice has even been used as the material for a variety of musical instruments, for example by percussionist Terje

Isungset.[39]

Ice was once used to cool refrigerators in the 19th century, which is reflected in the name "iceboxes."

Ice can be used as part of an air conditioning system.

Ice and transportation

Ice can also be an obstacle; for harbors near the poles, being ice-free is an

important advantage; ideally, all year long. Examples are Murmansk

(Russia), Petsamo (Russia, formerly Finland) and Vard (Norway). Harbors

which are not ice-free are opened up using icebreakers.

Ice forming on roads is a dangerous winter

hazard. Black ice is very difficult to see, because

it lacks the expected frosty surface. Whenever

there is freezing rain or snow which occurs at a

temperature near the melting point, it is common

for ice to build up on the windows of vehicles.

Driving safely requires the removal of the ice

build-up. Ice scrapers are tools designed to break

the ice free and clear the windows, though removing the ice can be a long and laborious

process.

Far enough below the freezing point, a thin layer of ice crystals can form on the inside surface of windows. This

usually happens when a vehicle has been left alone after being driven for a while, but can happen while driving, if

the outside temperature is low enough. Moisture from the driver's breath is the source of water for the crystals. It is

troublesome to remove this form of ice, so people often open their windows slightly when the vehicle is parked in

order to let the moisture dissipate, and it is now common for cars to have rear-window defrosters to solve the

problem. A similar problem can happen in homes, which is one reason why many colder regions require double-

pane windows for insulation.

When the outdoor temperature stays below freezing for extended periods, very thick layers of ice can form on lakes

and other bodies of water, although places with flowing water require much colder temperatures. The ice can

become thick enough to drive onto with automobiles and trucks. Doing this safely requires a thickness of at least

30 cm (one foot).

Ice formation on window glass of

high altitude flying airplane

Pressure dependence of ice melting.

For ships, ice presents two distinct hazards. Spray and freezing rain can produce an ice build-up on the

superstructure of a vessel sufficient to make it unstable, and to require it to be hacked off or melted with steam hoses.

And icebergs large masses of ice floating in water (typically created when glaciers reach the sea) can be

dangerous if struck by a ship when underway. Icebergs have been responsible for the sinking of many ships, the

most famous probably being the Titanic.

For aircraft, ice can cause a number of dangers. As an aircraft climbs, it

passes through air layers of different temperature and humidity, some of

which may be conducive to ice formation. If ice forms on the wings or

control surfaces, this may adversely affect the flying qualities of the aircraft.

During the first non-stop flight across the Atlantic, the British aviators

Captain John Alcock and Lieutenant Arthur Whitten Brown encountered

such icing conditions Brown left the cockpit and climbed onto the wing

several times to remove ice which was covering the engine air intakes of the

Vickers Vimy aircraft they were flying.

A particular icing vulnerability associated with reciprocating internal

combustion engines is the carburetor. As air is sucked through the carburetor

into the engine, the local air pressure is lowered, which causes adiabatic

cooling. So, in humid near-freezing conditions, the carburetor will be colder,

and tend to ice up. This will block the supply of air to the engine, and cause

it to fail. For this reason, aircraft reciprocating engines with carburetors are

provided with carburetor air intake heaters. The increasing use of fuel

injectionwhich does not require carburetorshas made "carb icing" less

of an issue for reciprocating engines.

Jet engines do not experience carb icing, but recent evidence indicates that they can be slowed, stopped, or damaged

by internal icing in certain types of atmospheric conditions much more easily than previously believed. In most

cases, the engines can be quickly restarted and flights are not endangered, but research continues to determine the

exact conditions which produce this type of icing, and find the best methods to prevent, or reverse it, in flight.

Phases

Ice may be any one of the 15 known solid phases of water.

Most liquids under increased pressure freeze at higher

temperatures because the pressure helps to hold the molecules

together. However, the strong hydrogen bonds in water make it

different: For some pressures higher than 1 atm (0.10 MPa),

water freezes at a temperature below 0 C, as shown in the

phase diagram below. The melting of ice under high pressures

is thought to contribute to the movement of glaciers.

