What is diffusion and what effects the rate at which it occurs?

Diffusion is the movement of particles from an area of high concentration to an area of low concentration (with the gradient). Once the concentration in each area is equal, the overall diffusion rate is 0. What does this mean? Imagine you spray some air freshener in one corner of your room, how come within a few seconds you can smell it at the other side of the room? This is diffusion in action! When you spray the air freshener, the concentration of the particles in that corner of the room is incredibly high whereas the concentration of particles in the rest of the air is low. The difference in these concentrations is called a gradient. The particles don’t like to all be concentrated in one area so they begin to spread throughout the air towards the areas of low concentration. Eventually, the concentration within the air will be equal. This same thing happens within the body: such as the movement of oxygen across the membrane and into cells. The rate at which this diffusion occurs depends on 3 factors: surface area (the greater the surface area, the faster diffusion will occur), the gradient (the higher the difference in concentrations, the faster diffusion will occur) and the thickness of the exchange surface (the thinner it is, the quicker diffusion will occur). So the ideal situation for diffusion is a large surface area, a high gradient and a thin surface.