sublimation
The process in which a solid changes directly to a gas is called sublimation . It occurs when the particles of a solid absorb enough energy to completely overcome the force of attraction between them. Dry ice solid carbon dioxide, CO 2 is an example of a solid that undergoes sublimation. Figure below shows a chunk of dry ice changing directly to carbon dioxide gas. Sometimes snow undergoes sublimation as well. This is most likely to occur on sunny winter days when the air is very dry. What gas does snow become?.