Can’t clarify the question in one sentence. I’m trying to understand this phenomenon: If you place a rubber band against your upper lip, a pretty sensitive thermometer, and stretch the rubber band, you’ll feel it get a little warm. And if you relax the rubber band, you’ll feel it get cool. I’m thinking that the energy of stretching it is converted into some sort of internal friction that warms it up. But what’s happening when it goes back to its original size and shape? Why does it draw heat from your lip? Why does it feel cool?
Funny you should ask. I was just reading something about this last night. It has something to do with something called Gibb’s free energy, which despite its name, is not the title of a Bee Gee’s album. Good luck chewing through this crap—it made my head asplode. I had to just take a Tylenol and a tequila and go to bed whimpering.
It happens because “the world is a dynamic mess of jiggling things”
as it stretches it becomes more orderly, things will give off heat when doing so, when it contracts the opposite happens.
ZOWIE!!! I feel as if Richard Feynman just explained something to ME! What an honor. (and what a great find, 74westy. Thanks!)
Has anyone ever exploited this effect to make a refrigerator with a rubber band-based coolant cycle?
Total fluke. It just happens that I watched that in the last week or so. I was quite surprised when you came up with such an insanely great question that I could find an answer to.
And yes, I know what it’s like when Feynman shows up an explains something very subtle to me in a way that makes it very clear. Watch the whole series.
Beat me to it. 
Feynman is a big ass hero.
Literally the first link on google. It has a pretty decent educated-layman’s explanation.
The cliffnotes version is that stretching the rubber band places its molecules into a specific, ordered conformation. As a general rule (well, fundamental law of the universe really) putting things in more ordered states requires an input of energy. Rubber band molecules would rather not be ordered - like everything else they’d prefer to fly around randomly, so you need to put some work into it. Energy input into an object always results in some loss via heat.
I have seldom witnessed a more perfect answer to a SD question.
Nice job 74westy! (and nice job, Dr. Feynman, wherever you are)
I doubt if you’d get sufficient cooling from stretching rubber bands to get the cooling you want.
On the other hand, you can use this effect to build a nifty rubber-band motor
http://www.oberlin.edu/physics/catalog/demonstrations/thermo/rbmotor.html
There certainly are non-compressor based refrigerators based on thermodynamic principles. Peltier Coolers are used all the time.
I’m going to try it - I think it should be possible to do with fairly simple apparatus - a pair of metal pulleys turning at slightly different speeds, with a band stretched around them - the different speeds should mean that the band will be tighter on one side than the other, so it should arrive at one pulley warmer and arrive at the other cooler…