Question

Why solid do not undergo diffusion whereas liquids and gases undergo diffusion readily?

Answer 1

In solids , the particles are tightly packed therefore the kinetic energy is low and hence solids do not undergo diffusion.
whereas liquids and gases the particles are less tightly packed and hence diffusion occurs faster.
Hope this helps you.☺☺☺

Answer 2

Because the particles of solids are tightly packed that's why solids do not undergo diffusion whereas, liquid and gas are undergo diffusion because these particles are not tightly packed, these particles are freely..