What is the term for the movement of a substance from high concentration to low concentration?

The movement of a substance from an area of high concentration to an area of low concentration is referred to as diffusion. This process occurs spontaneously and is driven by the random motion of particles, resulting in the even distribution of molecules throughout a given space. Diffusion is a fundamental concept in various scientific disciplines, including biology and chemistry, and plays a critical role in processes such as the exchange of gases in the lungs and the transport of nutrients and waste products in living organisms.

Understanding diffusion is essential because it is a passive transport mechanism that does not require energy input, differentiating it from other processes like osmosis, which specifically involves the movement of water through a selectively permeable membrane, and filtration, which involves the movement of substances across a barrier, often driven by pressure. Suspension refers to a heterogeneous mixture where fine solid particles are dispersed in a liquid or gas, but it is not related to the concept of concentration gradient movement. Thus, diffusion accurately captures the essence of the described process.