What term describes a substance that forms a shell of hydration when it is soluble in water?

The term that describes a substance capable of forming a shell of hydration when soluble in water is hydrophilic. Hydrophilic substances have an affinity for water and interact favorably with it, often allowing water molecules to surround and solvate them. This property is a result of polar or charged functional groups within these substances, which can form hydrogen bonds with water molecules. When a hydrophilic substance dissolves in water, it creates a shell of hydration—essentially a layer of water molecules that are structured around the solute.

In contrast, hydrophobic substances do not have a strong interaction with water and tend to repel it; they do not form hydration shells and instead aggregate in an aqueous environment. Amphipathic molecules contain both hydrophilic and hydrophobic parts, allowing them to interact with both water and nonpolar substances but do not solely describe those that can form hydration shells. Nonpolar substances, lacking charge or polarity, interact minimally with water and similarly do not form hydration shells. Thus, hydrophilic is the term that most accurately defines substances that solvate in water by forming a hydration layer.