Properties of Ice I
Why Worry about Ice?
Engineers and Ice
Types of Ice Commonly
Found in Nature
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Lake and river ice (freshwater ice)
Sea ice
Glacial ice
Atmospheric ice
Sea spray ice
Snow??
Molecular Structure
• Water molecules
• 1 Oxygen + 2
Hydrogen atoms
• covalent chemical
bonds between
• dipolar moment of
105
• electrical polarity
Hydrogen Bonds
• Electrical polarity
causes attraction
between molecules
• Weak, but significant
“Hydrogen bonds” can
form between
molecules
• Polarity and hydrogen
bonds account for
unique properties
Hydrogen Bond Effects
• Hydrogen bonds cause water to have:
– High heat capacity: can absorb a lot of heat
energy with little increase in temperature
• energy required to break hydrogen bonds
• highest heat capacity of all solids and liquids, except
liquid ammonia
– High latent heat of fusion (energy loss
necessary for freezing): highest except
ammonia
Hydrogen Bond Effects
• Hydrogen bonds cause water to have:
– High latent heat of evaporation (energy
necessary to evaporate): highest of all
substances
– High surface tension: highest of all liquids;
important in formation of droplets and capillary
waves
Phase Changes
Water and Ice Structure
Water has a partially ordered
structure where hydrogen
bonds are constantly being
formed and broken up
Ice has a rigid lattice
structure - each molecule
is bonded to 4 other
molecules
Hexagonal Structure
Ice Density
• Ordered crystalline
structure of Hydrogenbonded ice fills more
volume than randomly
oriented water molecules at their closest
spacing (at 4° C)
Water
Ice
Water Density
Water-Ice Density Change
Water Density
• Density of liquid water:
  1000  1.9549  10
– T = degrees Celsius
–  = kg/m3
  62 .4  4.5441  10
– T = degrees Fahrenheit
–  = lbs/ft3
2
4
T 4
1.68
T  39 .2
1.68
Density of Freshwater Ice
• Density of freshwater ice at 0 °C is 916.8 kg/m3
(57.2 lb/ft3)
• Ice contracts with cooling, like most substances; at
-30 °C the density is 920.6 kg/m3 (57.4 lb/ft3)
• Bulk ice density is most affected by air bubbles
and pockets of unfrozen water
• for most engineering, use  = 915-917 kg/m3
(57.1-57.2 lb/ft3) for freshwater ice
Conclusion
Ice Floats!
Freshwater Ice Growth
• Static Ice Formation (Thermal Ice Growth)
– Freezing directly to the bottom of the ice sheet
• Quiescent (no wind or turbulence) ice growth
• Heat loss from the ice/water interface to the atmosphere
• Frazil Ice
– Turbulent water associated with streams or rivers
• Slight supercooling (<0.1° C) generally associated with open
water forms disk shaped crystals
• Form from seed crystals such as snow or ice crystals
• Snow Ice
– Freezing of water-saturated snow
Lake Freezing
• Lakes freeze primarily by static (thermal) ice
growth
– Freshwater lakes must completely “turn over,” i.e.,
reach 4°C over the entire volume, before further
cooling can cause freezing to occur.
• Surface water at 4°C sinks, being replaced by warmer water
from below
• Once all the water is < 4°C, colder water stays at the surface
and warmer water stays below – ice can form when most of the
water column is above the freezing point
• Turbulent currents can overcome stratification
Lake Freezing
• Once an ice cover
forms on a lake,
further freezing is
retarded by
insulation from ice
and snow cover
River Freezing
Rivers freeze with a
combination of thermal
and frazil ice growth
Frazil nearly always
precedes thermal or
static ice growth
Frazil Ice
Frazil Crystals
Frazil Flocks or Pans
River Ice Evolution
Lake and River Ice Crystal Structure
Frazil Ice
Snow Ice
Vert. C-axis
Vert. C-axis
Horz. C-axis
Lake Ice
River Ice
Glacier Ice
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Compaction of snow into ice
Vertical sequence of snow, firn, ice
Usually more dense than lake or sea ice
Flows outward under its own weight and
downslope
• Calves at seaward terminus - icebergs
Glacial Ice Structure
Antarctic Ice Core – 194 m depth
Iceberg!!
• Icebergs are calved
from ice sheets and
glaciers
• A reminder: Since the
densities of ice and
water are close, 85 90% of an ice mass is
beneath the surface