A process by which one substance combines with a second substance is

• A. Absorption.
• B. Combination.
• C. Mixture.
• D. Solution.

Answer: (A)

Absorption is the process where one substance enters into another and becomes part of its interior, effectively taking up space within the absorbing material. In hazmat contexts, this describes how a contaminant is drawn into and held by an absorber—into the bulk of the material or its pores—so the two substances are taken up together rather than just sitting side by side. This helps explain why absorption is used to describe containment of spills or vapors by absorbent materials, where the contaminant is incorporated into the absorber itself.

This differs from a simple mixture, where substances are merely blended without one being taken into the interior of the other, and from a solution, where a solute dissolves in a solvent to form a uniform phase but not necessarily being absorbed into the absorber’s bulk. It also differs from an overarching “combination” idea, which can imply a reaction or bond but doesn’t specifically emphasize uptake into a host material. An absorbing material soaking up liquid illustrates absorption by showing the contaminant becoming part of the absorber’s structure rather than just mingling with it.