Superheating occurs when a liquid, such as water, is heated over its boiling point without generating bubbles or boiling visually. This happens in smooth containers, where surface tension prevents bubble development.
In a controlled experiment, distilled water is heated in a microwave to more than 100°C (212°F) without boiling. When disturbed, such as by stirring, the water rapidly boils, resulting in an eruption of steam and bubbles. This demonstrates how superheated liquids can exist and the need for surface tension to prevent nucleation until a disturbance occurs. Superheating can be dangerous since the quick release of steam might result in burns.