A Level Chemistry OCR Practice Exam 2025 - Free Chemistry Practice Questions and Study Guide

The process of adsorption is indeed the adherence of a gas, liquid, or solute to a solid surface. This phenomenon occurs when molecules of a substance from one phase (such as gas or liquid) come into contact with a solid surface and are held there through intermolecular forces, forming a film on the solid.

Adsorption is fundamental in various scientific fields and applications, including catalysis, water purification, and gas sensing. In contrast, other processes listed, such as the formation of gas bubbles in a liquid or the release of a gas from a liquid solution, involve different mechanisms not related to the interaction of molecules with solid surfaces. Additionally, the chemical reaction between two solids suggests a more complex interaction where new substances are formed, which is not the focus of adsorption. Therefore, the correct understanding of adsorption pertains to the specific interaction of substances with solid surfaces, solidifying option C as the appropriate choice.