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
|0 ° C||4.48 g / m³|
|10 ° C||9.40 g / m³|
|20 ° C||17.1 g / m³|
|30 ° C||>30.4 g / m³|
|45 ° C||65.0 g / m³|
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.