The phases of ice are all possible states of matter for water as a solid. Variations in pressure and temperature give rise to different phases, which have varying properties and molecular geometries. Currently, twenty one phases, including both crystalline and amorphous ices have been observed. In modern history, phases have been discovered through scientific research with various techniques including pressurization, force application, nucleation agents, and others.
115-713: An icicle is a spike of ice formed when water falling from an object freezes . Icicles can form during bright, sunny, but subfreezing weather, when ice or snow melted by sunlight or some other heat source (such as a poorly insulated building), refreezes as it drips off under exposed conditions. Over time continued water runoff will cause the icicle to grow. Another set of conditions is during ice storms , when rain falling in air slightly below freezing slowly accumulates as numerous small icicles hanging from twigs, leaves, wires, etc. Thirdly, icicles can form wherever water seeps out of or drips off vertical surfaces such as road cuts or cliffs. Under some conditions these can slowly form
230-619: A density between a quarter and two thirds that of pure ice, due to a high proportion of trapped air, which also makes soft rime appear white. Hard rime is denser, more transparent, and more likely to appear on ships and aircraft. Cold wind specifically causes what is known as advection frost when it collides with objects. When it occurs on plants, it often causes damage to them. Various methods exist to protect agricultural crops from frost - from simply covering them to using wind machines. In recent decades, irrigation sprinklers have been calibrated to spray just enough water to preemptively create
345-410: A few molecules in the droplet need to get together by chance to form an arrangement similar to that in an ice lattice; then the droplet freezes around this "nucleus". Experiments show that this "homogeneous" nucleation of cloud droplets only occurs at temperatures lower than −35 °C (238 K; −31 °F). In warmer clouds an aerosol particle or "ice nucleus" must be present in (or in contact with)
460-704: A form of precipitation consisting of small, translucent balls of ice, which are usually smaller than hailstones. This form of precipitation is also referred to as "sleet" by the United States National Weather Service . (In British English "sleet" refers to a mixture of rain and snow .) Ice pellets typically form alongside freezing rain, when a wet warm front ends up between colder and drier atmospheric layers. There, raindrops would both freeze and shrink in size due to evaporative cooling. So-called snow pellets, or graupel , form when multiple water droplets freeze onto snowflakes until
575-559: A function of temperature and sliding speed. 2014 research suggests that frictional heating is the most important process under most typical conditions. The term that collectively describes all of the parts of the Earth's surface where water is in frozen form is the cryosphere . Ice is an important component of the global climate, particularly in regard to the water cycle. Glaciers and snowpacks are an important storage mechanism for fresh water; over time, they may sublimate or melt. Snowmelt
690-432: A hailstone becomes too heavy to be supported by the storm's updraft, it falls from the cloud. Hail forms in strong thunderstorm clouds, particularly those with intense updrafts, high liquid water content, great vertical extent, large water droplets, and where a good portion of the cloud layer is below freezing 0 °C (32 °F). Hail-producing clouds are often identifiable by their green coloration. The growth rate
805-581: A key role in Earth's water cycle and climate . In the recent decades, ice volume on Earth has been decreasing due to climate change . The largest declines have occurred in the Arctic and in the mountains located outside of the polar regions. The loss of grounded ice (as opposed to floating sea ice ) is the primary contributor to sea level rise . Humans have been using ice for various purposes for thousands of years. Some historic structures designed to hold ice to provide cooling are over 2,000 years old. Before
920-419: A layer of ice that would form slowly and so avoid a sudden temperature shock to the plant, and not be so thick as to cause damage with its weight. Ablation of ice refers to both its melting and its dissolution . The melting of ice entails the breaking of hydrogen bonds between the water molecules. The ordering of the molecules in the solid breaks down to a less ordered state and the solid melts to become
1035-602: A liquid such as propane around 80 K, or by hyperquenching fine micrometer -sized droplets on a sample-holder kept at liquid nitrogen temperature, 77 K, in a vacuum. Cooling rates above 10 K/s are required to prevent crystallization of the droplets. At liquid nitrogen temperature, 77 K, HGW is kinetically stable and can be stored for many years. Amorphous ices have the property of suppressing long-range density fluctuations and are, therefore, nearly hyperuniform . Classification analysis suggests that low and high density amorphous ices are glasses . Ice from
1150-456: A liquid. This is achieved by increasing the internal energy of the ice beyond the melting point . When ice melts it absorbs as much energy as would be required to heat an equivalent amount of water by 80 °C. While melting, the temperature of the ice surface remains constant at 0 °C. The rate of the melting process depends on the efficiency of the energy exchange process. An ice surface in fresh water melts solely by free convection with
1265-436: A low speed. 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. 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
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#17327805853231380-514: A phase transition had taken place, and Onsager pointed out that the peak could also arise from the movement of defects and lattice imperfections. Onsager suggested that experimentalists look for a dramatic change in heat capacity by performing a careful calorimetric experiment. A phase transition to ice XI was first identified experimentally in 1972 by Shuji Kawada and others. Water molecules in ice I h are surrounded by four semi-randomly directed hydrogen bonds. Such arrangements should change to
