Liquid nitrogen's temperature can be readily reduced to its freezing point of -210 °C by placing it in a vacuum chamber pumped by a vacuum pump.
While liquid nitrogen is already extremely cold, naturally boiling at around -196 °C (77 K) at standard atmospheric pressure, its temperature can be lowered even further. This additional cooling down to its freezing point is achieved by reducing the pressure above the liquid.
Reducing Liquid Nitrogen Temperature to its Freezing Point
Lowering the pressure above a liquid causes its boiling point (and subsequently its freezing point) to decrease. By placing liquid nitrogen in a sealed chamber and using a vacuum pump to remove gas molecules, the pressure is significantly lowered. This process forces the liquid to boil more vigorously at a lower temperature. As the liquid boils, it removes heat from the remaining liquid, further cooling it until it reaches its freezing point under the reduced pressure conditions.
This technique is a practical application of the principle that the boiling point of a substance is dependent on the surrounding pressure.
Key Temperature Points
Here are the key temperatures associated with liquid nitrogen, as mentioned in the reference:
| State Transition | Temperature (°C) | Temperature (°F) | Temperature (K) |
|---|---|---|---|
| Freezing Point | -210 | -346 | 63 |
- Reference: Liquid nitrogen - Wikipedia
By using a vacuum pump to lower the pressure above the liquid, you can achieve temperatures down to approximately 63 K, causing the liquid nitrogen to freeze.
