Sublimation

The term sublimation is used when a solid heats up, and atoms that make it up for directly from their solid phase to their gas phase, without going through their liquid phase.

Most substances that are solid, at around one atmosphere of pressure, will become liquid, when heated up. Solid Carbon Dioxide, colloquially known as dry ice, is an exception.

At exotic temperatures and pressures other solids sublimate. Water ice sublimates, in a vaccuum.