# If temperature is motion, why doesn't stirring water make it boil?

• Bradley in SD
In summary, the two students have different ideas about how to heat a room with wind power. One student thinks of a windmill with an electric motor that is connected to resistance heating in the room. The other thinks of a windmill with a shaft that is connected to blades that rotate. Bevel gears are probably more efficient than a cable, and orientation is simply a matter of putting a 'tail' on the nacelle.
Bradley in SD
If the temperature of a fluid is a result of the molecules bumping into one another, why doesn't stirring or shaking a glass of water make it boil? Or at least raise its temperature?

Thanks for any help with this!

How do you know it doesn't? That's a Joule of a question!

If you ( TVP; I'm ignoring you) shake or stir a container of liquid vigorously enough, it will boil as a result of internal friction raising the temperature. I don't believe that it's humanly possible to do so, but a machine might be able to pull it off.

when i was an undergrad at the U of North Dakota (the 1970s), one of my high school classmates chose engineering at our arch-rival, North Dakota State. anyway i visited him once at his school (NDSU) where he showed me a project he was working on (he was ME, even though i am EE) about heating with wind power. here is how two different engineering (students) think: i thought "windmill shaft connected to generator with electric cables connected to resistance heating in the living space." these MEs were thinking: "windmill shaft connected to tough-a ss lubricated mechanical cable that goes into living space where it churns up some big vat of water." they had a 1/10th-size prototype where they could drive the shaft with an electric motor for demonstration/testing purposes. i was surprized how quickly the water in that 10 gallon tank heated up.

Who'd a thunk...? Interesting.
I wonder how much extra heat was lost to internal friction of the cable. A bare driveshaft probably would have been even more efficient.

The guy that invented most of thermodynamics had a job drilling the big hole down the middle of brass cannons - which was done in a bath of water to keep them cool.

rbj said:
when i was an undergrad at the U of North Dakota (the 1970s), one of my high school classmates chose engineering at our arch-rival, North Dakota State. anyway i visited him once at his school (NDSU) where he showed me a project he was working on (he was ME, even though i am EE) about heating with wind power. here is how two different engineering (students) think: i thought "windmill shaft connected to generator with electric cables connected to resistance heating in the living space." these MEs were thinking: "windmill shaft connected to tough-a ss lubricated mechanical cable that goes into living space where it churns up some big vat of water." they had a 1/10th-size prototype where they could drive the shaft with an electric motor for demonstration/testing purposes. i was surprized how quickly the water in that 10 gallon tank heated up.

That's how they heat the hot tub at Slippery Art's Saloon in Dodge. They put the barman, Lars, on a treadmill and put a picture of the Lennon sisters on the other end.

Takes a while, but what the heck else can you do when it's -28 outside?

Danger said:
Who'd a thunk...? Interesting.
I wonder how much extra heat was lost to internal friction of the cable. A bare driveshaft probably would have been even more efficient.

in fact, that was another design they were working on with a shaft. but how do you connect the driveshaft going up the middle of the windmill tower, to these blades? with a 90o bend, that can't be too awful efficient. also, how do you keep the windmill pointing toward the wind when there is constantly this torque on the windmill platform that wants to turn it? i don't know the answers, it's what came to my mind then as it intrigues me now.

BTW, Bradley, ND beets SD anyday!

Bradley in SD said:
If the temperature of a fluid is a result of the molecules bumping into one another, why doesn't stirring or shaking a glass of water make it boil? Or at least raise its temperature?

Thanks for any help with this!

This is exactly what Joule did some 150 years ago. He did not make it boil but he DID measure a rise in the temperature (and the reason he could do that was that he was a brewer, meaning he had access to good thermometers).

wiki
http://en.wikipedia.org/wiki/James_Joule

rbj said:
in how do you connect the driveshaft going up the middle of the windmill tower, to these blades?
... also, how do you keep the windmill pointing toward the wind when there is constantly this torque on the windmill platform that wants to turn it:

Bevel gears are probably more efficient than a cable. Hypoids would keep it fairly quiet, as well. Orientation is simply a matter of putting a 'tail' on the nacelle.
What the hell do beets have to do with this? They're one of the most disgusting vegetables on the face of the planet.

Danger said:
If you ( TVP; I'm ignoring you) shake or stir a container of liquid vigorously enough, it will boil as a result of internal friction raising the temperature. I don't believe that it's humanly possible to do so, but a machine might be able to pull it off.
Might? We did a chilled water plant for a cocoa processing company. They use 160kW motors in their grinders (think: giant blender, with knives that could...well...think: "Charlie and the Chocolate Factory" meets "Saw"...) -- where do you think all that energy goes? The cocoa goes into the grinder at 100-110F and leaves at 140-160F. The cocoa acutally acts as a coolant for the grinder. The rest of the heat is absorbed by jacket water or dissipated into the room (they keep it at 110F year-round to keep the cocoa liquid). When they were commissioning the plant, they had a flow problem and the cocoa in one of the grinders actually caught fire.

http://www.wiener.nl/CocoaLiquor/Index.asp

Last edited by a moderator:
Quick answer... It does. Even if you stick your finger into a glass of water that is perfectly matched to your body temperature and stir it, the water is hotter. If you want to boil it, just stir faster...lol. BTW, stirring a cup of coffee with your finger will work, but is incredibly inefficient, not to mention painfull.

Speaking of accelerating liquids causing rises in temperatures, if you have connect the input to the output of a high head pump you can heat up the water and destroy the pump rather quickly.

Danger said:
Orientation is simply a matter of putting a 'tail' on the nacelle.

well, something is twisting the vertical drive shaft, and because it is doing work, there has to be a resisting torque to that twist. two every (rotational) action there is an equal and opposite reaction. what would otherwise be a freely rotating platform (that would, if there were no other torques, orient the windmill to point to the wind) now has a shaft trying to turn it. it needs to have an opposite torque and the tail wouldn't be enough.

i think it needs two vertical shafts turning in opposite senses to cancel the torrques allowing for the wind and the tail to orient the windmill.

Danger said:
Bevel gears are probably more efficient than a cable. Hypoids would keep it fairly quiet, as well. Orientation is simply a matter of putting a 'tail' on the nacelle.
What the hell do beets have to do with this? They're one of the most disgusting vegetables on the face of the planet.

Put a little sugar on them. Helps the vegetable go down.

## 1. Why doesn't stirring water make it boil?

Stirring water does not make it boil because heat, not motion, is the main factor in causing water to boil. While stirring may increase the motion of water molecules, it does not significantly increase the temperature.

## 2. Is temperature really just motion?

Yes, temperature is a measure of the average kinetic energy, or motion, of molecules in a substance. The higher the temperature, the faster the molecules are moving.

## 3. Can stirring water make it boil faster?

No, stirring water will not make it boil faster. Boiling occurs when the temperature of the water reaches its boiling point, which is 100 degrees Celsius at sea level. Stirring does not significantly increase the temperature of the water.

## 4. Why does water boil at a specific temperature?

Water boils at a specific temperature because it is the point at which the vapor pressure of the liquid is equal to the atmospheric pressure. At this point, the molecules have enough energy to break free from the liquid and become a gas.

## 5. Can other factors besides heat affect the boiling of water?

Yes, factors such as altitude, atmospheric pressure, and the presence of impurities can also affect the boiling point of water. For example, at higher altitudes, where atmospheric pressure is lower, water will boil at a lower temperature.

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