1495-431: A proton-ordered form. The total internal energy of ice XI c was predicted as similar as ice XI h . Ice XI is ferroelectric , meaning that it has an intrinsic polarization. To qualify as a ferroelectric it must also exhibit polarization switching under an electric field, which has not been conclusively demonstrated but which is implicitly assumed to be possible. Cubic ice also has a ferrolectric phase and in this case
1610-505: A rate that depends linearly on the water temperature, T ∞ , when T ∞ is less than 3.98 °C, and superlinearly when T ∞ is equal to or greater than 3.98 °C, with the rate being proportional to (T ∞ − 3.98 °C) , with α = 5 / 3 for T ∞ much greater than 8 °C, and α = 4 / 3 for in between temperatures T ∞ . In salty ambient conditions, dissolution rather than melting often causes
1725-1438: A refined result of R ln ( 1.5 × ( 730 / 729 ) 2 ) = R ln ( 1.504 ) {\displaystyle R\ln(1.5\times (730/729)^{2})=R\ln(1.504)} . These phases are named according to the Bridgman nomenclature. The majority have only been created in the laboratory at different temperatures and pressures. 240 K (−33 °C) (conversion to Ice I h ) <30 K (−243.2 °C) (vapor deposition); 77 K (−196.2 °C) (stability point) 77 K (−196.2 °C) (stability point) 77 K (−196.2 °C) (stability point) 77 K (−196.2 °C) (stability point) 77 K (−196.2 °C) (stability point) 130 K (−143 °C) - 355 K (82 °C) (stability range) <140 K (−133 °C) (stability point) <140 K (−133 °C) (stability point) 77 K (−196.2 °C) (formation from ice I h ); 183 K (−90 °C) (formation from HDA ice) <140 K (−133 °C) (stability point) <140 K (−133 °C) (stability point) The properties of ice II were first described and recorded by Gustav Heinrich Johann Apollon Tammann in 1900 during his experiments with ice under high pressure and low temperatures. Having produced ice III, Tammann then tried condensing
1840-487: A single oxygen atom covalently bonded to two hydrogen atoms , or H–O–H. However, many of the physical properties of water and ice are controlled by the formation of hydrogen bonds between adjacent oxygen and hydrogen atoms; while it is a weak bond, it is nonetheless critical in controlling the structure of both water and ice. An unusual property of water is that its solid form—ice frozen at atmospheric pressure —is approximately 8.3% less dense than its liquid form; this
1955-746: A soft ball-like shape is formed. So-called " diamond dust ", (METAR code IC ) 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. As water drips and re-freezes, it can form hanging icicles , or stalagmite -like structures on the ground. On sloped roofs, buildup of ice can produce an ice dam , which stops melt water from draining properly and potentially leads to damaging leaks. More generally, water vapor depositing onto surfaces due to high relative humidity and then freezing results in various forms of atmospheric icing , or frost . Inside buildings, this can be seen as ice on
2070-471: A temperature of −78.5 °C (−109.3 °F), the vaporization point of solid carbon dioxide (dry ice). 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 (32 °F). Ice, water, and water vapour can coexist at
2185-536: A theorized superionic water may possess two crystalline structures. At pressures in excess of 50 GPa (7,300,000 psi) such superionic ice would take on a body-centered cubic structure. However, at pressures in excess of 100 GPa (15,000,000 psi) the structure may shift to a more stable face-centered cubic lattice. Some estimates suggest that at an extremely high pressure of around 1.55 TPa (225,000,000 psi), ice would develop metallic properties. Ice, water, and water vapour can coexist at
2300-574: A thin surface layer, which makes it particularly hazardous to walk across it. Another dangerous form of rotten ice to traverse on foot is candle ice, which develops in columns perpendicular to the surface of a lake. Because it lacks a firm horizontal structure, a person who has fallen through has nothing to hold onto to pull themselves out. Snow crystals form when tiny supercooled cloud droplets (about 10 μm in diameter) freeze . These droplets are able to remain liquid at temperatures lower than −18 °C (255 K; 0 °F), because to freeze,
2415-658: A way that still makes sure each oxygen atom is bond to two hydrogen atoms. The oxygen atoms can be divided into two sets in a checkerboard pattern, shown in the picture as black and white balls. Focus attention on the oxygen atoms in one set: there are N /2 of them. Each has four hydrogen bonds, with two hydrogens close to it and two far away. This means there are ( 4 2 ) = 6 {\textstyle {\tbinom {4}{2}}=6} allowed configurations of hydrogens for this oxygen atom (see Binomial coefficient ). Thus, there are 6 configurations that satisfy these N /2 atoms. But now, consider
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#17327805853232530-431: Is 5987 J/mol , and its latent heat of sublimation is 50 911 J/mol . The high latent heat of sublimation is principally indicative of the strength of the hydrogen bonds in the crystal lattice. The latent heat of melting is much smaller, partly because liquid water near 0 °C also contains a significant number of hydrogen bonds. By contrast, the structure of ice II is hydrogen-ordered, which helps to explain
2645-533: Is 'naive', as it assumes the six out of 16 hydrogen configurations for oxygen atoms in the second set can be independently chosen, which is false. More complex methods can be employed to better approximate the exact number of possible configurations, and achieve results closer to measured values. Nagle (1966) used a series summation to obtain R ln ( 1.50685 ± 0.00015 ) {\displaystyle R\ln(1.50685\pm 0.00015)} . As an illustrative example of refinement, consider
2760-442: Is a basic cause of freeze-thaw weathering of rock in nature and damage to building foundations and roadways from frost heaving . It is also a common cause of the flooding of houses when water pipes burst due to the pressure of expanding water when it freezes. Because ice is less dense than liquid water, it floats, and this prevents bottom-up freezing of the bodies of water. Instead, a sheltered environment for animal and plant life
2875-417: Is about 275 pm and is the same between any two bonded oxygen atoms in the lattice. The angle between bonds in the crystal lattice is very close to the tetrahedral angle of 109.5°, which is also quite close to the angle between hydrogen atoms in the water molecule (in the gas phase), which is 105°. This tetrahedral bonding angle of the water molecule essentially accounts for the unusually low density of
