Which of the following substances is classified as a universal solvent?

Water is classified as a universal solvent because of its unique molecular structure and polarity. The polarity of water molecules means that they have a partial positive charge on one side (due to hydrogen atoms) and a partial negative charge on the other side (due to the oxygen atom). This allows water to interact effectively with a variety of substances, particularly ionic compounds and polar molecules.

When an ionic substance like salt dissolves in water, the positive end of water molecules surrounds the negatively charged ions, while the negative end surrounds the positively charged ions, effectively separating and dispersing them throughout the liquid. This ability to dissolve so many different substances is why water is considered the universal solvent, playing a crucial role in biological systems and chemical reactions.

The other substances—oil, alcohol, and salt—do not possess the same capacity for dissolving a wide range of materials like water does. Oil, being nonpolar, tends to repel water and does not dissolve ionic compounds well. While alcohol can dissolve some substances, it does not exhibit the same extensive solvation power across diverse compounds as water. Salt, although it dissolves well in water, is a solute rather than a solvent. Thus, water's properties firmly establish it as the universal solvent among the choices