Which process involves one substance combining with another?

The correct answer is absorption, which refers to a process where one substance (the absorbate) is taken up or incorporated into another substance (the absorbent) to form a solution or a homogeneous mixture at the molecular level. During absorption, a specific interaction occurs, often involving chemical or physical changes, allowing the absorbate to permeate into the structure of the absorbent.

This process differs from others, such as adsorption, where molecules adhere to the surface of a solid or liquid without being absorbed. Dilution involves reducing the concentration of a substance in a solution, while mixture formation refers to combining substances without specific interactions where one substance is taken into another. Understanding absorption is crucial in hazardous materials contexts, as it impacts how substances behave during a spill or exposure scenario, influencing methods for containment and cleanup.