What is the term for the process by which a chemical moves through a material by molecular means?

The term for the process by which a chemical moves through a material by molecular means is permeation. Permeation refers to the substance traveling through a barrier or medium at a molecular level, often influenced by concentration gradients and the chemical properties of both the permeant and the material.

In contrast, diffusion typically describes the movement of molecules from an area of higher concentration to an area of lower concentration within a single phase, without requiring a material barrier. Absorption is the process where one substance becomes incorporated into another, often at a bulk level rather than moving through a material. Adsorption refers to the accumulation of molecules on the surface of a solid or liquid, creating a film rather than allowing those molecules to enter the bulk of the material.

Understanding permeation is crucial in hazardous materials management, as it helps technicians assess the protective capabilities of materials encountering hazardous substances.