甚麼是乾冰??

Dry ice
Dry ice is a genericized trademark for solid (frozen) carbon dioxide. The term was made in 1925 by Prest Air Devices, founded in Long Island City, New York in 1923.[1] The name refers to the fact that under normal atmospheric pressure, solid CO2 sublimates, or changes directly into a gas without passing through a wet liquid phase. As a general rule, dry ice will sublimate at a rate of five to ten pounds every 24 hours in a typical ice chest.

Dry ice is produced by compressing carbon dioxide gas to a liquid form, removing the heat produced by the compression (see Charles's law), and then letting the liquid carbon dioxide expand quickly. This expansion and the high-speed evaporation of carbon dioxide gas cools the remainder of the liquid down to the melting point, where some of the CO2 freezes into 'snow,' which is then compressed into pellets or blocks. The freezing point of CO2 is -109.3 °F or -78.5 °C.

Dry ice has many industrial uses, including


Dry ice used to cool drinks in Central Park.
(New York City, New York, U.S.)Cooling foodstuffs, biological samples, and other perishable items, particularly for shipment.
Producing dry ice fog for special effects. When dry ice is put into contact with water vapour particles, the frozen carbon dioxide sublimates into a mixture of cold carbon dioxide gas and cold humid air. This causes condensation and the formation of fog (see: fog machine). The use of warm water speeds up sublimation and leads to more vigorous production of fog.
Tiny pellets of dry ice (instead of sand) are shot at a surface to be cleaned. Dry ice is not as hard as sand, but it speeds processing by sublimating to a gas and does not produce nearly as much lung-damaging dust.
Increasing precipitation from existing clouds or decreasing cloud thickness by cloud seeding.[2]
Producing carbon dioxide gas as needed in such systems as the fuel tank inerting system in the B-47 Stratojet aircraft.
Brass or other metallic bushings are buried in dry ice to shrink them so they will fit inside a machined hole. When the bushing warms back up, it expands and makes an extremely tight fit.
As a cooling supplement for high power output computer central processing units or other types of hardware. Typically used by hobbyists when performing overclocking.
A rudimentary cloud chamber can be built using dry ice to supercool alcohol vapor.
Dry ice requires special precautions when handling. It is cold enough to cause frostbite injury if handled without gloves. It constantly produces carbon dioxide gas, so it cannot be stored in a light duty sealed container as the pressure buildup will quickly cause the container to explode (see dry ice bomb). The sublimated gas must be ventilated; otherwise, it may fill the enclosed space and create a suffocation hazard. Special care for ventilating vehicles is needed as well because of the small space. People who handle dry ice should also be aware that carbon dioxide is more dense than air and will sink to the floor. Some markets require those purchasing dry ice to be 18 years of age or older.

乾冰，即固體二氧化碳。

乾冰是二氧化碳的凝結固態。乾冰的溫度是攝氏的負78.5度，因此在保持物體維持冷凍或低溫狀態下非常有用 .乾冰能夠急速的冷凍物體和降低溫度並且可以用隔離手套來做配置。 現在乾冰已經被廣泛的使用在許多層面了，乾冰在溶解時是由固態直接昇華為氣態，直接轉化為氣體而省略掉轉為液態的程序，因此其融化並不會產生任何水或液體，也因此我們稱它做「乾冰」。要將二氧化碳變成液態，就必須加大壓強才會出現液態二氧化碳。

應用
造人造雨：利用飛機將乾冰灑在雲上，雲中的小水滴就會被凍結成許多小冰晶，促使更多的水蒸氣凝結在上面，化為雨滴，降落到地面。
製照雲霧：由於乾冰的溫度很低，昇華後低溫的二氧化碳氣體碰到空氣後，可以使空氣中的水蒸氣凝結成小水滴，所以有白煙出現，所以舞臺表演上，常使用乾冰來製造雲霧般的特殊效果。
冷凍劑：由於二氧化碳比空氣重，乾冰昇華後仍可包覆在冷凍的物品上，能夠維持較好的冷凍效果，尤其是在空運需要特別冷凍的物品，往往都使用它。