Factors Affecting Rate of Diffusion (p. 149)

solvent density

as the density of a solvent increases, the rate of diffusion decreases

extent of the concentration gradient

greater the difference in concentration, the more rapid the diffusion. closer the distribution of the material gets to the equilibrium, slower the rate of diffusion becomes

mass of the molecules diffusing

heavier molecules move more slowly and therefore diffuse more slowly (reverse is true for lighter molecules)

temperature

higher temperatures increase the energy and therefore the movement of the molecules, increasing the rate of diffusion. lower temperatures decrease the energy of the molecules, thus decreasing the rate of diffusion

surface area and thickness of the plasma membrane

increased surface area increases the rate of diffusion, whereas a thicker membrane reduces it

solubility

nonpolar or lipid-soluble materials pass through plasma membranes more easily than polar materials, allowing a faster rate of diffusion

distance travelled

the greater the distance that a substance must travel, the slower the rate of diffusion