Nitrogen makes up almost 80% of the atmosphere by volume. Gas can be cooled down and pressurized to make liquid nitrogen. Liquid nitrogen is cold, inert, colorless, odorless, non-corrosive, nonflammable liquefied gas with a temperature of - 196 °C/- 321 °F. It immediately boils in contact with a warmer object, so basically any object on room temperature. As it causes frostbite on any tissue use of cryogenic gloves as well as goggles is recommended.
Look inside the Dewar flask and notice the bubbling liquid. Liquid nitrogen boils at room temperature.
The addition of liquid nitrogen to a container with hot water leads to rapid nitrogen evaporation, caused by its sudden heating. The temperature difference is almost 300°. Water vapor above the container with the hot water immediately condenses in air. Instead of rising like steam, the water vapor sinks though. When the water in the air is exposed to the extremely low temperature the water molecules freeze forming an aerosol - observed as fog. The water that remains in the metal container is considerably colder than in the beginning, and sometimes it freezes.