Water Molecule Properties and Hydrogen Bonding

Study Notes

Water molecules are polar, with a partial negative charge near oxygen and a partial positive charge near hydrogen. This polarity leads to unique properties.

Hydrogen bonds form between water molecules, allowing each to bond with up to four others, continuously forming, breaking, and reforming for structure.

Cohesion and Adhesion

Cohesion, caused by hydrogen bonding, is the attraction between similar molecules, enabling water to move up plants via transpiration. Adhesion helps water move through different plant tissues.

Surface Tension

Surface tension is the energy required to increase a liquid's surface area due to cohesive forces, creating an elastic "skin." Water's high surface tension, from hydrogen bonding, allows small objects to float. Water also has a high specific heat, moderating temperatures and resulting in milder coastal climates compared to inland.

Evaporative Cooling

Evaporative cooling involves liquid evaporation, removing heat and influencing Earth’s climate and organism temperature regulation.

Density of Water

The density of water peaks at 4 degrees Celsius, expanding upon cooling to 0 degrees Celsius, preventing solid freezing and supporting aquatic life in winter.

Water as a Solvent

Water, known as the "universal solvent," dissolves ionic compounds due to polar molecules that surround and separate ions. Polar molecules are soluble, while nonpolar molecules are not (hydrophobic). Many biological reactions occur in water, facilitating reactants and products.