Properties of water

Water’s properties arise from its bent, polar molecules and their hydrogen bonding. These interactions shape its phase behavior, density, heat capacity, and ability to dissolve many substances.

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Water molecule: A bent molecule containing two hydrogen atoms bonded to one oxygen atom. Its shape and charge distribution produce water’s polarity.
Water density: The mass of water per unit volume, which varies with temperature and pressure. Its temperature dependence includes the distinctive density maximum near 4 °C.
Aqueous solution: A solution in which water is the solvent. Water’s polarity and ion-stabilizing ability make aqueous solutions central to chemistry and biology.
Ammonia: A polar molecule composed of one nitrogen atom bonded to three hydrogen atoms. Like water, ammonia forms hydrogen bonds, but its different structure produces different bulk properties.
Hydrogen bond: An attractive interaction involving a hydrogen atom bonded to an electronegative atom and another electronegative atom. These interactions connect neighboring water molecules and drive many of water’s distinctive properties.
Specific heat capacity: The heat required to raise the temperature of a unit mass of a substance by one degree. Water’s high value explains why it warms and cools slowly.
Hydration shell: A layer of water molecules organized around a dissolved ion or polar molecule. Water’s charge distribution creates structured surroundings for dissolved substances.
Hydrogen fluoride: A polar diatomic molecule consisting of hydrogen bonded to fluorine. Its strong hydrogen bonding highlights how molecular geometry and bonding affect liquid properties.
Water polarity: The uneven distribution of electrical charge across a water molecule. Its partial charges let water interact strongly with ions and other polar molecules.
Heat of vaporization: The energy required to convert a liquid into vapor at constant pressure. Water requires substantial energy to evaporate because molecules must separate from hydrogen bonds.