What does diffusion refer to in a chemical context?

Diffusion in a chemical context refers to the spontaneous spreading out of substances due to the movement of particles. This phenomenon occurs as particles in a substance are in constant motion, and when there is a concentration gradient—meaning an area of high concentration of particles adjacent to an area of low concentration—particles will naturally move from the area of higher concentration to the area of lower concentration. This process continues until the concentration of particles is uniform throughout the space.

Diffusion can be observed in various situations, such as when a drop of food coloring spreads in water or when a fragrance slowly fills a room. It is a fundamental concept in understanding how substances interact and mix at the molecular level, playing a key role in processes like respiration, digestion, and the behavior of gases in different environments.