Liquid Nitrogen Fog

Here's a quick way to make a miniature fog bank...

We took an 800 ml beaker of liquid nitrogen outside on a cold winter morning, tossed it up into the air, and recorded the whole thing at 1/10th normal speed (i.e., 300 frames-per-second). As you can see from the video below, the results produced a small tule fog bank as the liquid nitrogen rapidly condensed the moisture out of the air.

Creating a Small, and Very Cold, Fog Bank in Slow Motion 

So, what's going on here???

First off, liquid nitrogen is cold - really cold... Liquid nitrogen boils at 321 degrees Fahrenheit below zero (i.e., -321 °F) and as can be seen in the photo below rapidly coats the outside of the beaker in a thick layer of ice.

 

A Very Cold Beaker...

 

From the viewpoint of the liquid nitrogen, a cold winter's morning is a blisteringly-hot day. Our roughly 50 °F blacktop parking lot might as well be a hot frying pan as far as the nitrogen is concerned. The droplets instantly freeze the moisture out of the surrounding air, and rapidly evaporate the liquid upon contact with the ground, creating a very cold white fog that rolls along the ground. A good example of this is shown in the photo below.

 

Falling Liquid Nitrogen Freezing the Surrounding Air

 

The air surrounding the liquid nitrogen droplets is so cold, in fact, that you can easily see the denser air falling towards the ground (and also the fact that atmospheric air is roughly 78% nitrogen anyway, so there is very little buoyant force present). 

Pretty cool - literally...