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Hydrological cycle
Hydrological cycle
A scientific term for the water cycle.
All ice crystals are single crystals, often with branching patterns. A single snowflake
is a single ice crystal. Most “snowflakes” are in fact groups, or
aggregates, of snowflakes.
When a body of liquid water
such as a river, lake, or sea turns to ice, the surface
freezes first. Even raindrop surfaces can freeze, in which case the frozen
drops form hail. Partly melted ice crystals are called sleet. (See also:
Precipitation.) The largest
amounts of solid ice are found in the world’s ice
sheets, most notably in Antarctica, Greenland,
and the Arctic Sea.
Ice conducts electricity
much more easily than most solids. Only metals conduct
electricity better.
The ice that grows from liquid
water is a crystalline material that is made of interlocking crystals. Because the crystals do not have well-defined faces, as they do in snowflakes, this form of ice appears to be a transparent, featureless
solid rather than having the shiny surface of a crystal. Scientists call it an amorphous solid. The same property is true of other transparent materials such as glass.
Ice will only melt when sufficient heat has been added.
The heat needed for melting is called the latent heat of fusion. The temperature of the ice does not rise while heat is being absorbed in the melting process.
The amount of heat needed to melt a gram of ice is 337 joules (0.337 kilojoules), or 80 calories. This is a much higher amount of heat than is needed to melt most
 Ice—Ice is one state of water. Ice will change state to liquid water as it melts. It will also directly change to water vapor, a process called sublimation.
I
Ice
The solid form of water. It can
be produced by the freezing of liquid water or directly from vapor (a process called sublimation). Frozen water vapor is called frost when it is on the ground and ice crystals or snowflakes when formed in a cloud.
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