What property of water explains its solvent abilities for certain substances?

The property of water that explains its solvent abilities for certain substances is polarity. Water molecules are polar, meaning they have a partial positive charge on one side (the hydrogen atoms) and a partial negative charge on the other side (the oxygen atom). This polarity allows water to effectively interact with and dissolve a variety of ionic compounds and polar substances. When an ionic compound, like table salt (sodium chloride), is introduced to water, the positive ends of water molecules surround the negatively charged chloride ions, while the negative ends surround the positively charged sodium ions. This interaction facilitates the separation and dispersion of the ions in solution, demonstrating water's excellent solvent properties for substances that are polar or ionic.

In contrast, hydrophobicity refers to the tendency of nonpolar substances to repel water, which does not aid in the dissolving process. Density describes how closely packed the molecules of a substance are, which does not influence solvent abilities. Viscosity relates to the thickness or resistance to flow of a fluid, which is unrelated to the ability of water to dissolve substances. Understanding the role of polarity is crucial for grasping how water functions as a universal solvent in biological and chemical systems.