Water (H2O, HOH) is the most abundant molecule on Earth's surface, constituting about 70% of the planet's surface. In nature it exists in liquid, solid, and gaseous states. It is in dynamic equilibrium between the liquid and gas states at standard temperature and pressure. At room temperature, it is a nearly colorless with a hint of blue, tasteless, and odorless liquid.
Many substances dissolve in water and it is commonly referred to as the universal solvent. Because of this, water in nature and in use is rarely pure and some of its properties may vary slightly from those of the pure substance. However, there are many compounds that are essentially, if not completely, insoluble in water.
Water is the only common substance found naturally in all three common states of matter—for other substances, see chemical properties. Water is essential for life on Earth. Water usually makes up 55% to 78% of the human body.