WATER ? please help explain this

reply to post by jlafleur02


Perhaps the water is not expanding. Perhaps it's decompressing. To compress water you add heat. You have to put energy in to compress it. When you release the heat, it decompresses. Not really, but we're just looking at the situation from the other way around.

It's not free energy because yes it produces a lot of force when it decompresses, but to make the water do it again, you have to add energy back into the system. You have to add heat back into the system to compress it again. So that's where you take your energy loss and what prevents it from being free. Once you've lost the heat, you gotta go get it again.

I'm no expert in anything.

The answer to the OPs question was answered on the first page, I believe.

Someone mentioned thermal energy ...what effects the water to freeze is starting the chain reaction, leading to the pipes bursting under the right circumstances.

Chemical reactions are induced not only by mixing and blending and stirring, but also adding heat, or in some cases- nitrogen or stuff that changes the thermal temperature of respective element(s).

As this element being water, the basic fundamentals remain should I say, constant?

Did I mention I'm no expert?

Originally posted by tinfoilman
reply to post by jlafleur02

 

Perhaps the water is not expanding. Perhaps it's decompressing. To compress water you add heat. You have to put energy in to compress it. When you release the heat, it decompresses. Not really, but we're just looking at the situation from the other way around.

It's not free energy because yes it produces a lot of force when it decompresses, but to make the water do it again, you have to add energy back into the system. You have to add heat back into the system to compress it again. So that's where you take your energy loss and what prevents it from being free. Once you've lost the heat, you gotta go get it again.

edit on 31-12-2010 by tinfoilman because: (no reason given)

edit on 31-12-2010 by tinfoilman because: (no reason given)

No, you have it backwards.Water contracts (not compresses) as you take the heat out, at least down to about 4 degrees C. Then, if you take more heat out, it expands some, until it freezes, upon which it expands about 9%. So you take heat energy out of it to at first contract it, then expand it. The extreme difficulty in compressing water, or in resisting its thermalexpansion is a function of its bulk modulus of 2.2 Gigapascals per kilogram.

The answer to why is in one of the earlier posters links, the molecular structure of the water is what causes the expansion before freezing.

While it may seem like it, this breaks no laws of physics simply because water has plenty of energy in it to perfom work, such as bursting a pipe. liquid water at 25C has roughly 286KJ of energy per mole of water. According to waters enthalpy of formation. The energy is hanging out in a few places but mostly in the lattice I believe.

This energy is usually released as heat during changes in temp but in the case of a pipe the pressure is not constant which causes the heat to become work.

During water's fusion from a liquid to solid state some of this energy is used and stored to form the solid crystal lattice. In the case of a bursting pipe this energy is greater than what is needed to overcome said pipe.

So by simply looking a periodic table, hydrogens atomic mass is 1 (x2 for h20) and oxygen is 16. so for every 18 grams water at 25C they contain 286KJ of energy.

In a 5 gallon bucket you have roughly 18,900 grams. which is 1050 moles of H20. (18,900 / 18 )

So only 5 gallons of water at room temperature holds 300,300KJ of energy.

The enthalpy fusion of water is 6 KJ per mole, so 5 gallons of water crystallizing to ice uses 6300KJ of its energy which is 4646641.54059 pounds of force per foot.

Thats more than enough to bust a few pipes. =P

(Disclaimer : I'm mearly a student, not an expert. This is only my take on it and if somethings off I apologize.)

reply to post by cycondra


So you can freeze water then burst a pipe about 45 times before the water runs out of energy?

reply to post by jlafleur02


Well due to constant transfer of energy between atoms anywhere and everywhere.. no It's potential energy in the calculations.

Still no explanation for this. If its due to the transfer of energy from molecule to molecule this should be measurable.

As for the explanation that its the crystalline structure of the molecule, this still doesn't show where the energy comes from. The math doesn't add up

reply to post by jlafleur02


Energy = heat

there will always be heat unless the temp is absolute zero, it has been explained.

It's not a closed system when you have external factors such as weather. Problem solved and all questions answered...

