Name the phase change in each of these events:

(a) A diamond film forms on a surface from gaseous carbon atoms in a vacuum.

(b) Mothballs in a bureau drawer disappear over time

(c) Molten iron from a blast furnace is cast into ingots (“pigs”).

Diamond is a crystalline form of carbon atoms with anisotropic properties.

When a diamond film is formed using the gaseous carbon atoms under a vacuum, the gaseous form gets converted into a solid form.

Mothballs are solid balls made up of chemical pesticides and deodorants that are used for storing clothes and other materials.

Mothballs in a bureau drawer disappear because of the low value of heat of sublimation. The heat of sublimation is so low that it can be achieved even at room temperature for long hours. Thus, for long hours, the mothballs get sublimate slowly and thus disappear.

Ingots are blocks of metal. It is the first semi-finished casting product in the manufacturing process

Molten iron (from blast furnace) is in the liquid phase which during casting converts to the solid phase.