Dry Ice

Dry Ice
Dry ice, sometimes referred to as “Cardice” or as “card ice” is the solid form of carbon dioxide. Dry ice is used as a cooling agent. Dry ice is the solid form of carbon dioxide (chemical formula: CO2), comprising two oxygen atoms bonded to a single carbon atom. It is colourless, odourless, non-flammable, and slightly acidic.
Sublimation and Deposition
Many materials have clear  Triple changing points Gas, Liquid, and Solid by the temperature and pressure. Is usually most substance molecules by heat and pressure vibration and begin, but it is not be a molecular position change. And next  liquid state begins to gravitas (melting point), while molecules together sticks and begins to move freely.  And further increase highpressure or temperature, Molecules are completely apart and popping in the air, Most people  anyone know it. However,because of   the nature of the substance  under  the temperature where we lived at room suddenly become  gas individual phenomenon is seen, such as carbon dioxide. Solid state is Christmas cake that come with dry ice.
    CO2 changes from a solid to a gas with no intervening liquid form, through a process called sublimation. The opposite process is called deposition, where CO2 changes from the gas to solid phase (dry ice). Actuary at temperatures above −56.4 °C (−69.5 °F) and pressures below 5.2 bar, we can watch this phenomenon, and under the conditions more high temperature and pressure 3 steps apears including liquid. However, the liquid is seen in our everyday lives.
 It is generally accepted that dry ice was first observed in 1834 by French chemist Charles Thilorier, In 1925, this solid form of CO2 was trademarked by the DryIce Corporation of America as “Dry ice”, thus leading to its common name. Carbon dioxide-rich gas is pressurized and refrigerated and commercialization.
Molecular Join
 Often this relation of the molecule is very weak for mostly changable alternative easily to liquid or gas in the low-temperature of 100 degrees or less, but  the ion binding has a strong relation is haunting and needs  high temperature to separate itselves.  For example, NaCl  is seen liquefied phenomenon at 800 Degrees.

昇華と蒸着
 
この両方を昇華とも言う。通常ほとんどの物質は分子が熱や圧力によって振動し始めるが分子位置が変わることはない。しかし液体の状態になり融けだすと(これを融点という)分子同士が密着しながらも自由に動き回りだす。そしてさらにハイプレッシャーまたは温度を上げると分子が完全にバラバラになり空気中に躍り出るかたちになるのは、ほとんどの人が誰でも知っている。しかし、物質の特性によって二酸化炭素などは私たちが住む常温下でいきなり個体が気体になる現象がみられる。この固体状態がクリスマスケーキに付いてくるドライアイスである。実際には5.2気圧を超えると液体の状態が現れる。
分子結合
このように分子同士の結びつきは非常に弱いために大抵100度以下の低温でも液体や気体に代わることが多いが、イオン結合の場合には結びつきが高温でなければ簡単には離れない。例えばNaclは高温になると液化現象がみられる。

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