Originally posted by jlafleur02
I have a question about freezing water. In a water line, when the water freezes The pipe will burst. There isn't energy being put into the water it is actually being taken out of the "system". It produces a great force to burst the pipe. To me this defies the Laws of conservation of energy.

The law of conservation of energy is an empirical law of physics. It states that the total amount of energy in an isolated system remains constant over time (is said to be conserved over time). A consequence of this law is that energy can neither be created nor destroyed: it can only be transformed from one state to another. The only thing that can happen to energy in a closed system is that it can change form: for instance chemical energy can become kinetic energy.

This is from wikipedia

When a force is create it is a form of energy. If I took a box that can expand, filled it with water, then hooked up an assembly of some kind to use this force to create energy the water should experience a loss of mass or should show some temperature change.

I have several questions:
1. Does it take energy to remove heat from water? I know there are freezers and such, but I mean in nature does it take energy to freeze a pond?
2. how much force is need to burst these pipes and can It be accounted for as to where the energy to do this comes from.
3. I know that water expands due to its molecular structure when it freezes. How can it expand when its physical state is being lowered. As ice it is a certain volume then it goes to water, the volume shrinks then to a gas the volume expands? also is there another compound that does this.

In order to apply that quote from Wikipedia, you have to define what is included in the "closed system". A water pipe isn't really a closed system, it's exchanging heat with the surrounding environment. So we can't apply a law relating to a closed system to something that's not a closed system.

But let me see if I can answer your questions without having to get into that.

The answer to question 1 is best (to me) described by this diagram:

Phase changes

[atsimg]http://files.abovetopsecret.com/images/member/c6083ff0fc68.gif[/atsimg]

Note I will refer to temperatures in degrees C.

Take a 1000 gram block of ice at a temperature of -40 degrees C, apply heat to it, and it warms up, to -30, to -20, to -10, and then 0C. By the time the ice initially gets to 0 degrees C, we have added 20,000 calories of heat energy (40 degrees x 0.5 specific heat in cal/g-deg C x 1000 g), and then an interesting thing happens. Even though we are still applying heat to it, it doesn't continue to get warmer like we might expect. The temperature gets "stuck" at 0C which is what the horizontal line near the left of that diagram labeled "melting ice" represents. This interesting phenomena is called "heat of fusion" not to be misconstrued with any type of nuclear fusion. It takes a relatively large amount of energy to turn the ice into water, about 80 calories per gram. This means we have to add 80 cal/g x 1000 g = 80,000 calories of heat energy. the amount of energy required to go from 0 degree ice to 0 degree water.

This "heat of fusion" I think is the key to answering your question. The 80,000 calories of heat energy doesn't increase the water temperature at all, it's energy that's being stored in the water to make it a liquid phase instead of a solid phase, by breaking the chemical bonds of the ice. Once the 80,000 calories is added and all the ice is melted, if you apply another 100,000 calories of heat, the water will increase in temperature from 0 degrees to 100 degrees C. Then the temperature gets "stuck" again for the next phase change to steam, where we must apply 539,000 calories of heat to go from 100 degree water to 100 degree steam.

So that's the answer to your question 1 in reverse, it shows how much energy must be added to the water to heat it from ice to a liquid to a gas (at normal atmospheric pressure, at sea level). That's going from left to right in the diagram. So to answer question 1, just do the reverse, take exactly that number of calories out of the water and you lower the energy and change the phases in the reverse direction (go from right to left in the diagram). Does this make sense? Are you with me so far?

Your second question "how much force is need to burst these pipes and can It be accounted for as to where the energy to do this comes from" was partly answered here:

www.abovetopsecret.com...

Originally posted by 4nsicphd
When water freezes, it expands about 9%. So you're trying to squeeze 109 whatevers of water into 100 whatevers. The bulk modulus of water is 2.2 GPa So, to compress the water that much requires a pressure of .09*2.2, or about 2 GPa, which translates to a little over 290,000 psi. That's why your pipes burst. A regular PVC water pipe (3/ inch) is supposed to be good to about 1500 psi. High pressure is rated to 2200 psi. Copper is only good to about 800 psi.

