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Physical properties
Natural formation
Ablation
Role in human activities
Impacts of climate change
Non-water
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Ice
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From Wikipedia, the free encyclopedia
This article is about water ice. For the broader concept of "ices" as used in the
planetary sciences, see Volatile (astrogeology). For other uses, see Ice
(disambiguation).
Ice
An ice block, photographed at the Duluth Canal Parkin Minnesota
Physical properties
Density (ρ) 0.9167[1]–0.9168[2] g/cm3
Refractive index(n) 1.309
Chemical properties
Chemical formula H 2O
Mechanical properties
Young's modulus(E) 3400 to 37,500 kg-force/cm3[2]
Tensile strength(σt) 5 to 18 kg-force/cm2[2]
Compressive strength (σc) 24 to 60 kg-force/cm2[2]
Poisson's ratio (ν) 0.36±0.13[2]
Thermal properties
Thermal conductivity (k) 0.0053(1 + 0.0015 θ) cal/(cm s
K), θ = temperature in °C[2]
Linear thermal expansion 5.5×10−5[2]
coefficient (α)
Specific heat capacity (c) 0.5057 − 0.001863 θ cal/(g K), θ=
absolute value of temperature in °C[2]
Electrical properties
Dielectric constant (εr) ~95[3]
The properties of ice vary substantially with temperature, purity and
other factors.
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 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 structuredenoted as ice
Ih (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 Ih occurs when liquid water 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 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 glaciersand 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 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 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.
Physical properties
Further information: Water (properties) § Density of water and ice
The three-dimensional crystal structure of
H2O ice Ih (c) is composed of bases of H2O ice molecules (b) located on lattice points
within the two-dimensional hexagonal space lattice (a).[4][5]
Ice possesses a regular crystalline structure based on the molecule of water, which
consists of 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.[6]
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 is equivalent to
a volumetric expansion of 9%. The density of ice is 0.9167[1]–0.9168[2] g/cm3 at 0 °C
and standard atmospheric pressure (101,325 Pa), whereas water has a density of
0.9998[1]–0.999863[2] g/cm3 at the same temperature and pressure. Liquid water is
densest, essentially 1.00 g/cm3, at 4 °C and begins to lose its density as the water
molecules begin to form the hexagonal crystals 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. The density of ice
increases slightly with decreasing temperature and has a value of 0.9340 g/cm3 at
−180 °C (93 K).[7]
When water freezes, it increases in volume (about 9% for fresh water).[8] The effect of
expansion during freezing can be dramatic, and ice expansion 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.[9]
This iceberg can stay afloat in spite of its
size because it is less dense than water
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 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.[10] 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 the bald notothen, fed upon in
turn by larger animals such as emperor penguins and minke whales.[11]
