The element H2O
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 Amadeo 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.