======Vortex Rings Using Liquid Nitrogen======


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**Materials: **{{$demo.materials_description}}\\
**Difficulty: **{{$demo.difficulty_description}}\\
**Safety: **{{$demo.safety_description}}\\
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**Alternative titles:** Fog Ring Blaster
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====Summary====                   
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====Procedure====  
  - Cut a round hole in the bottom of a plastic garbage bin or in the side of a large cardboard box. The hole should be about one-third the diameter of the base.  
  - Cover the open end of the bin with a sheet of plastic film (such as mattress wrapping) and secure it with tape, leaving it loose enough to push in and out.  
  - Create fog by pouring in hot water then liquid nitrogen. This will generate a thick white vapor cloud.  
  - Hold the vortex gun over the fog so it fills with the nitrogen fog.  
  - Pull the plastic sheet back slightly and then push it inward to blast air through the hole.  
  - Observe the visible toroidal vortex ring shooting out across the room.  
  - Repeat, aiming at lightweight targets like paper cups or tissue balls.  




====Links==== 
Smoke (fog) rings (vortices) with liquid nitrogen - MrGrodskiChemistry: 
{{youtube>F2HwLbDZuFM?}}\\

📄 Toroidal vortex gun - ABC Science: [[https://www.abc.net.au/science/articles/2012/07/17/3546850.htm?site=12science&]]\\



====Variations====
  * Use different size holes to compare vortex size and speed.  
  * Shine a laser or flashlight through the fog rings to highlight their shape.  
  * Try gentle taps for slow-moving rings or firm hits for powerful blasts.  




====Safety Precautions====
  * Safety glasses required.  
  * Wear cryogenic gloves when handling liquid nitrogen.  
  * Use liquid nitrogen only in a well-ventilated space.  
  * Keep hot water containers stable to prevent spills.  
  * Do not place liquid nitrogen directly in the vortex gun - only use the fog it produces.  
  * Ensure smoke detectors are isolated if doing this indoors, as nitrogen fog may trigger alarms.  





====Questions to Consider====
  * Why does the fog make the vortex rings visible when air vortices are usually invisible?  
  * What forces hold a toroidal vortex together as it travels?  
  * How does this relate to the kinetic theory of gases and air pressure?  
  * Where else in nature do toroidal vortices appear (e.g., volcanoes, underwater bubble rings, mushroom clouds)?  
  * Why does the vortex stay stable for so long instead of dissipating immediately?