Introduction

 Movement of ions , gases, solute from their higher concentration to lower concentration is called diffusion. Eg:- If a drop of ink is dropped into the glass containing water ,  very soon its molecules become distributed throughout the glass.

Experiment of diffusion

                         When a crystal of CuSO₄ is placed in a beaker containing water, a dense blue color is sen around the crystal. It decrease with increase in distance from the Crystal representing the diffusion of the CuSO₄  molecules moves towards water and water moves toward the CuSO₄. Finally , the molecules of both water and CuSO₄  are distributed equally throughout the solution.

Diffusion pressure

                      The pressure exerted by the diffusing ions or molecules  to diffuse from the area of its higher concentration to lower concentration is called diffusion pressure.

Experiment of diffusion pressure:-

                   Fill a rubber ballon with any gas. The gas molecules are confined to space within the ballon and their molecules exerts a pressure on the wall of the ballon. Now, prick the ballon. Gases released immediately and collapsed the ballon. The pressure under which gas will release from the ballon represents the diffusion pressure.