What is the most important characteristic of water due to its polarity?

The most important characteristic of water due to its polarity is hydrogen bonding. Water molecules are polar, which means 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 leads to the formation of hydrogen bonds between water molecules, where the positive hydrogen atoms of one molecule are attracted to the negative oxygen atoms of another.

Hydrogen bonding is crucial because it contributes to many of water's unique properties, such as its high specific heat capacity, high heat of vaporization, and high surface tension. These attributes play significant roles in environmental processes and biological systems. For instance, the high heat capacity allows water to stabilize temperatures in environments, benefiting living organisms. Hydrogen bonds also help explain water's solvent capabilities, allowing it to dissolve many substances effectively.

In contrast, while viscosity, density, and surface tension are relevant properties of water, they are largely consequences of the polar nature of water and the resulting hydrogen bonds rather than its defining characteristic due to polarity itself.