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Author Topic: If water molecules are very close together, then does shaking water induce heating through friction?  (Read 7884 times)

Sharif Massoud

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Sharif Massoud asked the Naked Scientists:

Hello Scientists,

I have a question regarding water' molecular makeup. I was told that due to the closeness of water molecules, it is very difficult to compress in liquid form. If that is true why doesn't the water heat up when vigorously shaken or agitated? Wouldn't the friction between the molecules create significant heat?

Thanks,
Sharif Massoud
United states
What do you think?


 

Offline lightarrow

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Sharif Massoud asked the Naked Scientists:

Hello Scientists,

I have a question regarding water' molecular makeup. I was told that due to the closeness of water molecules, it is very difficult to compress in liquid form. If that is true why doesn't the water heat up when vigorously shaken or agitated? Wouldn't the friction between the molecules create significant heat?

Thanks,
Sharif Massoud
United states
What do you think?
Friction of a liquid (especially against another liquid) is very low, it's for this reason car engines are lubricated with oil (for example). However a friction do really exist and the temperature increase is measurable with specific instruments.
 

Offline RD

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In 1843, Joule showed that heat was a form of energy and determined the physical constant now used as the S.I. unit for energy, the Joule (J). He demonstrated the mechanical equivalent of heat by measuring change in the temperature of water caused by the friction of a paddlewheel attached to a falling weight. This concept was further tested on his honeymoon in 1847 with his patient new bride Amelia Grimes, when Joule measured the temperature difference above and below the Sallanches waterfall in Switzerland!
http://www.bad.org.uk/public/historical_posters/JamesJoulePoster.pdf

 

Offline Make it Lady

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In 1843, Joule showed that heat was a form of energy and determined the physical constant now used as the S.I. unit for energy, the Joule (J). He demonstrated the mechanical equivalent of heat by measuring change in the temperature of water caused by the friction of a paddlewheel attached to a falling weight. This concept was further tested on his honeymoon in 1847 with his patient new bride Amelia Grimes, when Joule measured the temperature difference above and below the Sallanches waterfall in Switzerland!
http://www.bad.org.uk/public/historical_posters/JamesJoulePoster.pdf


Great link. I just love thinking about these fab scientists doing wacky things (but on your honeymoon!!!)
 

Offline RD

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If you think Joule was all-work-and-no-play then check out Einstein's "contract" with his wife ...
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Einstein became estranged from his wife. The biography reprints a chilling letter from Einstein to his wife, a proposed "contract" in which they could continue to live together under certain conditions. Indeed that was the heading: "Conditions."

A. You will make sure
1. that my clothes and laundry are kept in good order;
2. that I will receive my three meals regularly in my room;
3. that my bedroom and study are kept neat, and especially that my desk is left for my use only.
B. You will renounce all personal relations with me insofar as they are not completely necessary for social reasons…

There’s more, including "you will stop talking to me if I request it." She accepted the conditions. He later wrote to her again to make sure she grasped that this was going to be all-business in the future, and that the "personal aspects must be reduced to a tiny remnant." And he vowed, "In return, I assure you of proper comportment on my part, such as I would exercise to any woman as a stranger."
http://www.neatorama.com/2007/03/26/10-strange-facts-about-einstein/

 

lyner

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Mechanical energy to heat energy - bad value. It takes 4200J to raise the temperature of 1kg of water by 10C. That's the equivalent of lifting that 1kg 420m. SO, a whole lot of shakin goin on to warm it up a bit.
Mr Joule needed a very sensitive thermometer - as well as an understanding wife.
 

Offline Bored chemist

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I think there's a missing factor of about 9.8 in that calculation.
 

lyner

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I used the 'GCSE g factor' of 10; near enough for Jazz (certainly near enough to measure).
 

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