I know that it takes 1 BTU to raise 1 gallon of water 1 degree Fahrenheit. Question: How many BTUs does in take to lower 1 gallon of water 1 degree Fahrenheit? Is it the same in reverse? Meaning 1 BTU.
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Replies
That is 1 BTU to raise 1 POUND of water by 1 degree Fahrenheit. A gallon is about 8.33 lb. Heat added or removed is the same, and it's all additive. Add 10 BTUs today, 5 more tomorrow, remove 15 the next day, and the temperature is right back where you started.
If you are from the rest of the world, it's 1 kilocalorie to change 1 kilogram of water by 1 degree Centigrade.
This property of water is called its "heat capacity." Water, at just about 1.0 (either set of units), is rather high as far as materials go. Hydrocarbons are more like 0.4 or so, and air is around 0.25.
Ah, does this give you what you wanted, or are you wishing I'd stopped after the first sentence?
This property of water is called its "heat capacity."
Actually, it's called its "specific heat" which is the amount of heat required to raise a unit mass of material one degree.
The "heat capacity" of an object is the amount of heat required to raise the entire volume of the object one degree.
So, while the specific heat of water is one (BTU/lb*°F), the heat capacity of 1 gallon of water would be 8.34 BTUs.
Riversong HouseWright
Design * * Build * * Renovate * * ConsultSolar & Super-Insulated Healthy Homes
Depending on where the term is used and how it is expressed, the term "heat capacity" may be synonymous with specific heat. In my line of work, heat capacity of fluids usually is expressed as BTU/lb-F or kcal/kg-C.Someone in a field where the energy-carrying capacity of a thermal mass is of interest (large water tank, concrete wall, etc), may well be referring to heat capacity of the particular massive item (ie BTU/F or kcal/C).
Here's another one for all you whiz kids that remember your thermodynamics.
Is the energy change required to freeze water the same as that required to melt ice?
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"A stripe is just as real as a goddamn flower."
Gene Davis 1920-1985
yup, as long as you control the atmospheric pressure. meaning, one can't be in florida and the other in the rockies. as you know, the one in the rockies will require a lot more energy, unless you increase the pressure to offset the altitude (lower pressure).
Let's consider this as everything being done in same room.
Caloric input to thaw as compared to caloric outtake to freeze.
Equal?
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"A stripe is just as real as a goddamn flower."
Gene Davis 1920-1985
pretty much, but remember water can go from a frozen state to a sublimation state without a liquid phase. kind of silly for what you are asking. here is my point, always take into consideration the surrounding water content of the air, the relative humidity or percent of water vapor in the air will make a difference in how much energy it takes to move and transfer the liquid to a different physical state. all this means is that it takes less energy to evaporate water in arizona than it would in southern florida. look at it this way, if you are sweating and the air is dry you will evaporate and cool the skin faster than if the air is saturated.
this is all theoretical, but fairly accurate. where you looking for some specific numbers? this probably isn't of much help to you, sorry.
Enthalpy, or heat content (relative to some reference condition), is a "state function," meaning that the enthalpy is a function of the state of the material (temperature, pressure, phase). It is independent of the path taken to bring it to those conditions.So, if you change the phase of the water from water at 32 F to ice at 32 F, you have reduced its enthalpy by the heat of fusion (about 143 BTU/lb). If you thaw it back to liquid at 32 F, you've added that amount of heat back in.OK, here's another one for you:You have an uninsulated glass vessel, partly filled with water, and the only outlet at the top is connected to a good vacuum pump. You turn on the pump and draw down the pressure. What happens inside? As time goes further on, what other things do you observe?
You have an uninsulated glass vessel, partly filled with water, and the only outlet at the top is connected to a good vacuum pump. You turn on the pump and draw down the pressure. What happens inside? As time goes further on, what other things do you observe?
Dick, funny that you asked this question...I learned this just last night.
first the water will boil and then freeze..amazing!
http://www.youtube.com/watch?v=DhR6EjBCQJw
lots of other good Julius Sumner Miller videos at YouTube
Yes. It's called the heat of fusion. It's the difference between the enthalpy of the solid state and liquid state at 32F. What is interesting (to some people, anyway) is that you actually have to drop slightly below the freezing temperature to get an ice crystal to start growing. Not true for melting, which in Lake Placid, occurs in summer.
