In order to be a liquid on Earth—normally, it's a gas—nitrogen (N2) must reach temperatures below -321° Fahrenheit. Here at the Museum of Science and Industry, we do a program called “Happy Brr-thday!” that routinely involves pouring liquid nitrogen into glass containers that are at room temperature, or approximately 70° F.
That is almost like taking a glass container out of a 400° F oven and dropping it into an ice bath, a level of thermal shock that would crack and shatter most common glass. However, we use a special form of glass known as borosilicate. Glass bakeware, like Pyrex, is usually composed of this type of glass. The secret ingredient making borosilicate glass resistant to thermal shock is right in its name. “Boro” is for boron, which is added to “silicate,” the main component of glass, changing the physical properties of glass in myriad ways.
Most importantly for our purposes, it reduces how much the glass shrinks when it cools (thermal contraction) or expands when it heats up (thermal expansion). Glass undergoes a lot of expansion and contraction when its temperature changes. If you pour a hot liquid into a normal glass container, it first heats only the inside portion of the glass walls. They will begin to expand, while the not-yet-warmed outer layers stay the same size, a difference that creates physical stress within the glass, and ultimately causes it to crack.
Borosilicate glass minimizes these stresses and typically reduces the chance of cracking by limiting the expansion and contraction. These glasses are not invulnerable, though. I would not feel comfortable, say, pulling a borosilicate container out of a 432° F oven and then pouring liquid nitrogen on it. (The glass is good, but I don’t trust it to be that good.)
To see this amazing glass (or the liquid nitrogen) in action, visit MSI and check your map for the next time “Happy Brr-thday!” is happening!
Image Courtesy of Pyrex
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