what is water?

"H2O" and "HOH" redirect here. For other uses, see H2O (disambiguation)and HOH (disambiguation). This article is about general aspects of water. For a detailed discussion of its physical and chemical properties, see Properties of water. For other uses, see Water (disambiguation). Water in three states: liquid, solid ( ice), and gas (invisible water vaporin the air). Cloudsare accumulations of water droplets, condensedfrom vapor-saturated air. Play media Video demonstrating states of water present in domestic life. Wateris a transparent fluid which forms the world's streams, lakes, oceans and rain, and is the major constituent of the fluids of living things. As a chemical compound, a water moleculecontains one oxygenand two hydrogen atomsthat are connected by covalent bonds. Water is a liquidat standard ambient temperature and pressure, but it often co-exists on Earthwith its solidstate, ice; and gaseousstate, steam( water vapor). Water covers 71% of the Earth's surface. [ 1 ]It is vital for all known forms of life. On Earth, 96.5% of the planet's water is found in seas and oceans, 1.7% in groundwater, 1.7% in glaciers and the ice caps of Antarctica and Greenland, a small fraction in other large water bodies, and 0.001% in the airas vapor, clouds(formed of solid and liquid water particles suspended in air), and precipitation. [ 2 ] [ 3 ]Only 2.5% of the Earth's water is freshwater, and 98.8% of that water is in ice and groundwater. Less than 0.3% of all freshwater is in rivers, lakes, and the atmosphere, and an even smaller amount of the Earth's freshwater (0.003%) is contained within biological bodies and manufactured products. [ 2 ] Water on Earth moves continually through the water cycleof evaporationand transpiration( evapotranspiration), condensation, precipitation, and runoff, usually reaching the sea. Evaporation and transpiration contribute to the precipitation over land. Water used in the production of a good or service is known as virtual water. Safe drinking wateris essential to humans and other lifeforms even though it provides no caloriesororganic nutrients . ... organic nutrients. Access to safe drinking water has improved over the last decades in almost every part of the world, but approximately one billion people still lack access to safe water and over 2.5 billion lack access to adequate sanitation. [ 4 ]There is a clear correlation between access to safe water and gross domestic product per capita. [ 5 ]However, some observers have estimated that by 2025 more than half of the world populationwill be facing water-based vulnerability. [ 6 ]A report, issued in November 2009, suggests that by 2030, in some developing regions of the world, water demand will exceed supply by 50%. [ 7 ]Water plays an important role in the world economy, as it functions as a solventfor a wide variety of chemical substances and facilitates industrial cooling and transportation. Approximately 70% of the fresh water used by humans goes to agriculture. [ 8