2990-427: Is abundant on the Earth's surface, particularly in the polar regions and above the snow line , where it can aggregate from snow to form glaciers and ice sheets . As snowflakes and hail , ice is a common form of precipitation , and it may also be deposited directly by water vapor as frost . The transition from ice to water is melting and from ice directly to water vapor is sublimation . These processes plays
3105-426: Is an amorphous solid form of water, which lacks long-range order in its molecular arrangement. Amorphous ice is produced either by rapid cooling of liquid water to its glass transition temperature (about 136 K or −137 °C) in milliseconds (so the molecules do not have enough time to form a crystal lattice ), or by compressing ordinary ice at low temperatures. The most common form on Earth, low-density ice,
3220-424: Is an important source of seasonal fresh water. The World Meteorological Organization defines several kinds of ice depending on origin, size, shape, influence and so on. Clathrate hydrates are forms of ice that contain gas molecules trapped within its crystal lattice. 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 ice if attached to
3335-456: Is below them. In addition, ice deposits can be heavy. If enough icicles form on an object, such as a wire, beam, or pole, the weight of the ice can severely damage the structural integrity of the object and may cause the object to break. This can also happen with roofs, where failure can damage nearby parked vehicles or the contents and occupants of the structure. Icicles on roofs can also be associated with ice dams , which can cause water damage as
3450-480: Is completely hydrogen ordered, the presence of its disordered counterpart is a great matter of interest. Shephard et al. investigated the phase boundaries of NH 4 F-doped ices because NH 4 F has been reported to be a hydrogen disordering reagent. However, adding 2.5 mol% of NH 4 F resulted in the disappearance of ice II instead of the formation of a disordered ice II. According to the DFC calculation by Nakamura et al.,
3565-432: Is compressed, released and then heated, it releases a large amount of heat energy, unlike other water ices which return to their normal form after getting similar treatment. The hydrogen atoms in the crystal lattice lie very nearly along the hydrogen bonds, and in such a way that each water molecule is preserved. This means that each oxygen atom in the lattice has two hydrogens adjacent to it: at about 101 pm along
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3680-498: Is cooled below 0 °C ( 273.15 K , 32 °F ) at standard atmospheric pressure . When water is cooled rapidly ( quenching ), up to three types of amorphous ice can form. Interstellar ice is overwhelmingly low-density amorphous ice (LDA), which likely makes LDA ice the most abundant type in the universe. When cooled slowly, correlated proton tunneling occurs below −253.15 °C ( 20 K , −423.67 °F ) giving rise to macroscopic quantum phenomena . Ice
3795-436: Is cooled to below 72 K . The low temperature required to achieve this transition is correlated with the relatively low energy difference between the two structures. Hints of hydrogen-ordering in ice had been observed as early as 1964, when Dengel et al. attributed a peak in thermo-stimulated depolarization (TSD) current to the existence of a proton-ordered ferroelectric phase. However, they could not conclusively prove that
3910-494: Is divided into four categories: pore ice, vein ice (also known as ice wedges), buried surface ice and intrasedimental ice (from the freezing of underground waters). One example of ice formation in permafrost areas is aufeis - 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
4025-435: Is equivalent to a volumetric expansion of 9%. The density of ice is 0.9167 –0.9168 g/cm at 0 °C and standard atmospheric pressure (101,325 Pa), whereas water has a density of 0.9998 –0.999863 g/cm at the same temperature and pressure. Liquid water is densest, essentially 1.00 g/cm , at 4 °C and begins to lose its density as the water molecules begin to form the hexagonal crystals of ice as
4140-484: Is extremely rare otherwise. Even icy moons like Ganymede are expected to mainly consist of other crystalline forms of ice. 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)
4255-484: Is formed beneath the floating ice, which protects the underside from short-term weather extremes such as wind chill . Sufficiently thin floating ice allows light to pass through, supporting the photosynthesis of bacterial and algal colonies. When sea water freezes, the ice is riddled with brine-filled channels which sustain sympagic organisms such as bacteria, algae, copepods and annelids . In turn, they provide food for animals such as krill and specialized fish like
4370-452: Is formed by compression of ordinary ice I h or LDA at GPa pressures. Very-high-density ASW (VHDA) is HDA slightly warmed to 160 K under 1–2 GPa pressures. Ice from a theorized superionic water may possess two crystalline structures. At pressures in excess of 500,000 bars (7,300,000 psi) such superionic ice would take on a body-centered cubic structure. However, at pressures in excess of 1,000,000 bars (15,000,000 psi)
4485-536: Is found in the hexagonal Ice I h phase. Less common phases may be found in the atmosphere and underground due to more extreme pressures and temperatures. Some phases are manufactured by humans for nano scale uses due to their properties. In space, amorphous ice is the most common form as confirmed by observation. Thus, it is theorized to be the most common phase in the universe. Various other phases could be found naturally in astronomical objects. Most liquids under increased pressure freeze at higher temperatures because
4600-448: Is maximized at about −13 °C (9 °F), and becomes vanishingly small much below −30 °C (−22 °F) as supercooled water droplets become rare. For this reason, hail is most common within continental interiors of the mid-latitudes, as hail formation is considerably more likely when the freezing level is below the altitude of 11,000 feet (3,400 m). Entrainment of dry air into strong thunderstorms over continents can increase
4715-474: Is necessary to add small amounts of KOH catalyst.) It forms (ordered) ice VIII below 273 K up to ~8 GPa. Above this pressure, the VII–VIII transition temperature drops rapidly, reaching 0 K at ~60 GPa. Thus, ice VII has the largest stability field of all of the molecular phases of ice. The cubic oxygen sub-lattices that form the backbone of the ice VII structure persist to pressures of at least 128 GPa; this pressure
