Liquid nitrogen

Liquid nitrogen is nitrogen cooled below its boiling point, about −196 °C at atmospheric pressure. It is a colorless cryogenic liquid that rapidly boils into nitrogen gas when warmed.

Liquid–vapor phase transition: A change between liquid and gaseous states as temperature or pressure changes. Liquid nitrogen boils when heat drives it across this phase boundary.
Cryopreservation: The preservation of cells, tissues, or other biological materials at very low temperatures. Liquid nitrogen can preserve biological samples by greatly slowing molecular activity.
Nitrogen: A chemical element with atomic number 7 that makes up most of Earth’s atmosphere as N₂. Liquid nitrogen is the condensed form of this atmospheric gas.
Liquid helium: Helium cooled into a liquid, commonly used to reach temperatures far below those attainable with liquid nitrogen. It serves applications requiring colder temperatures, such as many superconducting magnets.
Oxygen-deficiency hazard: The danger posed when oxygen concentration falls below levels needed for safe breathing. Rapid evaporation can displace enough room air to cause unconsciousness or death.
Latent heat of vaporization: The energy absorbed per unit mass when a liquid becomes a gas without changing temperature. Vaporization absorbs heat, enabling liquid nitrogen to cool nearby materials.
Cryotherapy: The use of extreme cold to destroy or treat abnormal tissue. Clinicians use liquid nitrogen to freeze selected skin lesions.
Fractional distillation of air: An industrial process that separates air’s components by cooling and exploiting their different boiling points. Most commercial liquid nitrogen is separated from liquefied air this way.
Liquid oxygen: Oxygen cooled into a pale-blue liquid that strongly supports combustion. Unlike nitrogen, it is an oxidizer and can make materials ignite more readily.
Pressure vessel: A container designed to hold gases or liquids at pressures different from ambient pressure. Sealing liquid nitrogen in a rigid vessel can cause dangerous pressure buildup.

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