Ice, water, and water vapour can coexist at the triple point,

which is exactly 0.01 C (273.16 K) at a pressure of 611.73 Pa

(the Kelvin is in fact defined as 1/273.16 of the difference

between this triple point and absolute zero).[40] Unlike most

other solids, ice is difficult to superheat. In an experiment, ice at

3 C was superheated to about 17 C for about 250

picoseconds.[41]

Subjected to higher pressures and varying temperatures, ice can form in fifteen separate known phases. With care all

these phases except ice X can be recovered at ambient pressure and low temperature. The types are differentiated by

their crystalline structure, ordering and density. There are also two metastable phases of ice under pressure, both

fully hydrogen-disordered; these are IV and XII. Ice XII was discovered in 1996. In 2006, XIII and XIV were

discovered.[42] Ices XI, XIII, and XIV are hydrogen-ordered forms of ices Ih, V, and XII respectively. In 2009, ice

XV was found at extremely high pressures and 143 C.[43] At even higher pressures, ice is predicted to become a

metal; this has been variously estimated to occur at 1.55 TPa[44] or 5.62 TPa.[45]

As well as crystalline forms, solid water can exist in amorphous states as amorphous ice (ASW) of varying densities.

Water in the interstellar medium is dominated by amorphous ice, making it likely the most common form of water in

the universe. Low-density ASW (LDA), also known as hyperquenched glassy water, may be responsible for

noctilucent clouds on earth and is usually formed by deposition of water vapor in cold or vacuum conditions. High

density ASW (HDA) is formed by compression of ordinary ice Ih or LDA at GPa pressures. Very-high density

ASW (VHDA) is HDA slightly warmed to 160K under 12 GPa pressures.

In outer space, hexagonal crystalline ice (the predominant form found on Earth) is extremely rare. Amorphous ice is

more common; however, hexagonal crystalline ice can be formed via volcanic action.[46]

Log-lin pressure-temperature phase diagram of water. The Roman numerals correspond to some ice phases listed below.

Phase Characteristics

Amorphous

ice

Amorphous ice is an ice lacking crystal structure. Amorphous ice exists in three forms: low-density

(LDA) formed at atmospheric pressure, or below, high density (HDA) and very high density

amorphous ice (VHDA), forming at higher pressures. LDA forms by extremely quick cooling of

liquid water ("hyperquenched glassy water", HGW), by depositing water vapour on very cold

substrates ("amorphous solid water", ASW) or by heating high density forms of ice at ambient

pressure ("LDA").

Ice IhNormal hexagonal crystalline ice. Virtually all ice in the biosphere is ice Ih, with the exception only of

a small amount of ice Ic.

Ice Ic

A metastable cubic crystalline variant of ice. The oxygen atoms are arranged in a diamond structure. It

is produced at temperatures between 130 and 220 K, and can exist up to 240 K,[47][48] when it

transforms into ice Ih. It may occasionally be present in the upper atmosphere.[49]

Ice IIA rhombohedral crystalline form with highly ordered structure. Formed from ice Ih by compressing it

at temperature of 190210 K. When heated, it undergoes transformation to ice III.

Ice IIIA tetragonal crystalline ice, formed by cooling water down to 250 K at 300 MPa. Least dense of the

high-pressure phases. Denser than water.

Ice IVA metastable rhombohedral phase. It can be formed by heating high-density amorphous ice slowly at a

pressure of 810 MPa. It doesn't form easily without a nucleating agent.[50]

Ice VA monoclinic crystalline phase. Formed by cooling water to 253 K at 500 MPa. Most complicated

structure of all the phases.[51]

Ice VIA tetragonal crystalline phase. Formed by cooling water to 270 K at 1.1 GPa. Exhibits Debye

relaxation.[52]

Ice VIIA cubic phase. The hydrogen atoms' positions are disordered. Exhibits Debye relaxation. The

hydrogen bonds form two interpenetrating lattices.

Ice VIIIA more ordered version of ice VII, where the hydrogen atoms assume fixed positions. It is formed

from ice VII, by cooling it below 5 C (278 K).

Ice IX

A tetragonal phase. Formed gradually from ice III by cooling it from 208 K to 165 K, stable below

140 K and pressures between 200 MPa and 400 MPa. It has density of 1.16 g/cm3, slightly higher

than ordinary ice.

Ice X Proton-ordered symmetric ice. Forms at about 70 GPa.[53]

Ice XI

An orthorhombic, low-temperature equilibrium form of hexagonal ice. It is ferroelectric. Ice XI is

considered the most stable configuration of ice Ih. The natural transformation process is very slow and

ice XI has been found in Antarctic ice 100 to 10,000 years old. That study indicated that the

temperature below which ice XI forms is 36 C (240 K).[54]

Ice XII

A tetragonal, metastable, dense crystalline phase. It is observed in the phase space of ice V and ice VI.