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4830-464: Is over 70% ice on its surface is said to be covered by pack ice. Fully formed sea ice can be forced together by currents and winds to form pressure ridges up to 12 metres (39 ft) tall. On the other hand, active wave activity can reduce sea ice to small, regularly shaped pieces, known as pancake ice . Sometimes, wind and wave activity "polishes" sea ice to perfectly spherical pieces known as ice eggs . The largest ice formations on Earth are
4945-409: Is shifted toward slightly lower energies. Thus, ice appears blue, with a slightly greener tint than liquid water. Since absorption is cumulative, the color effect intensifies with increasing thickness or if internal reflections cause the light to take a longer path through the ice. Other colors can appear in the presence of light absorbing impurities, where the impurity is dictating the color rather than
5060-472: Is substantially higher than that at which water loses its molecular character entirely, forming ice X. In high pressure ices, protonic diffusion (movement of protons around the oxygen lattice) dominates molecular diffusion, an effect which has been measured directly. Ice XI is the hydrogen-ordered form of the ordinary form of ice. The total internal energy of ice XI is about one sixth lower than ice I h , so in principle it should naturally form when ice I h
5175-529: Is the Boltzmann constant and R is the molar gas constant . So, the molar residual entropy is R ln ( 3 / 2 ) = 3.37 J ⋅ m o l − 1 K − 1 {\displaystyle R\ln(3/2)=3.37\mathrm {J} \cdot \mathrm {mol} ^{-1}\mathrm {K} ^{-1}} . The same answer can be found in another way. First orient each water molecule randomly in each of
5290-413: Is the one used by Linus Pauling . Suppose there are a given number N of water molecules in an ice lattice. To compute its residual entropy, we need to count the number of configurations that the lattice can assume. The oxygen atoms are fixed at the lattice points, but the hydrogen atoms are located on the lattice edges. The problem is to pick one end of each lattice edge for the hydrogen to bond to, in
5405-531: Is therefore slower than melting. Ice has long been valued as a means of cooling. In 400 BC Iran, Persian engineers had already developed techniques for ice storage in the desert through the summer months. During the winter, ice was transported from harvesting pools and nearby mountains in large quantities to be stored in specially designed, naturally cooled refrigerators , called yakhchal (meaning ice storage ). Yakhchals were large underground spaces (up to 5000 m ) that had thick walls (at least two meters at
5520-402: Is usually formed in the laboratory by a slow accumulation of water vapor molecules ( physical vapor deposition ) onto a very smooth metal crystal surface under 120 K. In outer space it is expected to be formed in a similar manner on a variety of cold substrates, such as dust particles. By contrast, hyperquenched glassy water (HGW) is formed by spraying a fine mist of water droplets into
5635-534: The National Library of Russia . Ice Ice is water that is frozen into a solid state, typically forming at or below temperatures of 0 ° C , 32 ° F , or 273.15 K . It occurs naturally on Earth , on other planets, in Oort cloud objects, and as interstellar ice . As a naturally occurring crystalline inorganic solid with an ordered structure, ice is considered to be a mineral . Depending on
5750-446: The bald notothen , fed upon in turn by larger animals such as emperor penguins and minke whales . When ice melts, it absorbs as much energy as it would take to heat an equivalent mass of water by 80 °C (176 °F). During the melting process, the temperature remains constant at 0 °C (32 °F). While melting, any energy added breaks the hydrogen bonds between ice (water) molecules. Energy becomes available to increase
5865-755: The triple point , which is exactly 273.16 K (0.01 °C) at a pressure of 611.657 Pa . The kelvin was defined as 1 / 273.16 of the difference between this triple point and absolute zero , though this definition changed in May 2019. 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 . Subjected to higher pressures and varying temperatures, ice can form in nineteen separate known crystalline phases at various densities, along with hypothetical proposed phases of ice that have not been observed. With care, at least fifteen of these phases (one of
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#17327805853235980-468: The triple point , which is exactly 273.16 K (0.01 °C) at a pressure of 611.657 Pa . The kelvin was defined as 1 / 273.16 of the difference between this triple point and absolute zero , though this definition changed in May 2019. 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 . The latent heat of melting
6095-473: The "Ice King", worked on developing better insulation products for long distance shipments of ice, especially to the tropics; this became known as the ice trade. Between 1812 and 1822, under Lloyd Hesketh Bamford Hesketh 's instruction, Gwrych Castle was built with 18 large towers, one of those towers is called the 'Ice Tower'. Its sole purpose was to store Ice. Trieste sent ice to Egypt , Corfu , and Zante ; Switzerland, to France; and Germany sometimes
6210-418: The "frozen waterfalls" favored by ice climbers . Icicles form on surfaces which might have a smooth and straight, or irregular shape, which in turn influences the shape of an icicle. Another influence is melting water, which might flow toward the icicle in a straight line or which might flow from several directions. Impurities in the water can lead to ripples on the surface of the icicles. Icicles elongate by
6325-414: The 275 pm length of the bond for ice Ih. The crystal lattice allows a substantial amount of disorder in the positions of the hydrogen atoms frozen into the structure as it cools to absolute zero. As a result, the crystal structure contains some residual entropy inherent to the lattice and determined by the number of possible configurations of hydrogen positions that can be formed while still maintaining
6440-534: The 6 possible configurations, then check that each lattice edge contains exactly one hydrogen atom. Assuming that the lattice edges are independent, then the probability that a single edge contains exactly one hydrogen atom is 1/2, and since there are 2N edges in total, we obtain a total configuration count 6 N × ( 1 / 2 ) 2 N = ( 3 / 2 ) N {\displaystyle 6^{N}\times (1/2)^{2N}=(3/2)^{N}} , as before. This estimate
