Question

Phenomenon in which solid directly changes into vapor is called

Answer 1

Hint: We generally see that a gas is first transformed into liquid then into solid or vice versa. Direct sublimation transition of the phase or a variation in a state of matter as melting, freezing or evaporation. Sublimation is given as the change in the state of matter from solid to gas, directly.

Complete answer:
Sublimation is also a kind of transition of the phase or a variation in a state of matter as melting, freezing or evaporation. Sublimation is given as the change in the state of matter from solid to gas, directly. That means, the intermediate phase called liquid state is not present Phenomenon in which solid directly changes into vapour is called sublimation.
The process of sublimation is a physical change of state. This cannot be helpful in describing the change of state of matter from the solid to liquid in a chemical reaction. There are a lot of examples for this process. Dry ice is a common example for this. Sublimation is due to the absorption of heat which will give needed energy for certain molecules in order to overcome the forces of attraction due to their neighbor molecules and change into the vapour state directly. As we said, the process needs extra Energy; this will be an endothermic process. The enthalpy of sublimation or the heat of sublimation is determined by summation of the enthalpy of fusion and the enthalpy of vaporization.
Therefore, Phenomenon in which solid directly changes into vapor is called Sublimation.

Note:
Remember that there is in this process the solid directly into gas without entering the liquid phase. For Example- when camphor or naphthalene balls are heated they undergo sublimation and directly change to gas phase without passing through liquid phase.