What is water?

Who discov­ered the water?

It was the chemist Henry Cavendish (1731 – 1810), who discov­ered the compo­si­tion of water, when he exper­i­mented with hydrogen and oxygen and mixed these elements together to create an explo­sion (oxyhy­drogen effect). In 1811 the Italian physi­cian Amedeo Avogadro finally found the H2O formula for water.

Although water has a simple mole­c­ular struc­ture, it never­the­less has unique phys­ical prop­er­ties. It is the only element that exists on our planet in a solid, liquid and gaseous aggre­gate state. It is these special prop­er­ties that make water so fasci­nating and so impor­tant for all crea­tures. Water has 775 times the density of air. This fact causes the ‘buoy­ancy’ effect, which enables us - and most mammals - to swim.

Many substances expand when they are subjected to heat and reduce their density at the same time; conversely, they increase their density when cooled down. When a liquid is cooled, the colder part sinks to the bottom. The freezing process of water is the other way round. Water reaches its maximum density at 4 degrees Celsius, which is exactly 0.999973 kg/l. Ice weighs 0.91 kg/l – which is the reason why icebergs float. This also explains why frozen water bottles explode and why fish can survive in a frozen lake. They live at the bottom where the water is the heav­iest, as the temper­a­ture there is approx­i­mately 4 degrees Celsius.

Water is a very bad heat conductor. This prop­erty is of utmost impor­tance for the global climate. Water can actu­ally store a lot of heat, which it then releases again during the cold season. In the warm season, however, it prevents exces­sive heating. In this way water moder­ates the differ­ences in temper­a­ture.

If one cubic centimetre of water evap­o­rates (at approx. 100 degrees Celsius), its volume expands to 1243 cubic centime­tres (vapour pres­sure) - a process that formed the basis of the construc­tion of the steam engine; this machine even­tu­ally gave rise to the Indus­trial Revo­lu­tion.

The phys­ical and chem­ical prop­er­ties of water make it a universal solvent and means of trans­port, which is inte­grated into all cycles of nature, both micro-​ and macro­scopic. Without water, for example, there would be no circu­la­tion of nitrogen or phos­pho­rous - both essen­tial elements in the bios­phere - as there is no way for the corre­sponding ions to be trans­ported.

Water can dissolve salts and feed these in dissolved form to plants. Plants then use these ions as nutri­ents and release the water they don’t need for their nitrogen metab­o­lism into the atmos­phere. This small water cycle is as impor­tant as the large one - without it, and there­fore without water, there would be no life.

Global Water reserves

With 1.386 million km³ water, our planet blue is a unique place in the universe.

 
Viewed from space the earth is an awe-​inspiring sight: 75% of our planet is covered by water – in liquid, gaseous or frozen form. It is this vital element of life that distin­guishes the Earth from all other planets in our solar system.

 
Yet this apparent abun­dance is decep­tive. Around 97 % of the Earth’s water resources are salt water. A signif­i­cant propor­tion of fresh water reserves is trapped in the polar ice caps and glac­iers and only 0.649% of all water resources can be used for drinking.

 
According to UNO esti­mates, the world’s popu­la­tion is set to increase from approx­i­mately 6.6 billion today to 9.2 billion by 2050. Due to the increasing average per capita consump­tion of water, currently 625m³ per annum, water consump­tion will also grow dispro­por­tion­ately.

 
Glob­ally, more than one billion people have no access to clean drinking water. In 25 years up to 6 billion people will be expe­ri­encing water short­ages because of poor hygiene. Even Europe’s natural water resources are being put under ever-​increasing stress. Water stress arises when the amount of water used exceeds avail­ability. In Austria, only 3% of the total renew­able water supply is extracted annu­ally – we there­fore live in a veri­table water paradise. By contrast, Bulgaria and Belgium, for example, suffer from water stress because they consume 55% and 41% respec­tively per annum of the renew­able water supply.

Sources of Water

The amount of water is constant with approx­i­mately 1386 million m3 of water in perpetual motion. Through solar radi­a­tion, which converts liquid water into water vapour that evap­o­rates from the land and water surface. Humidity stored in the vege­ta­tion is also released into the air (evap­o­tran­spi­ra­tion). With increasing temper­a­ture, the air can absorb increasing amounts of water vapour, which is the basis of the water cycle.

Temper­a­ture Storage capacity of water vapour in the air

The water vapour in the atmos­phere condenses into drops of water. From these, clouds form and even­tu­ally rain will fall. It is vital to our survival that part of the water evap­o­rating from the oceans, again, falls like rain and snow on the earth, filling our rivers, watering the soil and filling the ground­water deposits.