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Author Topic: Does Water Heat Up And Cool Down At The Same Rate ?  (Read 1900 times)

Offline neilep

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Dearest Water-Temperaturologists,

As a s sheepy I of course luff water. Water is my all time favourite liquid to imbibe. Well done to the person who invented water who we all know was Hyacinth the 2nd of Oxbridgeshire in 1876**

Take a look at these two giant glasses of water !...For scale reasons I'm five feet tall !!


Two really big glasses of water just moments ago !

If I was to pour boiling water in one and room temperature water in the other is there an experiment i could do determine whether water cools and heats at the same rate ?

Does Water Heat Up And Cool Down At The Same Rate ?

I of course don't know how to go about doing such an experiment, (I'm a sheep innit?)

If ewe can answer this for me then I can enjoy a dialogue with the bloke next to me next time I go to a public urinal !..I'm sure the chap next to me would enjoy such a rapport !!

whajafink ?

Hugs and shmishes


mwah mwah mwah

Neil

** This is true because someone told me it !


 

Offline Colin2B

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Re: Does Water Heat Up And Cool Down At The Same Rate ?
« Reply #1 on: 31/07/2015 23:02:31 »
Not if you do it the way you describe. What would make the water at room temp change?
How about a rough experiment, relative to room temp, one glass water +10 The other -10. Which one reaches room temp 1st. Remember to cover both glasses.
 

Offline alancalverd

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Re: Does Water Heat Up And Cool Down At The Same Rate ?
« Reply #2 on: 01/08/2015 00:08:11 »
Newton's Law of Cooling, which apparently predates the discovery of water by about 200 years, applies to homogeneous bodies in forced convection but is good enough to describe your experiment for the first few minutes.

"The rate of change of temperature is proportional to the temperature difference between the body and the ambient air."

So if the ambient was 20 deg C, the initial rate of cooling from 100 deg C would be 80 times the rate of cooling from 21 deg C, assuming identical glasses, well stirred, etc.

Rates of heating are, in practice, rather less predictable as the transfer efficiency depends on the microturbulence around the glass but in true forced convection, where the air flow is very rapid compared with natural convection, the coefficients should be the same. 
 

Online PmbPhy

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Re: Does Water Heat Up And Cool Down At The Same Rate ?
« Reply #3 on: 01/08/2015 04:53:48 »
I would suggest placing the two glasses in thermal contact. In that case they'd have to change temperature at the same rate, wouldn't they? After all the rate at which heat flows out of the hot water is the same rate at which heat flows into the cold water.
 

Offline alancalverd

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Re: Does Water Heat Up And Cool Down At The Same Rate ?
« Reply #4 on: 01/08/2015 09:48:24 »
Only if they are at equal and opposite temperature intervals compared with the ambient.
 

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Re: Does Water Heat Up And Cool Down At The Same Rate ?
« Reply #4 on: 01/08/2015 09:48:24 »

 

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