What describes the breakdown of chemicals by a chemical reaction with water?

The correct answer is indeed the breakdown of chemicals by a chemical reaction with water, which is defined as chemical degradation. This process occurs when a substance undergoes a chemical transformation in the presence of water, often leading to the formation of different chemical compounds. Water can act as a solvent or a reactant, facilitating reactions that break down the original chemicals into smaller molecules or different substances.

Understanding chemical degradation is important for recognizing how pesticides and other chemicals can break down in the environment, which can impact their effectiveness and potential hazards. This process is critical for evaluating the longevity and safety of chemical residues in agricultural practices.

In contrast, the other choices refer to different processes. Microbial action involves the breakdown of substances by microorganisms, such as bacteria and fungi, rather than a direct chemical reaction with water. Photodegradation pertains to the breakdown of compounds due to light (usually sunlight) exposure, and volatility refers to the tendency of a substance to vaporize or become gaseous at room temperature, which is unrelated to chemical reactions with water. Understanding these distinctions helps clarify the correct definition associated with the breakdown of chemicals in water.