Naphthalene balls disappear with time without leaving any solid. Which process is invovled?

Anything that moves in a net direction from a location of higher concentration to a region of lower concentration is said to be diffusing. A gradient in concentration drives diffusion. The direct transfer of a material from the solid to the gas state is known as sublimation.

Naphthalene balls vanish with time, leaving nothing substantial behind. Naphthalene easily undergoes sublimation, or the transition from a solid to a gas without the help of a liquid state. As a result, naphthalene balls continue to produce naphthalene vapours that gradually dissipate into the air without leaving any solid behind.

Hence, the correct answer is B.