Diffusion is the process by which particles (such as molecules or atoms) move from an area of higher concentration to an area of lower concentration, resulting in the even distribution of the particles over time. This movement occurs naturally due to the random thermal motion of molecules, and it does not require external energy. Diffusion continues until there is equilibrium, where the concentration of particles is uniform throughout the space, although the molecules continue to move randomly.
Key Points About Diffusion
- It is a mass transfer phenomenon driving chemical species to distribute more uniformly in space over time.
- The driving force is the random thermal motion of molecules, which causes them to spread out from regions of high concentration to low concentration.
- Diffusion occurs in gases and liquids where particles can move freely, but it is slower or limited in solids.
- It plays a critical role in biological systems, such as the movement of oxygen into cells or the spread of smells in the air.
- The process is described as movement "down a concentration gradient."
- At equilibrium, molecules still move randomly, but there is no net movement in any particular direction.
This concept is fundamental in physics, chemistry, biology, and many other fields where the distribution and movement of particles are relevant.