6555-624: The United States, with a combined value of shipments of $ 595,487,000. Home refrigerators can also make ice with a built in icemaker , which will typically make ice cubes or crushed ice. The first such device was presented in 1965 by Frigidaire . Ice forming on roads is a common winter hazard, and black ice particularly dangerous because it is very difficult to see. It is both very transparent, and often forms specifically in shaded (and therefore cooler and darker) areas, i.e. beneath overpasses . Phases of ice On Earth, most ice
6670-475: The ablation of ice. For example, the temperature of the Arctic Ocean is generally below the melting point of ablating sea ice. The phase transition from solid to liquid is achieved by mixing salt and water molecules, similar to the dissolution of sugar in water, even though the water temperature is far below the melting point of the sugar. However, the dissolution rate is limited by salt concentration and
6785-419: The base) made of a specific type of mortar called sarooj made from sand, clay, egg whites, lime, goat hair, and ash. The mortar was resistant to heat transfer, helping to keep the ice cool enough not to melt; it was also impenetrable by water. Yakhchals often included a qanat and a system of windcatchers that could lower internal temperatures to frigid levels, even during the heat of the summer. One use for
6900-405: The change in conformation back to ice I h . In later experiments by Bridgman in 1912, it was shown that the difference in volume between ice II and ice III was in the range of 0.0001 m /kg (2.8 cu in/lb). This difference hadn't been discovered by Tammann due to the small change and was why he had been unable to determine an equilibrium curve between the two. The curve showed that
7015-404: The compression-induced conversion of ice I into ice IV is important, naming it "Engelhardt–Kamb collapse" (EKC). They suggested that the reason why we cannot obtain ice IV directly from ice Ih is that ice Ih is hydrogen-disordered; if oxygen atoms are arranged in the ice IV structure, hydrogen bonding may not be formed due to the donor-acceptor mismatch. and Raman The disordered nature of Ice IV
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#17327805853237130-447: The crystal lattice – it is beneficial for the lattice to be arranged with tetrahedral angles even though there is an energy penalty in the increased volume of the crystal lattice. As a result, the large hexagonal rings leave almost enough room for another water molecule to exist inside. This gives naturally occurring ice its rare property of being less dense than its liquid form. The tetrahedral-angled hydrogen-bonded hexagonal rings are also
7245-427: The droplet to act as a nucleus. Our understanding of what particles make efficient ice nuclei is poor – what we do know is they are very rare compared to that cloud condensation nuclei on which liquid droplets form. Clays, desert dust and biological particles may be effective, although to what extent is unclear. Artificial nuclei are used in cloud seeding . The droplet then grows by condensation of water vapor onto
7360-438: The endothermic feature becomes larger as the sample is quench-recovered at higher pressure. They proposed three scenarios to explain the experimental results: weak hydrogen-ordering, orientational glass transition, and mechanical distortions. Ice VII is the only disordered phase of ice that can be ordered by simple cooling. (While ice I h theoretically transforms into proton-ordered ice XI on geologic timescales, in practice it
7475-476: The endothermic feature becomes larger as the sample is quench-recovered at higher pressure. They proposed three scenarios to explain the experimental results: weak hydrogen-ordering, orientational glass transition, and mechanical distortions. reported the DSC thermograms of HCl-doped ice IV finding an endothermic feature at about 120 K. Ten years later, Rosu-Finsen and Salzmann (2021) reported more detailed DSC data where
7590-443: The entropy change of 3.22 J/mol when the crystal structure changes to that of ice I. Also, ice XI, an orthorhombic, hydrogen-ordered form of ice I h , is considered the most stable form at low temperatures. The transition entropy from ice XIV to ice XII is estimated to be 60% of Pauling entropy based on DSC measurements. The formation of ice XIV from ice XII is more favoured at high pressure. When medium-density amorphous ice
7705-444: The ferroelectric properties of the ice have been experimentally demonstrated on monolayer thin films. In a similar experiment, ferroelectric layers of hexagonal ice were grown on a platinum (111) surface. The material had a polarization that had a decay length of 30 monolayers suggesting that thin layers of ice XI can be grown on substrates at low temperature without the use of dopants. One-dimensional nano-confined ferroelectric ice XI
7820-541: The following way to refine the second estimation method given above. According to it, six water molecules in a hexagonal ring would allow 6 6 × ( 1 / 2 ) 6 = 729 {\displaystyle 6^{6}\times (1/2)^{6}=729} configurations. However, by explicit enumeration, there are actually 730 configurations. Now in the lattice, each oxygen atom participates in 12 hexagonal rings, so there are 2N rings in total for N oxygen atoms, or 2 rings for each oxygen atom, giving
7935-449: 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. The density of ice increases slightly with decreasing temperature and has a value of 0.9340 g/cm at −180 °C (93 K). When water freezes, it increases in volume (about 9% for fresh water). The effect of expansion during freezing can be dramatic, and ice expansion
8050-465: The frequency of hail by promoting evaporative cooling 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-latitudes because the atmosphere over the tropics tends to be warmer over a much greater depth. Hail in the tropics occurs mainly at higher elevations. Ice pellets ( METAR code PL ) are
8165-534: 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. Snow line and snow fields are two related concepts, in that snow fields accumulate on top of and ablate away to the equilibrium point (the snow line) in an ice deposit. Ice which forms on moving water tends to be less uniform and stable than ice which forms on calm water. Ice jams (sometimes called "ice dams"), when broken chunks of ice pile up, are
