Freezing nitrogen in a vacuum creates this exotic material
It’s time you gave nitrogen a second thought
It’s used to cool computers, remove warts, and to prepare food
It boils at -320.8 degrees and freezes at -346 degrees
The Food and Drug Administration has expressed concern about its use in preparing food
Liquid nitrogen is an amazing substance. Let’s get the mundane out of the way. Nitrogen is a nonmetal chemical element. It has the chemical symbol N, and the atomic number “7”. Its stable core typically contains 14 nucleons (seven protons and seven neutrons). It has five electrons in its outer shell. It was first discovered and isolated by Scottish physician Daniel Rutherford in 1772.
Eight things that will shock and surprise your friends and family about nitrogen
Yeah, yeah… you remember all of that from chemistry class. But we said “amazing.” Why do we say that, and what makes it so? Glad that you asked. Consider these things:
- Earth’s atmosphere is more than 78 percent nitrogen
- Nitrogen’s boiling point is -196 degrees Celsius, or -320.8 degrees Fahrenheit. Yes, that’s right – its boiling point!
- It’s used as a coolant for computers
- It’s used to remove unwanted skin, warts, and pre-cancerous cells
- It can instantaneously freeze and shatter nearly anything it touches, including the human body
- Liquid nitrogen itself doesn’t freeze until it reaches -346 degrees Fahrenheit
- It produces groovy vapor or fog when exposed to air
- Avant-garde restaurateurs like Heston Blumenthal have used it to make nitro-scrambled eggs, bacon ice cream, and nitro-poached aperitifs at The Fat Duck
Impressed yet? Impressed or not, have you ever wondered…
What happens when you freeze nitrogen in a vacuum?
Amazing as liquid nitrogen is in a liquid state, freezing it inside a vacuum reveals a remarkable chemical structure. Let’s explore it with help from chefsteps.com.
When a liquid is placed inside a vacuum chamber, the boiling point of that liquid – any liquid – drops. Why? Because — WARNING: more chemistry class flashbacks — the boiling point of any liquid is the temperature at which the pressure of evaporating liquid equals the ambient pressure. So what?
Well, as the pressure in the chamber falls, the liquid nitrogen boils more vigorously because it’s now warmer than its new boiling point. The faster it boils, the faster it evaporates, which leaves the nitrogen that is left behind even colder. How cold? Well, so cold, that it is converted into a glassy solid.
That glassy substance is the sign of something neat, though. It’s a sign that the liquid cooled so quickly that the atoms had no time to organize themselves into neat crystal forms. Enjoy it while it lasts, though, because it doesn’t last long.
With one slight shift of a random atom, within mere seconds, a chain reaction starts and transforms the atoms into a hexagonal lattice. Say what? Think of a snowflake-like structure that is 346 degrees below zero. Brr.
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And that is what happens when you freeze nitrogen in a vacuum. Just your basic boiling-cooling-solidifying-glassifying-hexagonicalation… to coin a phrase.
Is liquid nitrogen safe?
It’s not toxic, but it’s so cold that it shouldn’t come into contact with skin or internal organs. Handling it requires significant and careful preparation and equipment. Which begs the question, is it safe to eat foods that have been prepared with it at The Fat Duck and elsewhere? The Food and Drug Administration, in August 2018, expressed concern:
Liquid nitrogen, although non-toxic, can cause severe damage to skin and internal organs if mishandled or accidently ingested due to the extremely low temperatures it can maintain. Inhaling the vapor released by a food or drink prepared by adding liquid nitrogen immediately before consumption may also cause breathing difficulty, especially among individuals with asthma.
As amazing as nitrogen is — frozen or liquid — it requires care and caution when handling and using it. Leave it to the pros, whether chemists or chefs.
A deeper dive – Related reading from the 101:
Foods prepared with liquid nitrogen might be one clue, but it’s not the only one to watch for.
Food fads come and go, and – popular or not – are not always safe. The Food and Drug Administration is on guard.