The article "Plasmas Show Promise As Next Step For Accelerators" (Tom Abate, The Scientist, Nov. 23, 1992, page 15) contained the sentence "He knew that a laser fired into a cloud of hydrogen-- chosen for its simple atomic structure--would superheat the gas, stripping the electrons from their nuclei and thus creating a plasma."

The word superheat has a specific thermodynamic meaning. It means to raise the temperature of a substance above a transition temperature without the equilibrium phase forming. It does not mean to "get really hot."

Superheating is similar in concept to supercooling, in which a liquid is cooled below its freezing point without the separation of the solid phase. Common materials can be supercooled. Very pure water can be cooled far below 0 C without it turning into ice. (The slightest disturbance, however, will trigger instant ice formation.) Superheating of water or metals does not ordinarily occur because...

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