vann

Vann is the Norwegian Bokmål word for water, the liquid vital to life. The Nynorsk equivalent is vatn. Water has the chemical formula H2O, with a bent molecular structure and polarity, enabling it to dissolve many substances and to form hydrogen bonds. These properties underlie high heat capacity, high surface tension, adhesion and cohesion, and a high heat of vaporization.

Water covers about 71% of Earth's surface, primarily as oceans. Freshwater accounts for a small share, stored in rivers, lakes, groundwater, and ice. The hydrological cycle moves water through evaporation, condensation, precipitation, infiltration, and runoff. Water exists in three main states: liquid, solid (ice), and gas (steam), with phase transitions at 0°C and 100°C at standard pressure.

Humans depend on water for drinking, sanitation, agriculture, industry, and energy. Managing water involves protecting quality, ensuring supply, and maintaining infrastructure. Water quality concerns include pollution, salinization, nutrients, and pathogens. Global challenges include scarcity, drought, and climate change, driving conservation and efficiency improvements and watershed protection.