Here's another paradox:
Why does hot water freeze faster than cold water? (hint: it really does)
We did this one last year. Still not sure if I'm a believer.83651.20
If you were given the correct explanation, you'd be a believer since it makes perfect sense.
I don't know why but I know Zamboni drivers have known this since they first made Zambonis.
They can't get your Goat if you don't tell them where it is hidden.
Zamboni drivers have known this since they first made Zambonis
So did Aristotle, Francis Bacon & Descartes. But to this day no one but me knows why.
Ok I will bite. I went to several web sites for the answer and from what I read there are still a number of variables that can contribute to this . But I did not see a single source that had only one reason , and a definitive one at that . So Please share .
They can't get your Goat if you don't tell them where it is hidden.
clue #2: 101111.15
clue #3:
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I am sorry but I cannot understand your clue. Please either speak plain English for the undereducated or don't bother trying to explain it to me . Others here may enjoy and be able to learn from that form of education, I do neither. Thanks.
They can't get your Goat if you don't tell them where it is hidden.
Because of the strong hydrogen bonding in water molecules, liquid water exists in three somewhat distinct "phases".
At high temperatures, when there's enough kinetic energy to overcome the hydrogen bonds between molecules, the water molecules are seperate.
At somewhat cooler temperatures, the molecules begin to clump. And as water cools further, the clumps begin to cluster.
Two things are necessary for water to freeze. It must cool to 32° and the molecules must arrange themselves in an hexagonal crystalline structure.
Cold, clustered water molecules can easily drop below freezing temperature, but have a real hard time rearranging themselves into a crystalline form.
Clumped molecules can rearrange themselves a little faster.
But the individual molecules, if they lose heat quickly, will form crystals almost instantly once they drop below 32°.
[I'm not really the only one who knows this. I think I read about it 30 years ago in Scientific American.]
Thank you. That I can understand. Sometimes I forget that an apprentice has to know what a framing square is before I ask him to use it. Being educated and knowledgeable has it's responsibilities.
They can't get your Goat if you don't tell them where it is hidden.
Doctor Riversong,
That was excellent! where did you find the illustration?
John B
That was excellent! where did you find the illustration?
I just Googled "clusters of water molecules" to get something approximating what I was trying to illustrate.
That pic was stolen from the Argonne National Lab.
I've been thinking that this pardoxical quality of water may very likely be a quantum effect, since it's been experimentally demonstrated that conscious intention can alter the hydrogen bonding of water molecules.
Dr. Emoto's work with conscious intention and ice crystals is worthy of note:
Dr. Masaru Emoto was born in Japan and is a graduate of the Yokohama Municipal University and the Open International University as a Doctor of Alternative Medicine. His photographs were first featured in his self-published books Messages from Water 1 and 2. The Hidden Messages in Water was first published in Japan, with over 400,000 copies sold internationally.
You Make Me Sick
What has put Dr. Emoto at the forefront of the study of water is his proof that thoughts and feelings affect physical reality. By producing different focused intentions through written and spoken words and music and literally presenting it to the same water samples, the water appears to "change its expression".
View Image Love and Gratitude
Essentially, Dr. Emoto captured water's 'expressions.' He developed a technique using a very powerful microscope in a very cold room along with high-speed photography, to photograph newly formed crystals of frozen water samples. Not all water samples crystallize however. Water samples from extremely polluted rivers directly seem to express the 'state' the water is in. Dr. Masaru Emoto discovered that crystals formed in frozen water reveal changes when specific, concentrated thoughts are directed toward them. He found that water from clear springs and water that has been exposed to loving words shows brilliant, complex, and colorful snowflake patterns. In contrast, polluted water, or water exposed to negative thoughts, forms incomplete, asymmetrical patterns with dull colors.The implications of this research create a new awareness of how we can positively impact the earth and our personal health. The success of his books outside Japan has been remarkable. Dr. Emoto has been called to lecture around the world as a result and has conducted live experiments both in Japan and Europe as well as in the US to show how indeed our thoughts, attitudes, and emotions as humans deeply impact the environment.
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Mozart Symphony
View Image Heavy Metal Music
Edited 2/21/2008 12:51 pm ET by Riversong
Try this, You are being asked to teach Thermodynamics to a class of 2nd graders. Can you do that ?
They can't get your Goat if you don't tell them where it is hidden.
