How does steam work? — SS, Nairobi, Kenya
Steam is the gaseous form of water. When the water molecules in liquid or solid water have enough thermal energy, they can break free of one another and become independent particles. Even at room temperature, the air you are breathing is several percent water molecules. But at higher temperatures, the rate at which water molecules leave the surface of solid or liquid water increases so much that these water molecules can form a dense, high-pressure gas. This gas is called steam.