What is Dry Ice?
When you freeze carbon dioxide, the end product will be dry ice. Carbon dioxide is what animals and humans exhale in which plants utilize for the production of their food or the process called photosynthesis. Dry ice has a very low temperature and is typically used as coolant. The temperature of this frozen carbon dioxide is at -109.73 degrees Fahrenheit or -78.5 degrees Celsius. Relatively, dry ice is not difficult to produce.
Dry ice is often used by scientists in small amount. To be able to produce a small amount of dry ice, the valve of the liquid carbon dioxide tank is opened. In the nozzle where the carbon dioxide is discharged, a cloth bag is put to act as a catcher. When some parts of the gas escaping from the cloth condenses, a blend of dry ice and gaseous carbon dioxide is produced. Scientists use this method when they just want a small amount of dry ice for laboratory use. This method is considered to be the easiest way or the most unsophisticated way of creating dry ice.
However, when there is a need to produce large amounts of frozen carbon dioxide or dry ice, the evaporative cooling method is utilized. The first step in evaporative cooling is to produce liquefied carbon dioxide. This is done when carbon dioxide gas is compressed. Compression process increases the temperature of a substance. Therefore in order to liquefy such substance, the gas must be cooled while under the process of compression. Liquefaction starts to happen when the gas contained in a vessel is approximately at room temperature. Moreover, the pressure must be at about 6,000 kilopascals or 870 ppsi.
The next step is the actual process of creating dry ice. It was known that matter contains both fast and slow moving molecules. These molecules have an average velocity and that is what scientists call temperature. The idea is to let more fast moving molecules to escape through evaporation. This will leave slow moving molecules and therefore it means that the temperature will also start to decrease. As more active molecules escape, more heat evaporates. This will leave the temperature to reach below freezing point. After a phase transition occurs frozen carbon dioxide is the end result. This is what people call dry ice.
To keep dry ice from melting, it must be contained in an insulated container. Actually, dry ice does not melt. Instead, it instantly starts to emit carbon dioxide gas. Dry ice misses out passing through the liquid phase and just instantly turns into gas. This is due to the reason that the disparity of the temperature between the environment and the dry ice is adequately great. This is also the reason why dry ice gives off smoke or what most people call fog. This characteristic of dry ice makes it perfect in producing artificial fog. Typically it is useful in stage presentation or performances. Other stage shows combine fog produced by dry ice with laser lights to give attractive effects for the viewers.