That tells you how much pressure is needed to burst the pipes, 800 PSI rating for copper and it would need to have a rating of perhaps 300,000 psi to not burst. Where does the energy come from?

Remember above when we added 80,000 calories to the 0 degree ice to convert it to 0 degree water? That's where the energy comes from, and the force is generated by converting that latent heat of fusion energy into molecular bond energy exactly as described in this post (which also answers question 3):

www.abovetopsecret.com...

Originally posted by 4nsicphd
Each molecule can form a hydrogen bond with 4 other molecules in a tetrahedral form. Now these attractive forces are not really strong, but there are really a lot of them - roughly 15,000,000,000,000,000,000,000,000 molecules in each pint. Think about what that many forces, even though small, can do.

That's essentially the answer, although there are 16 different types of ice and I thought the Wiki was correct that the hexagonal crystalline form is the most common type:

Ice may be any one of the 15 known crystalline phases of water.

-ice Ih: Normal hexagonal crystalline ice. Virtually all ice in the biosphere is ice Ih, with the exception only of a small amount of ice Ic.
-ice lc: A metastable cubic crystalline variant of ice. The oxygen atoms are arranged in a diamond structure. It is produced at temperatures between 130 and 220 K, and can exist up to 240 K,[40][41] when it transforms into ice Ih. It may occasionally be present in the upper atmosphere....
-ice III: A tetragonal crystalline ice, formed by cooling water down to 250 K at 300 MPa. Least dense of the high-pressure phases. Denser than water.....

So 4nsicphd is right about the fact there's a tetragonal type of ice, but it's a high pressure phase of ice and it won't burst your pipes because it's less dense than water.

When you apply that 80,000 calories to the water it's sort of like pumping water up to a water tower, it becomes stored energy. When you allow the water from the water tower to fall back to ground level, it can do work like power a water wheel, or hydroelectric dam. When you allow 4 degrees liquid water to turn to -1 degrees ice, likewise it's capable of doing work by releasing the 80,000 calories of stored energy which was previously added in the heat of fusion phase change from ice to water. The work is actually done by the millions of molecular bonds forming as the water freezes as 4nsicphd describes.

Regarding question 3, you almost answer your own question: "I know that water expands due to its molecular structure when it freezes. How can it expand when its physical state is being lowered. As ice it is a certain volume then it goes to water, the volume shrinks then to a gas the volume expands? also is there another compound that does this."

Liquids and gases don't have crystals, so the molecular spacing is determined by phase, temperature, pressure etc. When materials turn from liquid into solid materials, some materials like water, form crystals. The ice crystals happens to take up more space than the liquid form, because of the crystalline structure of water ice crystals which 4nsicphd described pretty well, it has to do with the shape of the water crystals and the spacing that results between the molecules in the crystal lattice.

Other compounds that expand on freezing are: silicon, gallium, germanium, antimony, bismuth, plutonium and other compounds that form spacious crystal lattices with tetrahedral coordination

reply to post by Arbitrageur

When you apply that 80,000 calories to the water it's sort of like pumping water up to a water tower, it becomes stored energy. When you allow the water from the water tower to fall back to ground level, it can do work like power a water wheel, or hydroelectric dam. When you allow 4 degrees liquid water to turn to -1 degrees ice, likewise it's capable of doing work by releasing the 80,000 calories of stored energy which was previously added in the heat of fusion phase change from ice to water. The work is actually done by the millions of molecular bonds forming as the water freezes as 4nsicphd describes.

So how does the water that releases energy, which should be measurable, convert it to a force. I mean if you put 80,000 calories into it to get it to a certain state then take out the 80,000 calories and it returns to the original state. My best understanding of this would be that the "natural state of water would be ice. By adding enough energy you would disrupt this state. So when we take away the energy it goes back to its normal state which is ice. The confusing part is during this normal state, ice , there is a constant attraction that forms the crystalline structure.
So by removing the stimulus of energy and the ice returns to its normal state we recreate the bonds and these bonds can exert a great amount of force. where does the energy come from that allows these bonds to reform. we are talking about taking energy out to lower the water to ice and as we do it a force is created that is independant of the release of 80,000 calories that must be released to do this.

