UPSC CDS 2 2022 GK Paper

Concept:Hydration is the process where minerals chemically absorb water, causing them to expand and generate internal stress in rocks.Explanation:During hydration, water molecules split into $H^+$ and $OH^-$ ions and become rigidly attached to the atoms of a mineral.This addition of water increases the volume of the mineral, creating physical stresses within the rock.For example, iron oxides ($\mathrm{Fe}_2\mathrm{O}_3$) convert to iron hydroxides ($\mathrm{Fe}(\mathrm{OH})_3$), which occupy a larger volume.Hydration is reversible — repeated cycles of wetting and drying cause fatigue and eventually disintegration of the rock.The expansion leads to physical weathering effects like exfoliation and granular disintegration.In contrast, hydrolysis consumes water to break down minerals, oxidation combines minerals with oxygen, and carbonation involves carbon dioxide forming carbonic acid — none of these primarily cause expansion from water uptake.Answer:Hydration