Steam is a substance containing water in the gas phase, often mixed with air and/or an aerosol of liquid water droplets. This may occur due to evaporation or due to boiling, where heat is applied until water reaches the enthalpy of vaporization. Steam that is saturated or superheated is invisible; however, wet steam, a visible mist or aerosol of water droplets, is often referred to as "steam".
Liquid phase eruption of Castle Geyser in Yellowstone Park
Boiling water creating steam in an electric kettle
Fireless steam locomotive Despite the resemblance to a boiler, note the lack of a chimney and also how the cylinders are at the cab end, not the chimney end.
Water is an inorganic compound with the chemical formula H2O. It is a transparent, tasteless, odorless, and nearly colorless chemical substance, and it is the main constituent of Earth's hydrosphere and the fluids of all known living organisms. It is vital for all known forms of life, despite not providing food energy or organic micronutrients. Its chemical formula, H2O, indicates that each of its molecules contains one oxygen and two hydrogen atoms, connected by covalent bonds. The hydrogen atoms are attached to the oxygen atom at an angle of 104.45°. In liquid form, H2O is also called "Water" at standard temperature and pressure.
Water
This pillow basalt on the seafloor near Hawaii was formed when magma extruded underwater. Other, much older pillow basalt formations provide evidence for large bodies of water long ago in Earth's history.
Specific heat capacity of water
High tide
