Question

Some solids diffuse in liquids but not in gases some solids diffuse in gases but not in liquids why

Answer 1

because liquid are thick in nature 

Answer 2

atoms or molecules that comprise a solid require “assisted mobility” in order to be carried into a liquid medium or a gaseous medium. They don’t spontaneously jump off a solid surface and start swimming in the fluid. The atoms or molecules that comprise the liquid (or gas) would have to penetrate into the solid surface, then interact with individual atoms/molecules of the solid, form some sort of an “adduct” (this could be solvation or simply an electrostatic adduct formation) and then “guide” the solid atoms/molecules into the liquid (or gas) phase.

If you look at solvation process in this manner, you can see that the nature and bonding capability of atoms/molecules in the fluid phase can influence whether a solid can disperse (not diffuse) into one type of fluid phase (e.g. liquid phase) but not the other (e.g. gas phas