Water - Definition

Water is a chemical compound with the chemical formula H2O.  A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at temperatures above 0 degree C (273.15 K, 32 degree F) at sea level, but it often co-exists on Earth with its solid state, ice and gaseous state (water vapor or steam).  Water also exists in a liquid crystal state near hydrophobic surfaces.