Water ($\text{H}_2\text{O}$) possesses an asymmetric structure that gives rise to its unique properties. The oxygen atom attracts shared electrons more strongly than the two hydrogen atoms, creating a significant separation of electric charge within the molecule. This uneven charge distribution results in molecular polarity, where the oxygen end carries a slight negative charge and the hydrogen ends carry slight positive charges, making water a dipole molecule. This polarity allows neighboring water molecules to form weak attractions called hydrogen bonds, linking them into a complex, dynamic network. Imagining water as a nonpolar molecule means removing this fundamental charge separation and the resulting intermolecular forces.
A Gaseous World
The absence of molecular polarity would immediately dismantle the cohesive forces that hold liquid water together. Hydrogen bonds, which stem directly from water’s polarity, are responsible for water’s unusually high boiling and freezing points. Without these strong intermolecular attractions, water molecules would only interact through much weaker forces, similar to those found in nonpolar molecules like methane. Consequently, nonpolar water would exist as a gas at typical Earth temperatures, likely possessing a boiling point far below $0^\circ\text{C}$.
The vast oceans, lakes, and rivers would instantly vaporize, creating a planet-wide, high-pressure, water-vapor atmosphere. The loss of polarity would also eliminate the density anomaly of water, where ice is less dense than its liquid form. Polar water’s hydrogen bonds force molecules into an open, crystalline lattice structure upon freezing. Nonpolar water would behave like most other substances, with the solid form sinking in the liquid.
This eliminates the insulating layer of floating ice that protects aquatic life in cold climates. Furthermore, the high surface tension, which allows water to form droplets, and capillary action in plants would vanish, as both phenomena rely on the strong cohesive pull of hydrogen bonds.
Reversed Solubility
The polarity of current water makes it an exceptional solvent for other polar and charged substances, summarized by the rule “like dissolves like.” Polar water dissolves salts and sugars by surrounding the charged ions or polar regions of the solute molecules, pulling them into solution. If water were nonpolar, this solvent capability would be entirely inverted.
Nonpolar water would readily mix with nonpolar compounds, such as oils, fats, and various hydrocarbons, which are currently immiscible with water. Substances like gasoline and cooking oil would become miscible, forming homogeneous mixtures with the nonpolar water.
Conversely, nonpolar water would be incapable of dissolving its current primary solutes. Ionic compounds, including biological salts and necessary geological minerals, would be insoluble, precipitating out of solution. This also applies to polar organic molecules like glucose and amino acids, which rely on water’s polarity to dissolve and be transported. The chemical environment would be dictated by nonpolar interactions, rendering many of the planet’s existing chemical cycles impossible.
Planetary Heat Regulation Failure
The unique ability of polar water to form a vast network of hydrogen bonds provides it with an exceptionally high specific heat capacity. This means liquid water can absorb or release large amounts of thermal energy with only a modest change in temperature. This property is a major stabilizing force for global climate, moderating temperature extremes near large bodies of water.
Nonpolar water would lose this thermal stability, resulting in a significantly lower specific heat capacity. The atmospheric water vapor would heat up and cool down rapidly in response to sunlight and planetary rotation, leading to extreme and volatile temperature swings. Without the temperature-buffering effect of liquid oceans, global temperatures would fluctuate wildly between scorching daytime highs and frigid nighttime lows, making stable climate zones impossible.
The planet’s hydrological cycle would be severely disrupted by this thermal instability and the gaseous state of water. The lack of stable liquid oceans means there would be no consistent reservoir for evaporation and condensation. Rain, if it occurred, would be an unpredictable atmospheric event rather than a stable, cyclical process, preventing consistent weather patterns and freshwater distribution. The absence of a large, liquid thermal sink would also drastically affect atmospheric pressure and circulation, turning the planet into a chaotic system defined by thermal extremes.
The End of Carbon-Based Biology
The biological machinery of carbon-based life is intimately dependent on the polar nature of water. Water acts as the medium for all cellular chemical reactions and is deeply integrated into the structures of biological macromolecules. The ability of water to force nonpolar molecules together is the driving force behind the formation of cell membranes.
Cell membranes are composed of lipid bilayers, which form because the nonpolar tails of the lipid molecules are repelled by polar water, spontaneously arranging themselves into a protective, enclosed layer. Without polar water, this fundamental self-assembly would not occur, and the structural integrity of all cells would collapse.
Similarly, the intricate three-dimensional shapes of proteins and DNA are stabilized by their interactions with polar water. Water’s polarity dictates which parts of a protein fold inward (hydrophobic residues) and which parts face outward (hydrophilic residues), a process known as hydrophobic collapse. Without water acting as a specific polar solvent, proteins would fail to fold into the precise shapes required for their function as enzymes, and the stable double-helix structure of DNA, which relies on hydrogen bonds, would be compromised. The necessary chemical reactions and transport mechanisms that define metabolism would cease, making carbon-based life chemically and structurally impossible.