Answer :
(Part one) 1 . Diffusion : when concentration of a substance in one side of membrane is more than other side the substance diffuse over membrane to side with lower concentration this mechanism no need to energy .
Osmosis is a special case of diffusion. Water, like other substances, moves from an area of higher concentration to one of lower concentration. ... In this example, the solute cannot diffuse through the membrane, but the water can. Water has a concentration gradient in this system.