8280-636: The greatest ice hazard on rivers. Ice jams can cause flooding, damage structures in or near the river, and damage vessels on the river. Ice jams can cause some hydropower industrial facilities to completely shut down. An ice dam is a 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 vessel to keep navigation possible. Ice discs are circular formations of ice floating on river water. They form within eddy currents , and their position results in asymmetric melting, which makes them continuously rotate at
8395-546: The growth of ice as a tube into the pendant drop. The wall of this ice tube is about 0.1 mm (0.004 in) and the width 5 mm (0.2 in). As a result of this growth process, the interior of a growing icicle is liquid water. The growth of an icicle both in length and in width can be calculated and is a complicated function of air temperature, wind speed, and the water flux into the icicle. The growth rate in length typically varies with time, and can in ideal conditions be more than 1 cm (0.39 in) per minute. Given
8510-503: The hailstones to the upper part of the cloud. The updraft dissipates and the hailstones fall down, back into the updraft, and are lifted up again. Hail has a diameter of 5 millimetres (0.20 in) or more. Within METAR code, GR is used to indicate larger hail, of a diameter of at least 6.4 millimetres (0.25 in) and GS for smaller. Stones of 19 millimetres (0.75 in), 25 millimetres (1.0 in) and 44 millimetres (1.75 in) are
8625-407: The ice at a temperature between −70 and −80 °C (203 and 193 K; −94 and −112 °F) under 200 MPa (2,000 atm) of pressure. Tammann noted that in this state ice II was denser than he had observed ice III to be. He also found that both types of ice can be kept at normal atmospheric pressure in a stable condition so long as the temperature is kept at that of liquid air , which slows
8740-464: The ice exerted by any object. However, the significance of this hypothesis is disputed by experiments showing a high coefficient of friction for ice using atomic force microscopy . Thus, the mechanism controlling the frictional properties of ice is still an active area of scientific study. A comprehensive theory of ice friction must take into account all of the aforementioned mechanisms to estimate friction coefficient of ice against various materials as
8855-429: The ice itself. For instance, icebergs containing impurities (e.g., sediments, algae, air bubbles) can appear brown, grey or green. Because ice in natural environments is usually close to its melting temperature, its hardness shows pronounced temperature variations. At its melting point, ice has a Mohs hardness of 2 or less, but the hardness increases to about 4 at a temperature of −44 °C (−47 °F) and to 6 at
8970-456: The ice layer is caused by friction. However, this theory does not sufficiently explain why ice is slippery when standing still even at below-zero temperatures. Subsequent research suggested that ice molecules at the interface cannot properly bond with the molecules of the mass of ice beneath (and thus are free to move like molecules of liquid water). These molecules remain in a semi-liquid state, providing lubrication regardless of pressure against
9085-471: The ice surfaces. Ice storm is a type of winter storm characterized by freezing rain , which produces a glaze of ice on surfaces, including roads and power lines . In the United States, a quarter of winter weather events produce glaze ice, and utilities need to be prepared to minimize damages. Hail forms in storm clouds when supercooled water droplets freeze on contact with condensation nuclei , such as dust or dirt . The storm's updraft blows
9200-481: The ice was to create chilled treats for royalty. There were thriving industries in 16th–17th century England whereby low-lying areas along the Thames Estuary were flooded during the winter, and ice harvested in carts and stored inter-seasonally in insulated wooden houses as a provision to an icehouse often located in large country houses, and widely used to keep fish fresh when caught in distant waters. This
9315-416: The ice which often settles when loaded with snow. An ice shove occurs when ice movement, caused by ice expansion and/or wind action, occurs to the extent that ice pushes onto the shores of lakes, often displacing sediment that makes up the shoreline. Shelf ice is formed when floating pieces of ice are driven by the wind piling up on the windward shore. This kind of ice may contain large air pockets under
9430-603: The ice, would melt a thin layer, providing sufficient lubrication for the blade to glide across the ice. Yet, 1939 research by Frank P. Bowden and T. P. Hughes found that skaters would experience a lot more friction than they actually do if it were the only explanation. Further, the optimum temperature for figure skating is −5.5 °C (22 °F; 268 K) and −9 °C (16 °F; 264 K) for hockey; yet, according to pressure melting theory, skating below −4 °C (25 °F; 269 K) would be outright impossible. Instead, Bowden and Hughes argued that heating and melting of
9545-427: The invention of refrigeration technology, the only way to safely store food without modifying it through preservatives was to use ice. Sufficiently solid surface ice makes waterways accessible to land transport during winter, and dedicated ice roads may be maintained. Ice also plays a major role in winter sports . Ice possesses a regular crystalline structure based on the molecule of water, which consists of
9660-515: The known exceptions being ice X) can be recovered at ambient pressure and low temperature in metastable form. The types are differentiated by their crystalline structure, proton ordering, and density. There are also two metastable phases of ice under pressure, both fully hydrogen-disordered; these are Ice IV and Ice XII. Ice XII was discovered in 1996. In 2006, Ice XIII and Ice XIV were discovered. Ices XI, XIII, and XIV are hydrogen-ordered forms of ices I h , V, and XII respectively. In 2009, ice XV
9775-495: The large number of glaciers it contains. They cover an area of around 80,000 km (31,000 sq mi), and have a combined volume of between 3,000-4,700 km . These glaciers are nicknamed "Asian water towers", because their meltwater run-off feeds into rivers which provide water for an estimated two billion people. Permafrost refers to soil or underwater sediment which continuously remains below 0 °C (32 °F) for two years or more. The ice within permafrost
