What is dry ice?
Dry ice is basically solidified carbon dioxide, and is called so because the gas on solidifying gives an appearance similar to that of ice. Unlike ordinary ice, it does not melt into a liquid but changes directly into CO2 gas, a phenomenon known as sublimation. It changes into gaseous state at and above -78.5 degree Celsius. As this temperature is much lower than water, it is much colder than water ice. Its density varies from 1.2 - 1.6 g / cm3. It is therefore denser than water.
It is mainly used as a cooling agent because it has temperature lower than that of water ice. It is used for preserving frozen foods, ice cream etc.