Diffusion

The movement of molecules, atoms, ions of gases, liquid or solids from region of higher concentration to region of lower concentration until the molecules get uniformly distributed irrespective of the law of gravitation.

Diffusion Pressure:- It can be defined as the potential ability of a molecule or ions ( solid, liquid or gas ) to diffuse from the area of greater concentration to an area of lesser concentration. The diffusion pressure is directly proportional to the concentration or number of diffusing particles.

Factors affecting diffusion:- i) Rate of diffusion is directly proportional to the temperature.
ii) The rate of diffusion is inversely proportional to sequare root of the density of the diffusing substance.  
iii) The rate of diffusion is directly proportional to the surface area from which diffusion occurs.
iv) Rate of diffusion is directly proportional to the difference of diffusion pressure at the two ends.

Importance:- i) The exchange of gases e.g CO2 intake and O2 output in photosynthesis and CO2 output or O2 intake in respiration takes place by the principle of independent diffusion.

ii) The process of diffusion involved in the transpiration of water vapours.

iii) The ions are absorbed by the simple diffusion during passive salt intake.

iv) Diffusion is an effective means of transport of substances over a very short distances.