Fog Machines heat a liquid but the fog isn't hot?

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brightnight1

Joined Jan 13, 2018
91
Fog machines work by heating up a mixture of water and glycerine in a heat exchanger. I'm wondering why the fog that comes out of a fog machine isn't hot even if the nozzle a few hundred degrees fahrenheit. To get from a liquid to a gas state it has to get more energy (heat) right? Does it just get enough energy to get to a gas and then cools from the surrounding air? This has been bothering me for a few days so thought someone would have some good input here.
 

jpanhalt

Joined Jan 18, 2008
11,087
If it were still at its vaporization temperature, it wouldn't be fog, right? That's like asking why clouds aren't at 100 °C. Maybe you can answer why your own mouth can make fog when it is really cold outside?

Edit: You need to lookup the term"vapor pressure." In brief, water exerts a certain vapor pressure (i.e., water gas) that is dependent on temperature. Wikipedia has a nice chart of that relationship. At room temperature (20°C) , which is well below boiling, the pressure of water vapor (a gas) is about 17 torr. It is atmospheric pressure at its boiling point.
 
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