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Should be noted about Salt water

Saline water is water with salt in it. It often means the water from the seas (sea water) and oceans.

Salt water is more dense than fresh water.

Salt water needs a lower temperature to freeze than pure water. The resulting ice contains much less salt than the salt water it came from. This salty ice is not as strong as frozen pure water. Similarly spreading salt on ice melts it, if it's not too cold: the salt progressively eats into the ice, forming brine which is not cold enough to be frozen at the same temperature.

Geographical locations of ice

Because ice floats, even large bodies of water that freeze, like some oceans, only form ice on the surface. Most lakes never freeze to the bottom. Even the coldest oceans, like the Arctic Ocean, only freeze on the top, leaving liquid ocean circulating below. Because of this the Earth's oceans are able to redistribute heat and the climate of the earth has less extremes of heat and cold than it would otherwise. If ice were to sink instead of float, the oceans would fill up with ice from the bottom, would remain solid and only some of the top would melt. A solid ocean would not circulate heat. But because ice floats on the surface the water beneath can continue to circulate and the ice on the surface stays exposed and readily melts when the temperature rises. Antarctica has the majority of the world's ice.

Dry ice

Dry ice, or solid carbon dioxide, is the solid state of CO2 gas below -78.5 C. Dry ice does not occur naturally on earth but is man made. It is colorless. The gas is so cold that when it mixes with air it cools the water vapour in the air to fog, which looks like a thick white smoke. It is often used in the theatre to make fake fog or smoke.

Hail

A piece of hail (called a hailstone) is a lump of ice that falls out of a storm cloud.

A hailstone begins as a small water drop or a round snow pellet in a cloud. The drop grows by collecting many cloud drops. The little drop is blown by a strong wind inside the cloud to where it meets with some extremely cold water drops. These supercooled drops are still liquid water even though the temperature is below freezing. When the little drop mixes with these extremely cold drops, they join, and the little drop has now become a hailstone.

The little hailstone is thrown up inside the cloud, still collecting other cold drops. The hailstone gets bigger and bigger until it goes to the top of the cloud. Then, because there is no more wind, it falls back down through the cloud. While it is falling it gets even bigger as it bangs into more supercooled drops. If it goes down very fast it can hit the earth at up to 90 mph (144 kph), bouncing like popcorn. If the hailstone hits dirt, it can actually bury itself.

Hailstones are made of many rings of clear, cloudy ice. The rings show different amounts of freezing on the hailstone. The cloudy ice is because it freezes so quickly, trapping many small air bubbles. The clear rings are made by slow freezing of the water, which lets bubbles escape.



Sleet

Sleetis a term for ice pellets that is used in the United States and Canada. Ice pellets are usually smaller than hailstones. Sometimes, ice pellets bounce when they hit the ground.

Snow

Snow is a form of ice. Snow forms when water in the atmosphere becomes frozen. Snow comes in all different shapes and sizes.

At the freezing point of water (0 Celsius, 32 Fahrenheit), snow melts and becomes liquid water. Sometimes, the snow will melt very fast and become water vapor. This is called sublimation. The opposite, where water vapor becomes snow, is called deposition.

Snow can also be dangerous, as it can lower visibility .When it snows, the snow will melt a little during the daytime and freeze again at night. This makes ice which can provide avalanche. When salt is mixed with snow , the snow will melt more easily. This is because salt water has a lower melting point than fresh water (water without salt).

Blizzard

A blizzard is a dangerous type of a snowstorm. It brings low temperatures, strong winds, and a lot of blowing snow. Blizzards start when a high pressure system touches as low pressure system., and can produce thunder snow, which is snow with lightning and thunder. A blizzard is like a thunderstorm except a blizzard has mostly snow instead of rain, although in some cases snow and rain can be present. Blizzard can occur in any place where snow falls. In North America, blizzards happen often in the northern-east states, and in the provinces of Canada. In this region, blizzards can happen more than twice each winter. They also occur often in the mountain ranges of western North America.

Whiteout

A very dangerous type of blizzard is a whiteout. In a whiteout, downdrafts and snowfall are so thick that people cannot tell the ground and sky apart. People caught in a whiteout lose their sense of direction very fast.

Downdraft

An updraft or downdraft is the vertical movement of air as weather causes two forces to move.


Date: 2016-01-03; view: 249


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