What property of water allows it to dissolve many ionic and polar substances?

The property of water that allows it to dissolve many ionic and polar substances is its polarity. Water molecules are polar due to the difference in electronegativity between the oxygen and hydrogen atoms. This results in a partial negative charge near the oxygen atom and a partial positive charge near the hydrogen atoms.

When ionic or polar substances are introduced to water, the positive ends of the water molecules are attracted to the negatively charged ions, while the negative ends are attracted to the positively charged ions. This interaction helps to pull the ionic compounds apart into their constituent ions, effectively dissolving them in the process. Additionally, polar substances can form hydrogen bonds or dipole-dipole interactions with water molecules, which enhances solubility.

In contrast, high surface tension, viscosity, and density are properties of water that do not directly contribute to its ability to act as a solvent for ionic and polar substances. Surface tension is more related to the cohesive forces between water molecules, viscosity refers to the thickness or resistance to flow of water, and density pertains to the mass of water per unit volume. These properties, while important in other contexts, do not explain the solvent capabilities of water.