======Boiling Cold======


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**Alternative titles:** Butane Boiling, Evaporation Cooling
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====Summary====                   
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====Procedure====  
  - Open a large zipper-lock plastic bag and place the nozzle of a butane spray can inside.  
  - Seal the bag around the nozzle.  
  - Spray butane into the bag for 3–5 seconds, then seal the bag fully. A small amount of liquid butane should collect inside.  
  - Tilt the bag to allow the liquid butane to flow from one corner to another. Observe water vapor condensing on the outside of the bag.  
  - Hold the corner of the bag containing the liquid and observe as it boils vigorously, inflating the bag.



====Links==== 
Boiling Cold - FlinnScientific: 
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📄 Boiling Cold - FlinnScientific: [[https://www.flinnsci.ca/api/library/Download/f9b62167e59a49c2aeabae30748d110e]]\\


====Variations====
  * Compare how quickly condensation forms on the outside of the bag at different room humidities.  
  * Relate this to condensation on cold drinks or sweating pipes.  



====Safety Precautions====
  * Safety goggles, chemical-resistant gloves, and a chemical apron required.  
  * Butane is flammable - keep away from open flames and electrical sparks.  
  * Avoid direct skin contact with liquid butane, which can cause frostbite.  
  * Perform in a well-ventilated area.  
  * Dispose of butane gas safely by venting the bag in a fume hood or well-ventilated space.




====Questions to Consider====
  * Why does liquid butane boil at room temperature when released into the bag? (Because reducing the pressure lowers its boiling point to below room temperature.)  
  * Why does water condense on the outside of the bag? (The butane absorbs heat as it evaporates, cooling the bag below the dew point of the surrounding air.)  
  * How does this experiment illustrate the cooling effect of evaporation? (Evaporation is endothermic, so it removes heat from the surroundings, making objects feel cold.)  
  * Where do we see similar effects in daily life? (Sweating, condensation on cold drinks, air conditioning systems.)