Waterfasen

Waterfasen, or phases of water, refer to the distinct states of H2O that occur under different temperatures and pressures. The three main phases are solid (ice), liquid (water), and gas (water vapor). Each phase has characteristic molecular arrangements and physical properties: ice forms a crystalline lattice, liquid water is a dense, cohesive fluid, and water vapor is a low-density gas.

Phase transitions connect these states. Melting (freezing as the reverse) occurs near 0°C at standard atmospheric pressure. Vaporization (boiling or evaporation) occurs at 100°C at 1 atm, with condensation as the reverse. Sublimation transfers directly between solid and gas, bypassing the liquid phase. The phase diagram of water shows the boundaries among the phases as temperature and pressure vary; the triple point lies at 0.01°C and 611 pascals, and the critical point at 374.14°C and 22.064 megapascals, above which liquid and gas are indistinguishable (supercritical water).

Ice has multiple crystalline forms, or polymorphs. At atmospheric pressure the common form is ice Ih. Under higher pressures, other forms (ice II, III, V, VI, and others) are stable. Natural ice in snow and glaciers is predominantly Ih. Water’s density behavior is anomalous: ice is less dense than liquid water, so it floats; liquid water has its maximum density near 4°C.

In science and technology, water phases underpin meteorology, hydrology, and industrial processes. Supercritical water, achieved above the critical point, acts as a powerful solvent in certain reactions and waste treatment. Understanding phase behavior helps predict weather, design steam systems, and model planetary environments.