Question

Naphthalene balls dissappear with time without leaving any solid.why?

Answer 1

because they directly changes from solid to gaseous form
this process is called as sublimation

Answer 2

napthalene balls goes under the process of sublimation which state that the solid will convert into gas amd vice - versa without changing its state into liquid form(state) though they(napthalene balls) disappear with time with out leaving anysolid beacause the balls get converted into gas state and gaseous state doesn't have any solid formations.
hope it helps,Thankyou