During chemical weathering, when minerals in feldspar change to kaolinite clays, the process is termed as:

The process by which minerals in feldspar change into kaolinite (china clay) is termed Hydration. In this chemical weathering process, minerals chemically absorb water and expand, leading to a change in their chemical composition and physical structure.

• Hydration: According to standard geography texts like G.C. Leong, hydration occurs when water is absorbed by minerals; a classic example is the breakdown of feldspar into kaolin.
• Carbonation: This involves the reaction of minerals with carbonic acid (CO2 dissolved in water). While it often aids the decomposition of granite, the specific conversion to clay via water absorption is categorized as hydration.
• Oxidation: This is the reaction of minerals with oxygen (e.g., the rusting of iron-rich minerals).
• Chelation: This is a biological weathering process involving organic acids from plants or organisms.

Although the process is technically a form of hydrolysis, in the context of standard physical geography options, Hydration is the most appropriate choice.