<P> Sublimation requires additional energy and is an endothermic change . The enthalpy of sublimation (also called heat of sublimation) can be calculated by adding the enthalpy of fusion and the enthalpy of vaporization . </P> <P> Solid carbon dioxide (dry ice) sublimes everywhere along the line below the triple point (e.g., at the temperature of − 78.5 ° C (194.65 K, − 104.2 ° F) at atmospheric pressure, whereas its melting into liquid CO can occur only along the line at pressures and temperatures above the triple point (i.e., 5.2 atm, − 56.4 ° C). </P> <P> Snow and ice sublime, although more slowly, at temperatures below the freezing / melting point temperature line at 0 ° C for most pressures; see line below triple point . In freeze - drying, the material to be dehydrated is frozen and its water is allowed to sublime under reduced pressure or vacuum . The loss of snow from a snowfield during a cold spell is often caused by sunshine acting directly on the upper layers of the snow . Ablation is a process that includes sublimation and erosive wear of glacier ice . </P> <P> Naphthalene, an organic compound commonly found in pesticide such as mothball also sublimes . It sublimes easily because it is made of non-polar molecules that are held together only by van der Waals intermolecular forces . Naphthalene is a solid that sublimes at standard atmospheric temperature with the sublimation point at around 80 _̊ C or 176 _̊ F. At low temperature, its vapour pressure is high enough, 1 mmHg at 53 _̊ C, to make the solid form of naphthalene evaporate into gas . On the cool surface, the sublimated vapour will be solidified to form a needle - like crystal . </P>

Substance that changes to a gas easily at room temperature