If the initial pressure of the ice at 0°F is 0.0505 psia, heat transfer to the ice first results in anincrease in temperature to 20°F. At this point, however, the ice passes directly from the solidphase to the vapor phase in the process known as sublimation. Sublimation is a special termused for cases in which the transition between the solid phase and the vapor phase occursdirectly, without passing through the liquid phase. Further heat transfer would result insuperheating the vapor.