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Q: Vaporization of Water with Pressure Differential ( No Answer,   3 Comments )
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 Subject: Vaporization of Water with Pressure Differential Category: Science > Physics Asked by: megahog-ga List Price: \$5.00 Posted: 03 May 2006 13:52 PDT Expires: 04 May 2006 14:17 PDT Question ID: 725202
 ```Can the enthalpy of vaportization (latent heat of vaporization) be "overcome" for saturated liquid water at 1000 kPa by creating a pressure differential of 300 kPa via a pressure control valve? I know up to this point that energy must be put into the water to vaporize, but can a change in pressure vaporize the water?```
 There is no answer at this time.

 ```I remember in my high school chemistry class the teacher did a demonstration. She put water in a beaker and boiled it, not by heating it but by putting it in a machine that created a vaccuum. When the air pressure inside was low enough, the water boiled at room temperature.```
 ```As Ansel says, you can vaporize the water by reducing the pressure below the vapor pressure at the water's temperature. You still need to supply the heat of vaporization. If there is no source of heat, the water will cool down as it vaporizes. This is how refrigerators work. Jim```
 ```It sounds as if you are after what I call a 'heat knife' Divide a set level of temperature into heat+ and heat- (cold) I've been assured that it is not possible, which makes me suspect that it is. We are basking in potential energy, kicking a rock of a mountain takes little effort, but the avelanche at the bottom is pretty powerful.```