Summary of Diffusion: (what you need to remember)
Diffusion is the random, thermal motion of particles.
Net diffusion is the movement of particles from an area of higher concentration to an area of lower concentration.
Net diffusion can never move particles against a concentration gradient.
Therefore, substances will diffuse only from an area of higher concentration to an area of lower concentration.
Diffusion is considered a passive transport process as it does not utilize any cellular energy.
Equilibrium is defined as the state in which there is no net change in a system (solute concentration remains constant).
IF diffusion is the only force acting on a system, equilibrium will occur when the concentrations of solutes are equal. Please note that if there are other forces acting on the system, it is possible for equilibrium to occur when the concentrations of solutes are NOT equal.