Water is widely distributed on Earth and occurs in various forms and locations. The primary occurrence of water is in the form of vast bodies of water, such as oceans, which cover about 71% of the Earth’s surface. These oceans contain saltwater, making them saline. Freshwater occurs in lakes, rivers, streams, and underground reservoirs known as aquifers. These freshwater sources are vital for drinking water, irrigation, and supporting aquatic ecosystems. Glaciers and ice caps also hold a significant amount of water, mainly in polar regions, and they gradually release water through melting.
Water (H2O) is a compound composed of two hydrogen (H) atoms bonded to one oxygen (O) atom. The ratio of hydrogen to oxygen atoms in water is 2:1. The oxygen atom forms covalent bonds with the two hydrogen atoms through sharing of electrons, resulting in a bent molecular shape. This arrangement gives water its unique properties and allows it to participate in various chemical reactions and biological processes.
The structure of water consists of two hydrogen atoms bonded to one oxygen atom. These bonds are formed through the sharing of electrons, creating covalent bonds. The molecule has a bent or V-shaped geometry due to the arrangement of the atoms. The oxygen atom holds a partial negative charge, while the hydrogen atoms carry partial positive charges, resulting in a polar molecule.
Water can dissolve practically all minerals, water is known as the universal solvent. Water’s capacity to dissolve compounds is due to two distinct qualities of the molecule:
Water is a unique substance due to its polar nature, which arises from the electronegativity difference between oxygen and hydrogen atoms. In a water molecule, oxygen attracts electrons more strongly, creating a partial negative charge near the oxygen atom and partial positive charges near the hydrogen atoms. This polarity gives water distinct properties. It allows water molecules to form hydrogen bonds with one another, leading to high cohesion, surface tension, and the ability to absorb large amounts of heat. Water’s polarity also makes it an excellent solvent for polar and ionic substances, enabling vital biological and chemical processes to occur. The polar nature of water plays a fundamental role in its importance for life and many physical and chemical phenomena observed in our everyday lives.
The oxygen and hydrogen atoms make up the water molecule. One H₂O molecule can create hydrogen bonds with maximum four additional H₂O molecules stacked tetrahedrally around the H₂O molecule due to two O-H bonds and two lone pairs. By establishing hydrogen bonds with various polar non-ionic molecules containing hydroxyl groups (-OH), such as alcohols, organic acids, glucose, sugar, and so on, water is able to dissolve them.