How come nitrogen can stay so cold in all temperatures? I guess it’s not cold when compressed inside the bottle, rather a reaction when turning to gas? But where does the energy from the “room temperature” go?
In: Chemistry
You should ask why liquid nitrogen is so cold. That’s really what you meant to ask. The reason is because we make the nitrogen cold on purpose.
Nitrogen at normal atmosphere is a gas, not a liquid. By squeezing air (which is mostly nitrogen), it heats up. Then, while still squeezed (high pressure), you let it cool down. Then you re-expand the air. Expanding compressed air causes it to lose heat the same way that squeezing it causes it to generate heat. So now you have very cold air. So cold that the nitrogen is liquid at certain pressures.
Why is it liquid? The phase transitions from solid to liquid to gas relate to heat (and also pressure). A hotter thing is easier to make a gas. A cooler thing is easier to make solid. Because heat is just how much energy there is in the material vibrating and moving randomly. Lots of energy = hot = lots of motion = like a gas (each particle is zipping around freely). Low energy = cold = not much motion = staying in place like a solid.
So after going through the process, the nitrogen is cold enough to be liquid.
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