Steam

water · heat · invisible gas

What steam really is. Steam is water that has been heated so much it transforms into an invisible gas called water vapor. When you see that white mist coming from a boiling pot, that is actually tiny water droplets falling back into the air, not the steam itself.

Heat makes the change. Water turns into steam when it gets hot enough to reach what scientists call the enthalpy of vaporization. This is the special temperature and energy needed to transform liquid water into a gas, which happens at 212 degrees Fahrenheit (100 degrees Celsius) at sea level.

Invisible and visible. True steam is completely invisible because it is just a gas. But when steam cools down slightly in the air, it condenses back into tiny water droplets that form a visible white mist or cloud that we often call steam.

Power from steam. Steam has been used for hundreds of years to power machines like steam engines and generate electricity in power plants. The energy in steam comes from the intense heat that turned the water into gas in the first place.