9890-405: The mechanism that causes liquid water to be densest at 4 °C. Close to 0 °C, tiny hexagonal ice I h -like lattices form in liquid water, with greater frequency closer to 0 °C. This effect decreases the density of the water, causing it to be densest at 4 °C when the structures form infrequently. In the best-known form of ice, ice I h , the crystal structure is characterized by
10005-415: The more ordered arrangement of hydrogen bonds found in ice XI at low temperatures, so long as localized proton hopping is sufficiently enabled; a process that becomes easier with increasing pressure. Correspondingly, ice XI is believed to have a triple point with hexagonal ice and gaseous water at (~72 K, ~0 Pa). Ice I h that has been transformed to ice XI and then back to ice I h , on raising
10120-524: The most frequently reported hail sizes in North America. Hailstones can grow to 15 centimetres (6 in) and weigh more than 0.5 kilograms (1.1 lb). In large hailstones, latent heat released by further freezing may melt the outer shell of the hailstone. The hailstone then may undergo 'wet growth', where the liquid outer shell collects other smaller hailstones. The hailstone gains an ice layer and grows increasingly larger with each ascent. Once
10235-510: The oxygen atoms forming hexagonal symmetry with near tetrahedral bonding angles. This structure is stable down to −268 °C (5 K; −450 °F), as evidenced by x-ray diffraction and extremely high resolution thermal expansion measurements. Ice I h is also stable under applied pressures of up to about 210 megapascals (2,100 atm) where it transitions into ice III or ice II. While most forms of ice are crystalline, several amorphous (or "vitreous") forms of ice also exist. Such ice
10350-408: The phase boundary between ice II and its disordered counterpart is estimated to be in the stability region of liquid water. 1981 research by Engelhardt and Kamb elucidated crystal structure of ice IV through a low-temperature single-crystal X-ray diffraction, describing it as a rhombohedral unit cell with a space group of R-3c. This research mentioned that the structure of ice IV could be derived from
10465-454: The presence of impurities such as particles of soil or bubbles of air , it can appear transparent or a more or less opaque bluish-white color. Virtually all of the ice on Earth is of a hexagonal crystalline structure denoted as ice I h (spoken as "ice one h"). Depending on temperature and pressure, at least nineteen phases ( packing geometries ) can exist. The most common phase transition to ice I h occurs when liquid water
10580-772: 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. Subjected to higher pressures and varying temperatures, ice can form in nineteen separate known crystalline phases. With care, at least fifteen of these phases (one of the known exceptions being ice X) can be recovered at ambient pressure and low temperature in metastable form. The types are differentiated by their crystalline structure, proton ordering, and density. There are also two metastable phases of ice under pressure, both fully hydrogen-disordered; these are Ice IV and Ice XII. The accepted crystal structure of ordinary ice
10695-514: The process to an even older author, Ibn Bakhtawayhi, of whom nothing is known. 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. Most commercial icemakers produce three basic types of fragmentary ice: flake, tubular and plate, using a variety of techniques. Large batch ice makers can produce up to 75 tons of ice per day. In 2002, there were 426 commercial ice-making companies in
10810-843: The remaining N /2 oxygen atoms: in general they won't be satisfied (i.e., they will not have precisely two hydrogen atoms near them). For each of those, there are 2 = 16 possible placements of the hydrogen atoms along their hydrogen bonds, of which 6 are allowed. So, naively, we would expect the total number of configurations to be 6 N / 2 ( 6 / 16 ) N / 2 = ( 3 / 2 ) N . {\displaystyle 6^{N/2}(6/16)^{N/2}=(3/2)^{N}.} Using Boltzmann's entropy formula , we conclude that S 0 = k ln ( 3 / 2 ) N = n R ln ( 3 / 2 ) , {\displaystyle S_{0}=k\ln(3/2)^{N}=nR\ln(3/2),} where k
10925-457: The requirement for each oxygen atom to have only two hydrogens in closest proximity, and each H-bond joining two oxygen atoms having only one hydrogen atom. This residual entropy S 0 is equal to 3.4±0.1 J mol K = R ln ( 1.50 ± 0.02 ) {\displaystyle =R\ln(1.50\pm 0.02)} . There are various ways of approximating this number from first principles. The following
11040-471: The right conditions, icicles may also form in caves (in which case they are also known as ice stalactites ). They can also form within salty water ( brine ) sinking from sea ice. These so-called brinicles can kill sea urchins and starfish , which was observed by BBC film crews near Mount Erebus , Antarctica. Icicles can pose personal and structural dangers. Icicles that hang from an object may fall and cause injury and/or damage to whoever or whatever
11155-417: The same form. Bridgman found that the equilibrium curve between ice II and ice IV was much the same as with ice III, having the same stability properties and small volume change. The curve between ice II and ice V was extremely different, however, with the curve's bubble being essentially a straight line and the volume difference being almost always 0.000 0545 m /kg (1.51 cu in/lb). As ice II
11270-425: The seafloor. Ice which calves (breaks off) from an ice shelf or a coastal glacier may become an iceberg. The aftermath of calving events produces a loose mixture of snow and ice known as Ice mélange . Sea ice forms in several stages. At first, small, millimeter-scale crystals accumulate on the water surface in what is known as frazil ice . As they become somewhat larger and more consistent in shape and cover,
11385-401: The structural change from ice III to ice II was more likely to happen if the medium had previously been in the structural conformation of ice II. However, if a sample of ice III that had never been in the ice II state was obtained, it could be supercooled even below −70 °C without it changing into ice II. Conversely, however, any superheating of ice II was not possible in regards to retaining
11500-440: The structure may shift to a more stable face-centered cubic lattice. It is speculated that superionic ice could compose the interior of ice giants such as Uranus and Neptune. Ice is " slippery " because it has a low coefficient of friction. This subject was first scientifically investigated in the 19th century. The preferred explanation at the time was " pressure melting " -i.e. the blade of an ice skate, upon exerting pressure on
