By Aiden Plumbe
Last week in assembly on the 12th of August, we saw what Mr Ansourian claimed to be the second biggest science experiment at Newington. Everyone eagerly watched as Mr Ansourian talked us through the science behind the anticipated experiment before he poured the hot water into the tub of liquid nitrogen.
What is liquid nitrogen?
Liquid nitrogen is, as its name suggests, nitrogen in its liquid state which is achieved by cooling nitrogen gas to extremely low temperatures, normally around -196°C (-321°F). The liquid is colourless and odorless and is widely known for its ability to rapidly freeze items it comes in contact with. It’s likely that you might have played with liquid nitrogen in your science classrooms before and observed up close its fantastic features. Mr Ansourian showed us in assembly with the flower petals that he got Ms Van Arkkels to crush in her hand as well as the balloon that shrunk as the carbon dioxide inside cooled.
As we saw in the assembly’s experiment, liquid nitrogen expands significantly (approximately 695 times its volume) when it transitions to a gas, blending in with the surrounding air. However, this is not a danger or hazard in any way. This is because nitrogen gas actually makes up around 78% of the atmosphere around us and is completely harmless. That means that every time you breathe in, you’re inhaling nitrogen as well as oxygen.
However, it’s time to talk about the actual experiment that resulted in the rapid formation of a cloud.
At normal air pressure, nitrogen becomes a liquid only if the temperature is between –210 and –196°C, which is not overly common, with room temperature being around 20°C. At warmer temperatures though, nitrogen boils and becomes a gas again. The giant liquid nitrogen cloud that we all saw at assembly formed thanks to rapidly cooling water vapour with the liquid nitrogen. The heat from the boiling water rapidly vaporises the water which then comes into contact with the cold liquid nitrogen. As the water vapour cools, it condenses into tiny water droplets, forming an explosive visible cloud that is visually very impressive.
Hopefully, everyone had a fantastic National Science Week and can’t wait for what next year holds.