It can be prepared by heating high-density amorphous ice from 77 K to about 183 K at 810 MPa. It

has a density of 1.3 g cm3 at 127 K (i.e., approximately 1.3 times more dense than water).

Ice XIIIA monoclinic crystalline phase. Formed by cooling water to below 130 K at 500 MPa. The proton-

ordered form of ice V.[55]

Ice XIVAn orthorhombic crystalline phase. Formed below 118 K at 1.2 GPa. The proton-ordered form of ice

XII.[55]

Ice XV The proton-ordered form of ice VI formed by cooling water to around 80108 K at 1.1 GPa.

Other ices

Main article: Volatiles

The solid phases of several other volatile substances are also referred to as ices; generally a volatile is classed as anice if its melting point lies above around 100 K. The best known example is dry ice, the solid form of carbondioxide.

A "magnetic analogue" of ice is also realized in some insulating magnetic materials in which the magnetic momentsmimic the position of protons in water ice and obey energetic constraints similar to the Bernal-Fowler ice rulesarising from the geometrical frustration of the proton configuration in water ice. These materials are called spin ice.

See also

References

Density of ice versus waterIce ageIcebergIce climbingIce famineIce hockeyIce jackingIce roadIce sheetIce skatingJumble icePumpable ice technologySea ice

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8493-0486-5.4. ^ The word crystal derives from Greek word for frost.5. ^ Lide, D. R., ed. (2005). CRC Handbook of Chemistry and Physics (86th ed.). Boca Raton (FL): CRC Press. ISBN 0-

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20. ^ National Severe Storms Laboratory (23 April 2007). "Aggregate hailstone"(http://www.photolib.noaa.gov/htmls/nssl0001.htm). National Oceanic and Atmospheric Administration. Retrieved 15 July2009.

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22. ^ Marshall, Jacque (10 April 2000). "Hail Fact Sheet" (http://www.ucar.edu/communications/factsheets/Hail.html).University Corporation for Atmospheric Research. Retrieved 15 July 2009.

23. ^ Australian Broadcasting Corporation (19 October 2004). "Hail storms rock southern Qld"(http://web.archive.org/web/20100306021712/http://www.abc.net.au/news/australia/qld/toowoomba/200410/s1222665.htm). Archived from the original (http://www.abc.net.au/news/australia/qld/toowoomba/200410/s1222665.htm) on 2010-03-06. Retrieved 15 July 2009.

24. ^ Bath, Michael and Degaura, Jimmy (1997). "Severe Thunderstorm Images of the Month Archives"(http://australiasevereweather.com/storm_news/arc1997.htm). Retrieved 15 July 2009.

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26. ^ Downing, Thomas E.; Olsthoorn, Alexander A. and Tol, Richard S. J. (1999). Climate, change and risk(http://books.google.com/?id=UbtG3vFfNtoC&pg=PA41). Routledge. pp. 4143. ISBN 978-0-415-17031-4.

27. ^ Mason, Basil John (1971). Physics of Clouds. Clarendon Press. ISBN 0-19-851603-7.28. ^ Christner, Brent Q.; Morris, Cindy E.; Foreman, Christine M.; Cai, Rongman and Sands, David C. (2008). "Ubiquity of

Biological Ice Nucleators in Snowfall". Science 319 (5867): 1214. Bibcode:2008Sci...319.1214C(http://adsabs.harvard.edu/abs/2008Sci...319.1214C). doi:10.1126/science.1149757(http://dx.doi.org/10.1126%2Fscience.1149757). PMID 18309078 (//www.ncbi.nlm.nih.gov/pubmed/18309078).

29. ^ Glossary of Meteorology (2009). "Cloud seeding" (http://amsglossary.allenpress.com/glossary/search?p=1&query=cloud+seeding&submit=Search). American Meteorological Society. Retrieved 28 June 2009.

30. ^ Glossary of Meteorology (June 2000). "Diamond Dust" (http://amsglossary.allenpress.com/glossary/search?p=1&query=diamond+dust&submit=Search). American Meteorological Society. Retrieved 21 January 2010.

