Ice

Ice is water frozen into the solid state. It can appear transparent or opaque bluish-white color, depending on the presence of impurities or air inclusions. The addition of other materials such as soil may further alter the appearance.
Ice appears in nature in forms of snowflakes, hail, icicles, ice spikes and candles, glaciers, pack ice, frost, and entire polar ice caps. It is an important component of the global climate, and plays an important role in the water cycle. Furthermore, ice has numerous cultural applications, from ice cooling of drinks to winter sports and the art of ice sculpting.
The molecules in solid ice may be arranged in different ways, called phases, depending on the temperature and pressure. Usually ice is the phase known as ice Ih, which is the most abundant of the varying solid phases on the Earth's surface. The most common phase transition to ice Ih occurs when liquid water is cooled below  at standard atmospheric pressure. It can also deposit from vapour with no intervening liquid phase, such as in the formation of frost.
==Uses==
===Sports===
Ice also plays a central role in winter recreation and in many sports such as ice skating, tour skating, ice hockey, ice fishing, ice climbing, curling, broomball and sled racing on bobsled, luge and skeleton. Many of the different sports played on ice get international attention every four years during the Winter Olympic Games.
A sort of sailboat on blades gives rise to ice yachting. The human quest for excitement has even led to ice racing, where drivers must speed on lake ice, while also controlling the skid of their vehicle (similar in some ways to dirt track racing). The sport has even been modified for ice rinks.
===Other uses===
*Ice cubes or crushed ice can be used to cool drinks. As the ice melts, it absorbs heat and keeps the drink near .
*Ice can be used to reduce swelling (by decreasing blood flow) and pain by pressing it against an area of the body.
*Engineers used formidable strength of pack ice when they constructed Antarctica's first floating ice pier in 1973. Such ice piers are used during cargo operations to load and offload ships. Fleet operations personnel make the floating pier during the winter. They build upon naturally-occurring frozen seawater in McMurdo Sound until the dock reaches a depth of about. Ice piers have a lifespan of three to five years.
*Structures and ice sculptures are built out of large chunks of ice. The structures are mostly ornamental (as in the case with ice castles), and not practical for long-term habitation. Ice hotels exist on a seasonal basis in a few cold areas. Igloos are another example of a temporary structure, made primarily from snow.
*During World War II, Project Habbakuk was a British programme which investigated the use of pykrete (wood fibers mixed with ice) as a possible material for warships, especially aircraft carriers, due to the ease with which a large deck could be constructed, but the idea was given up when there were not enough funds for construction of a prototype.
*Ice can be used to start a fire by carving it into a lens which will focus sunlight onto kindling. A fire will eventually start.
*Ice has even been used as the material for a variety of musical instruments, for example by percussionist Terje Isungset.
* Ice was once used to cool refrigerators in the 19th century, which is reflected in the name "iceboxes."
* Ice can be used as part of an air conditioning system.