Why does hot water freeze faster than cold water? (hint: it really does)
Define the parameters of what is considered "hot" & what is "cold".
“The world is a dangerous place, not because of those who do evil, but because of those who look on and do nothing.” —Albert Einstein
no..it's less
melting requires additonal heat
edit:
ok..it looks like we have three different answers
oh , mighty inquisitor...
pray tell the school solution
from ice to water.. we have to add heat of hydration
from water to ice we have to add the heat of fusion
i don't know if those are equal
Mike Smith Rhode Island : Design / Build / Repair / Restore
Edited 2/20/2008 9:04 pm ET by MikeSmith
Edited 2/20/2008 9:05 pm ET by MikeSmith
Sorry, Mike, I can't remember either. It all has to do with either entropy or enthalpy. Or maybe not.
Wednesday's are bad for me, as it is German beer and brat and kraut night at a couple hot spots in town. Too many St Pauli Girls, for me to discuss thermo.
Besides, the only meltdown I am interested in right now is that of Mizz Rodham Clinton. Watching her descent into the maelstrom is, for me at least, even better than seeing the Giants beat the Patriots. And the last quarter of this game is going to go on for at least the next month.
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"A stripe is just as real as a goddamn flower."
Gene Davis 1920-1985
just so you'll feel better... you and your wife can cancel our hillery votesMike Smith Rhode Island : Design / Build / Repair / Restore
We could not, Mike. New York had a closed primary.
How many delegates might she net out of R.I.?
As I said in another post, she might come out of this looking so bad that Al Sharpton can run and beat her out of her Senate seat, in the next congressional election when her term's up.
But if that happens, maybe she and Bubba will move up to Newport and do it all over again.
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"A stripe is just as real as a goddamn flower."
Gene Davis 1920-1985
RI is set up for independents now...
as long as i disaffiliate after leaving the booth, i can vote in either primary
<<<<
How many delegates might she net out of R.I.?>>>>
hard tellin...not knowinMike Smith Rhode Island : Design / Build / Repair / Restore
heat of hydration
Trying to stir the pot with inclusion of totally different process??
Heat of hydration has absolutely nothing to do with melting or freezing.
PS, re: per a later post in the thread - always did wonder how people could misinterpret stuff so much the'd vote for Hillary <G>
Edited 2/21/2008 5:08 am ET by junkhound
you mean we're not talking about concrete ?
well.....SPEAK UP NEXT TIME !Mike Smith Rhode Island : Design / Build / Repair / Restore
In every source I've seen, the two terms are distinct. For instance:
http://en.wikipedia.org/wiki/Heat_capacity#Heat_capacity
Specific heat capacity, also known simply as specific heat, is the measure of the heat energy required to increase the temperature of a unit quantity of a substance by a certain temperature interval. The symbols for specific heat capacity are either C or c depending on how the quantity of a substance is measured (When mass is the unit quantity, the symbol for specific heat capacity is lowercase c. When the mole is the unit quantity, the symbol is uppercase C). In the measurement of physical properties, the term “specific” means the measure is a bulk property (an intensive property), wherein the quantity of substance must be specified.
Heat capacity (symbol: Cp)—as distinct from specific heat capacity—is the measure of the heat energy required to increase the temperature of an object by a certain temperature interval. Heat capacity is an extensive property because its value is proportional to the amount of material in the object
Riversong HouseWright
Design * * Build * * Renovate * * ConsultSolar & Super-Insulated Healthy Homes
IBI,
To raise the temperature of a liquid, you need to add heat to the liquid. To lower the temperature of a liquid, you need to remove heat from the liquid, not add it. If you successfully lower the temperature of a liquid, you will produce heat.
"If you successfully lower the temperature of a liquid, you will produce heat."
Well, you will release stored heat.
Not coincidentally, ignoring inefficiencies in the system, you'll release the exact same amount of heat it took to get the water to the higher temp in the first place.
Mike HennessyPittsburgh, PA
"Well, you will release stored heat."Well, it won't be "released" either. It is simply allowed to move to something colder, and that something else then "has" that much more heat and gets correspondingly warmer.Jeepers, we can have all sorts of fun on this one, trying in vain to "out-terminology" each other!
"It is simply allowed to move to something colder"
Like my chilly part of the world? Please?
;-)
Mike (Ready for Spring) HennessyPittsburgh, PA