11615-448: The structure of ice Ic by cutting and forming some hydrogen bondings and adding subtle structural distortions. Shephard et al. compressed the ambient phase of NH 4 F, an isostructural material of ice, to obtain NH 4 F II, whose hydrogen-bonded network is similar to ice IV. As the compression of ice Ih results in the formation of high-density amorphous ice (HDA), not ice IV, they claimed that
11730-705: The summer. The advent of artificial refrigeration technology made the delivery of ice obsolete. Ice is still harvested for ice and snow sculpture events . For example, a swing saw is used to get ice for the Harbin International Ice and Snow Sculpture Festival each year from the frozen surface of the Songhua River . The earliest known written process to artificially make ice is by the 13th-century writings of Arab historian Ibn Abu Usaybia in his book Kitab Uyun al-anba fi tabaqat-al-atibba concerning medicine in which Ibn Abu Usaybia attributes
11845-443: The surface of un-insulated windows. Hoar frost is common in the environment, particularly in the low-lying areas such as valleys . In Antarctica, the temperatures can be so low that electrostatic attraction is increased to the point hoarfrost on snow sticks together when blown by wind into tumbleweed -like balls known as yukimarimo . Sometimes, drops of water crystallize on cold objects as rime instead of glaze. Soft rime has
11960-533: The temperature, retains some hydrogen-ordered domains and more easily transforms back to ice XI again. A neutron powder diffraction study found that small hydrogen-ordered domains can exist up to 111 K. There are distinct differences in the Raman spectra between ices I h and XI, with ice XI showing much stronger peaks in the translational (~230 cm ), librational (~630 cm ) and in-phase asymmetric stretch (~3200 cm ) regions. Ice I c also has
12075-441: The thermal energy (temperature) only after enough hydrogen bonds are broken that the ice can be considered liquid water. The amount of energy consumed 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 an oxygen–hydrogen (O–H) bond stretch. Compared with water, this absorption
12190-486: The two ice sheets which almost completely cover the world's largest island, Greenland , and the continent of Antarctica . These ice sheets have an average thickness of over 1 km (0.6 mi) and have existed for millions of years. Other major ice formations on land include ice caps , ice fields , ice streams and glaciers . In particular, the Hindu Kush region is known as the Earth's "Third Pole" due to
12305-520: The water penetrates below the shingles. The story of an English youth killed by a falling icicle in 1776 has often been recounted. Large icicles that form on cliffs near highways have been known to fall and damage motor vehicles. In 2010, five people were killed and 150 injured by icicles in Saint Petersburg , Russia after heavy snow that also caused apartment block roofs to collapse, as well as creating water damage to private homes and to
12420-433: The water surface begins to look "oily" from above, so this stage is called grease ice . Then, ice continues to clump together, and solidify into flat cohesive pieces known as ice floes . Ice floes are the basic building blocks of sea ice cover, and their horizontal size (defined as half of their diameter ) varies dramatically, with the smallest measured in centimeters and the largest in hundreds of kilometers. An area which
12535-456: Was allegedly copied by an Englishman who had seen the same activity in China. Ice was imported into England from Norway on a considerable scale as early as 1823. In the United States, the first cargo of ice was sent from New York City to Charleston, South Carolina , in 1799, and by the first half of the 19th century, ice harvesting had become a big business. Frederic Tudor , who became known as
12650-417: Was confirmed by neutron powder diffraction studies by Lobban (1998) and Klotz et al. (2003). In addition, the entropy difference between ice VI (disordered phase) and ice IV is very small, according to Bridgman's measurement. Several organic nucleating reagents had been proposed to selectively crystallize ice IV from liquid water, but even with such reagents, the crystallization of ice IV from liquid water
12765-400: Was created in 2010. Although the parent phase ice VI was discovered in 1935, corresponding proton-ordered forms (ice XV) had not been observed until 2009. Theoretically, the proton ordering in ice VI was predicted several times; for example, density functional theory calculations predicted the phase transition temperature is 108 K and the most stable ordered structure is antiferroelectric in
12880-455: Was first proposed by Linus Pauling in 1935. The structure of ice I h is the wurtzite lattice , roughly one of crinkled planes composed of tessellating hexagonal rings, with an oxygen atom on each vertex, and the edges of the rings formed by hydrogen bonds . The planes alternate in an ABAB pattern, with B planes being reflections of the A planes along the same axes as the planes themselves. The distance between oxygen atoms along each bond
12995-411: Was found at extremely high pressures and −143 °C. At even higher pressures, ice is predicted to become a metal ; this has been variously estimated to occur at 1.55 TPa or 5.62 TPa. As well as crystalline forms, solid water can exist in amorphous states as amorphous solid water (ASW) of varying densities. In outer space, hexagonal crystalline ice is present in the ice volcanoes , but
13110-509: Was supplied from Bavarian lakes. From 1930s and up until 1994, the Hungarian Parliament building used ice harvested in the winter from Lake Balaton for air conditioning. Ice houses were used to store ice formed in the winter, to make ice available all year long, and an early type of refrigerator known as an icebox was cooled using a block of ice placed inside it. Many cities had a regular ice delivery service during
13225-569: Was very difficult and seemed to be a random event. In 2001, Salzmann and his coworkers reported a whole new method to prepare ice IV reproducibly ; when high-density amorphous ice (HDA) is heated at a rate of 0.4 K/min and a pressure of 0.81 GPa, ice IV is crystallized at about 165 K. What governs the crystallization products is the heating rate; fast heating (over 10 K/min) results in the formation of single-phase ice XII. The ordered counterpart of ice IV has never been reported yet. 2011 research by Salzmann's group reported more detailed DSC data where
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