31. ^ a b c "Ice". Collier's New Encyclopedia. 1921.32. ^ "Ice is money in China's coldest city" (http://www.smh.com.au/travel/ice-is-money-in-chinas-coldest-city-20081113-

62yj.html). AFP via The Sydney Morning Herald. 13 November 2008. Retrieved 26 December 2009.33. ^ a b ASHRAE. "Ice Manufacture". 2006 ASHRAE Handbook: Refrigeration. Inch-Pound Edition. p. 34-1. ISBN 1-

931862-86-9.34. ^ Rydzewski, A.J. "Mechanical Refrigeration: Ice Making." Marks' Standard Handbook for Mechanical Engineers. 11th

ed. McGraw Hill: New York. pp. 1924. ISBN 978-0-07-142867-5.35. ^ U.S. Census Bureau. "Ice manufacturing: 2002." (http://www.census.gov/prod/ec02/ec0231i312113.pdf) 2002

Economic Census.

36. ^ Deuster, Patricia A.; Singh, Anita; Pelletier, Pierre A. (2007). The U.S. Navy Seal Guide to Fitness and Nutrition(http://books.google.com/books?id=3P038jE18BwC&pg=PT117). Skyhorse Publishing Inc. p. 117. ISBN 1-60239-030-4.

37. ^ "Unique ice pier provides harbor for ships," (http://antarcticsun.usap.gov/pastIssues/2005-2006/2006_01_08.pdf#page=3) Antarctic Sun. 8 January 2006; McMurdo Station, Antarctica.

38. ^ Wildwood Survival Fire From Ice Rob Bicevskis(http://wildwoodsurvival.com/survival/fire/ice/rb/rbfirefromice3a.html). Wildwoodsurvival.com. Retrieved on 30 October2011.

39. ^ Talkington, Fiona (3 May 2005). "Terje Isungset Iceman Is Review" (http://www.bbc.co.uk/music/reviews/cj63). BBCMusic. Retrieved 24 May 2011.

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External links

The National Snow and Ice Data Center (http://nsidc.org/), based in the United StatesThe phase diagram of water, including the ice variants(http://www.its.caltech.edu/~atomic/snowcrystals/ice/ice.htm)Webmineral listing for Ice (http://www.webmineral.com/data/Ice.shtml)MinDat.org listing and location data for Ice (http://www.mindat.org/min-2001.html)The physics of ice (http://www-2.cs.cmu.edu/~dst/ATG/ice.html)The phase diagrams of water with some high pressure diagrams (http://www.lsbu.ac.uk/water/phase.html)'Unfreezable' water, 'bound water' and water of hydration(http://www.phys.unsw.edu.au/~jw/unfreezable.html)Electromechanical properties of ice

(http://adsabs.harvard.edu/abs/2006Natur.439..183I). doi:10.1038/nature04415(http://dx.doi.org/10.1038%2Fnature04415). PMID 16407948 (//www.ncbi.nlm.nih.gov/pubmed/16407948).

42. ^ Salzmann, C.G.; et al. (2006). "The Preparation and Structures of Hydrogen Ordered Phases of Ice". Science 311(5768): 17581761. Bibcode:2006Sci...311.1758S (http://adsabs.harvard.edu/abs/2006Sci...311.1758S).doi:10.1126/science.1123896 (http://dx.doi.org/10.1126%2Fscience.1123896). PMID 16556840(//www.ncbi.nlm.nih.gov/pubmed/16556840).

43. ^ Sanders, Laurua (11 September 2009). "A Very Special Snowball"(http://www.sciencenews.org/view/generic/id/47258/title/A_very_special_snowball). Science News. Retrieved 11September 2009.

44. ^ Militzer, B. and Wilson, H. F. (2010). "New Phases of Water Ice Predicted at Megabar Pressures"(http://militzer.berkeley.edu/papers/ice26.pdf). Physical Review Letters 105 (19): 195701. arXiv:1009.4722(//arxiv.org/abs/1009.4722). Bibcode:2010PhRvL.105s5701M (http://adsabs.harvard.edu/abs/2010PhRvL.105s5701M).doi:10.1103/PhysRevLett.105.195701 (http://dx.doi.org/10.1103%2FPhysRevLett.105.195701). PMID 21231184(//www.ncbi.nlm.nih.gov/pubmed/21231184).

