Definition: Water is a transparent, tasteless, odorless, and nearly colorless chemical substance essential for all known forms of life. It is composed of two hydrogen atoms bonded to one oxygen atom, with the chemical formula H₂O. Water covers about 71% of the Earth's surface and exists in liquid, solid, and gas states.
## Composition and Properties
Water consists of two hydrogen atoms covalently bonded to one oxygen atom. It has unique physical properties, including a high specific heat capacity, surface tension, and the ability to dissolve many substances, making it a universal solvent. Water exists naturally in three states: liquid, solid (ice), and gas (water vapor).
## Distribution on Earth
Approximately 71% of the Earth’s surface is covered by water, primarily in oceans, seas, rivers, lakes, and glaciers. Freshwater constitutes about 2.5% of total water, mostly trapped in glaciers and underground aquifers, with only a small fraction readily accessible for human use.
## Biological Importance
Water is vital for all known living organisms. It participates in biochemical reactions, regulates temperature, transports nutrients and waste, and provides a medium for cellular processes. Its availability is crucial for agriculture, industry, and human consumption.
## Environmental and Human Use
Water resources are managed for drinking, sanitation, agriculture, energy production, and recreation. Pollution and overuse pose significant challenges to maintaining clean and sustainable water supplies worldwide.