j However, as the ice melts to give fresh (not salty) water, which is less dense than the salty sea water, a very small rise in sea level does occur. Īs sea ice floats on water, displacing its own weight of water, it is often saidt that when such ice melts (caused by global warming), the water level should not rise. This phenomenon appears to be a general property of any material that expands on freezing. Ice spikes that occasionally grow out of (pure water) ice cubes ĭue to the expansion on freezing, an interesting phenomenon is On freezing. In contrast, freezing liquid water under high pressure to the more dense ice VI causes ilittle structural damage. Pressure, causes extensive tissue damage in biological organisms On melting to form liquid water. The expansion in volume when going from liquid to solid, under ambient In contrast, it should be noted that the high-pressure ices ( ice III, ice V, ice VI, and ice VII) all expand In the liquid phase requires more space and therefore melting This is different from most solids, where the extra movement available Silica (responsible for the Earth's crust floating on the Other tetrahedrally arranged solids such as On melting, some of these ice (Ih) bonds break, others bend, and the structure undergoes a partialĬollapse. All the water moleculesĪre involved in four straight, tetrahedrally-oriented hydrogenīonds for comparison, solid hydrogen sulfide has a face-centered,Ĭubic closed packed structure with each molecule having twelve The expansion of ice, compared with liquid water, is why erosion is caused by the cracking of rocks when contained moisture freezes The molar volumes of ice and water along the melting point curve are shown right. On freezing is even more significant (for example, 16.8% at -20 ☌ ). Point is lowered by increased pressure, the increase in volume When water freezes at 0 ☌, its volume increases by about 9% under atmospheric pressure therefore, ice floats on water (see above).

Other materials that expand on freezing are silicon, gallium, germanium, antimony, and bismuth. Solid but require more space to move around within the liquid. This is because the molecules are in fixed positions within the It is usual for liquids (even hydrogen-bonded liquids like ethanol and hydrogen peroxide) to contract on freezing and expand on melting (e.g., liquid oxygen shrinks 19% on freezing, and molten lead shrinks 6.4% on freezing). Ĭhanges in the molar volume of water and iceĭown the melting point curve, from Similar anomalous behavior is expected in ices Ic, III, V, IX, XII, XIII, XIV, and XVI.Īccurate and precise lattice parameters for H 2O ice Ih and D 2O ice Ih have been determined between 1.6 K and 270 K. A lower density is usually expected for such isotopic changes due to the intramolecular vibrational O–H stretching modes of the hydrogen bonds. Ī further ice density anomaly concerns the high molar volume of heavy water hexagonal ice compared with that of light water (see above right). Over the range, 80-160 K, the density of high-density ( HDA) amorphous ice decreases on isobaric heating above ≈ 0.35 GPa but increases at lower pressures. Interestingly, the density maximum for hexagonal ice is about 72 K at ambient pressure, and this is the maximum temperature for its catalyzed phase transition to ice XI. This phenomenon is similar but unrelated to the maximum density anomaly that occurs in liquid water. To alteration in the net bending motion of three tetrahedral hydrogen-bonded molecules with temperature,Īs higher frequency modes are reduced. This low-temperature expansion appears to be due Thermal expansivity at about 33 K (expansionĬoefficient (α) ≈ -0.000003 K −1). However, allĮxpand slightly with cooling at all temperatures below about 70 K with a minimum Hexagonal, cubic, ice XVI, and low-density amorphous ice all become denser at low temperatures. Most solids expand and become less dense when heated. The change in volume as liquid changes to gas is very large The refractive index of water has a maximum The NMR shift increases to a maximum at low (supercooled) temperatures The NMR spin-lattice relaxation time is very 'Fast sound' is found at high frequencies and shows a discontinuity at higher pressure The speed of sound increases with temperature There is a maximum in the compressibility-temperature relationship The number of nearest neighbors increases Thermal expansivity increases with increased pressure Water's thermal expansivity reduces increasingly Pressure reduces the temperature of maximum The surface of water is denser than the bulk That increases on warming (up to 3.984 ☌) '.water has the remarkable property of being more compressible in winter than in summer.' Of the Density Anomalies of Water (D1-D22)

Density of water in lbin3