Water becomes steam when heated to a temperature of 212 degrees Fahrenheit. That temperature equates to 100 degrees Celsius or 373.15 degrees Kelvin.
Steam is the gaseous state of water. It forms when water boils and is technically invisible, although a person can briefly catch glimpses of it when it mixes with cooler air and forms water droplets in the form of mist.
Steam has many purposes, including electricity generation and soil sterilization. It also serves as a wood and concrete treatment and works in autoclaves to sterilize medical and laboratory equipment with high pressure. In the home, steam cleans floors and carpets and cooks foods.