Question

Do all substances change from solid to liquid state and from liquid to gaseous state upon heating?

Answer 1

Hint: Think of the process of sublimation and try to remember if this carries out this same transition. If not, then point out which transition it carries out so as to solidify your answer.

Complete step-by-step answer:
Let us look into the process of sublimation, the only phase-change phenomenon that involves the direct transition of a substance in solid state into gaseous state upon heating.
Under some circumstances, the solid phase can transition directly to the gas phase without going through an intermediary liquid phase, and a gas can directly become a solid. The solid-to-gas change is called sublimation, while the reverse process is called deposition. Sublimation is isothermal, like the other phase changes. There is a measurable energy change during sublimation which is referred to as the enthalpy of sublimation and is represented by \[\Delta {{H}_{sub}}\]. The relationship between the \[\Delta {{H}_{sub}}\] and the other enthalpy changes is as follows:
\[\Delta {{H}_{sub}}~=\text{ }\Delta {{H}_{fus}}~+~\Delta {{H}_{vap}}\]
As such, \[\Delta {{H}_{sub}}\] is not always tabulated because it can be simply calculated from \[\Delta {{H}_{fus}}\] and \[\Delta {{H}_{vap}}\].
There are several common examples of sublimation. A well-known product—dry ice—is actually solid \[C{{O}_{2}}\]. Dry ice is dry because it sublimes, with the solid bypassing the liquid phase and going straight to the gas phase. The sublimation occurs at a temperature of −77°C, so it must be handled with caution.
Therefore, we can conclude that the statement that an intermediate phase of transition is not required for a phase change between solid and gas phases and vice versa.

Note: If you have ever noticed that ice cubes in a freezer tend to get smaller over time, it is because the solid water is very slowly subliming. “Freezer burn” isn’t actually a burn; it occurs when certain foods, such as meats, slowly lose solid water content because of sublimation.