Diffussion:

Diffusion is the movement of ions or molecules from a region of higher concentration to a region of lower concentration. Movement of molecules in diffusion is spontaneous process and it is caused due to the kinetic
energy of molecules. Diffusion occurs until the equilibrium in the concentration of ions or molecules is attained. Pressure excited by the diffusing ions (water) or molecules is called diffusing pressure or Potential ability of a substance to diffuse from an area of its greater concentration to the area of its lower concentration. The difference in concentration between the two regions before diffusion occurs is known as the diffusion gradient.

Factors affecting diffusion:

There are several factors affecting diffusion. They are as follows.
a. Temperature: The rate of diffusion increase with the increase in the temperature.
b. Size of molecule: The rate of diffusion is inversely proportional to the square root of density of diffusing substance. This is called Graham’s law of diffusion, D =1/√d
c. Diffusion medium: The rate of diffusion will be slower if the medium is highly concentrated.
d. Diffusion pressure gradient: The rate of diffusion is increased with the increase in DPG.

Significance of diffusion:

•  Gaseous exchange during the process of photosynthesis and respiration takes place by the help of diffusion pressure.
•  The process of diffusion is involved in the transpiration of water vapor.
• Aroma of flowers is due to diffusion of volatile aromatic compounds. Diffusion helps in the translocation of food materials.
• Some of the products of digestion in animals are absorbed from ileum by diffusion.