45. ^ MacMahon, J. M. (1970). "Ground-State Structures of Ice at High-Pressures" (http://arxiv.org/pdf/1106.1941.pdf).Physical Review B 84 (22). arXiv:1106.1941 (//arxiv.org/abs/1106.1941). Bibcode:2011arXiv1106.1941M(http://adsabs.harvard.edu/abs/2011arXiv1106.1941M). doi:10.1103/PhysRevB.84.220104(http://dx.doi.org/10.1103%2FPhysRevB.84.220104).

46. ^ Chang, Kenneth (9 December 2004). "Astronomers Contemplate Icy Volcanoes in Far Places"(http://www.nytimes.com/2004/12/09/science/09ice.html). New York Times. Retrieved 30 July 2012.

47. ^ Murray, Benjamin J.; Bertram, Allan K. (2006). "Formation and stability of cubic ice in water droplets"(https://circle.ubc.ca/bitstream/id/118348/Bertram_2006_CPPC_b513480c.pdf). Physical Chemistry Chemical Physics 8(1): 186192. Bibcode:2006PCCP....8..186M (http://adsabs.harvard.edu/abs/2006PCCP....8..186M).doi:10.1039/b513480c (http://dx.doi.org/10.1039%2Fb513480c). PMID 16482260(//www.ncbi.nlm.nih.gov/pubmed/16482260).

48. ^ Murray, Benjamin J. (2008). "The Enhanced formation of cubic ice in aqueous organic acid droplets"(http://media.cigionline.org/geoeng/2008%20-%20Murray%20-%20Enhanced%20formation%20of%20cubic%20ice%20in%20aqueous%20organic%20acid%20droplets.pdf).Environmental Research Letters 3 (2): 025008. Bibcode:2008ERL.....3b5008M(http://adsabs.harvard.edu/abs/2008ERL.....3b5008M). doi:10.1088/1748-9326/3/2/025008(http://dx.doi.org/10.1088%2F1748-9326%2F3%2F2%2F025008).

49. ^ Murray, Benjamin J.; Knopf, Daniel A.; Bertram, Allan K. (2005). "The formation of cubic ice under conditionsrelevant to Earth's atmosphere". Nature 434 (7030): 202205. Bibcode:2005Natur.434..202M(http://adsabs.harvard.edu/abs/2005Natur.434..202M). doi:10.1038/nature03403(http://dx.doi.org/10.1038%2Fnature03403). PMID 15758996 (//www.ncbi.nlm.nih.gov/pubmed/15758996).

50. ^ Chaplin, Martin (10 April 2012). "Ice-four (Ice IV)" (http://www.lsbu.ac.uk/water/ice_iv.html). Water Structure andScience. London South Bank University. Retrieved 30 July 2012.

51. ^ Chaplin, Martin (10 April 2012). "Ice-five (Ice V)" (http://www.lsbu.ac.uk/water/ice_v.html). Water Structure andScience. London South Bank University. Retrieved 30 July 2012.

52. ^ Chaplin, Martin (10 April 2012). "Ice-six (Ice VI)" (http://www.lsbu.ac.uk/water/ice_vi.html). Water Structure andScience. London South Bank University. Retrieved 30 July 2012.

53. ^ Chaplin, Martin (10 April 2012). "Ice-seven (Ice VII)" (http://www.lsbu.ac.uk/water/ice_vii.html). Water Structure andScience. London South Bank University. Retrieved 30 July 2012.

54. ^ Chaplin, Martin (10 April 2012). "Hexagonal Ice (Ice Ih)" (http://www.lsbu.ac.uk/water/ice1h.html#icexi). WaterStructure and Science. London South Bank University. Retrieved 30 July 2012.

55. ^ a b Chaplin, Martin (10 April 2012). "Ice-twelve (Ice XII)" (http://www.lsbu.ac.uk/water/ice_xii.html). Water Structureand Science. London South Bank University. Retrieved 30 July 2012.

(http://permanent.access.gpo.gov/websites/armymil/www.crrel.usace.army.mil/techpub/CRREL_Reports/reports/sr96_02.pdf)Estimating the maximum thickness of an ice layer (http://www.sciencebits.com/StandingOnIce)Sandia's Z machine creates ice in nanoseconds (http://www.physorg.com/news93200439.html)Amazing ice at Lac Leman (http://yak.photo.neuf.fr/001/thematic/ice/pages/P1300303.html)The Surprisingly Cool History of Ice (http://blogs.static.mentalfloss.com/blogs/archives/20311.html)

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