Insights Blog
-- Browse All Articles --
Physics Articles
Physics Tutorials
Physics Guides
Physics FAQ
Math Articles
Math Tutorials
Math Guides
Math FAQ
Education Articles
Education Guides
Bio/Chem Articles
Technology Guides
Computer Science Tutorials
Forums
Trending
Featured Threads
Log in
Register
What's new
Search
Search
Search titles only
By:
Menu
Log in
Register
Navigation
More options
Contact us
Close Menu
JavaScript is disabled. For a better experience, please enable JavaScript in your browser before proceeding.
You are using an out of date browser. It may not display this or other websites correctly.
You should upgrade or use an
alternative browser
.
Forums
Physics
Classical Physics
Thermodynamics
How does evaporation generate cooling? Swamp coolers edition
Reply to thread
Message
[QUOTE="Ken G, post: 6854015, member: 116697"] You are correct that it takes a lot more energy to make the water into vapor than it did to get it to 100 C, this is called the "heat of vaporization" and is 540 calories per gram (and it takes only 75 calories per gram to go from room temperature at 25 C to 100 C, which is a good thing because this means you can keep the water boiling for about 7 times longer than it takes to heat up, before it all boils off). The reason is, to increase temperature, you only have to add kinetic energy to the water molecules, you don't have to pull them away from each other. They attract each other (due to electric attraction when the positive side of one molecule approaches the negative side of another), so it takes a lot of energy to pull them apart. You can think of it like, if you had a ball hanging from a rubber band, you could easily put energy into the ball to make it move up and down, but if you wanted to actually break the rubber band, that would take a lot more energy. When you sweat, you cool yourself, though your temperature is way below 100 C because it is only the fastest moving water molecules that have enough kinetic energy to break away from the attraction of the other molecules. So this removes energy from the rest of the molecules, because you are selecting the ones with the highest energy. It would be like if every millionaire on Earth left to go live on Mars, not only would we have a lot less money left behind on Earth, we'd also have less average money per person. Less average kinetic energy per particle means lower temperature. Yes, condensation does release heat. In fact, this is the primary mechanism for energizing thunderstorms. When a plane flies through a thunderstorm, it notices that there are very high winds in there, which are powered by the heat released by condensing water vapor into water droplets. I don't know about the practical applications of this for house heating (the problem would finding enough water vapor), but it is certainly important in thunderstorms! [/QUOTE]
Insert quotes…
Post reply
Forums
Physics
Classical Physics
Thermodynamics
How does evaporation generate cooling? Swamp coolers edition
Back
Top