Mothballs in a clothes closet gradually disappear over time, because their components sublime.
Mothballs are small balls of chemical pesticide and deodorant, sometimes used in closets where clothes are susceptible to damage from mold or moths. Mothballs are usually made of naphthalene, 1,4-dichlorobenzene or camphor. What all the compounds have in common is that they sublime at room temperature. Sublimation is a physical change in which matter changes from the solid to the gas state. Once the components are in the gaseous state, the diffuse, and that's why there are no visible remainings over time.
Mothballs in a clothes closet gradually disappear over time, because their components sublime.
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