reply to post by jlafleur02


Thinking about this one idea I had was that the desire for the molecules to form that bond is always there. the removal of heat will slow them down enough to allow the creation of that bond. the point still remains that the bonds are formed during this phase and a mechanical energy is still exerted.
The energy stored in the water phase must be the force that is keeping these molecules from joining and forming ice. If this is the case does water need a heat source to remain at the water state? I mean to keep the water in the liquid form does energy constantly have to be added to it to maintain that liquid state or if you had a volome of water that was in a vacumm and around that water no heat transfer occured ( in theory) would it turn to ice eventually? If the energy in the water is doing work to keep the water molecules from joining would we have to add more energy to the water to maintain this state or would the enrgy present be enough.

Water is somewhat unique as a compound in that it reduces density when it turns to a solid (ice) and yep, that can do serious damage if it's trapped in a pipe or container. It's also very convenient that it doesn't become more dense when it freezes (and sinks) because the oceans would be pretty much all ice with a very thin liquid layer on top in the tropics otherwise.

Anyone know of other compounds that lose density on solidifying?

Originally posted by jlafleur02
we are talking about taking energy out to lower the water to ice and as we do it a force is created that is independant of the release of 80,000 calories that must be released to do this.

It's not independent. It's a different form of energy, but it's related.

Push a ball up an incline. You have added potential energy with the work you've done.

Now release the ball, it rolls down the hill. The movement is a form of kinetic energy.

You can say the kinetic energy is a different form of energy, but energy is conserved, it just changes from one form (potential) to another (kinetic). So the ball rolling at the bottom of the hill and the ball sitting still at the top of the hill are not independent, they are dependent and very related.

The same thing happens when you heat up and cool down water. When you heat it up so it's liquid, it has what's called "latent" energy which is analagous to the "potential" energy of the ball you pushed up a hill. And when that latent energy is released, it's converted from one form of energy to another form of energy, just like the ball's potential energy being converted to kinetic energy.

Frequently the way water releases the stored energy is by imparting kinetic energy to the surrounding environment. So the liquid water has energy to give back, it can lose this energy by heating the surrounding air molecules if they are colder and by using part of the stored or latent energy to reform the molecular bonds of ice as it does so, possibly breaking pipes in the process.

So I think that's your misunderstanding, you think it's independent, it's not. When you melted the kg of ice with a torch, and turned it to water, you gave it all the energy it needed to burst pipes when you did that. The energy is stored in the water as long as it's liquid. When it turns back to a solid, it releases that energy, heating the surrounding air, or bursting pipes, etc. So the source of the energy was the torch you melted the ice with, in that example.

Originally posted by Pilgrum
Anyone know of other compounds that lose density on solidifying?

I just answered that at the end of my post a few posts before you asked.

It was part of the third question in the OP.

Originally posted by jlafleur02
The energy stored in the water phase must be the force that is keeping these molecules from joining and forming ice. If this is the case does water need a heat source to remain at the water state? I mean to keep the water in the liquid form does energy constantly have to be added to it to maintain that liquid state or if you had a volome of water that was in a vacumm and around that water no heat transfer occured ( in theory) would it turn to ice eventually?

The problem is, there is no such thing as a "perfect insulator", as far as I know.

If there was such a thing as a perfect insulator, you might not have to constantly add heat to keep the water liquid.

But since there is no such thing as a perfect insulator, then indeed you apparently do have to constantly add heat to keep the water liquid.

I know of insulators that can slow down the heat loss, but I'm not aware of any that can stop it completely.

Or to put it another way:

if you had a volome of water that was in a vacumm and around that water no heat transfer occured ( in theory)

I know of no theory that would allow this. It wouldn't happen in a vacuum, Liquid water can't exist in a vacuum as this phase diagram shows (Vacuum pressure is at the bottom of the graph, it's either solid or gas (vapor), not liquid):

[atsimg]http://files.abovetopsecret.com/images/member/e19932c3ce6d.gif[/atsimg]

A vacuum thermos is a type of container that uses a vacuum to slow down the heat transfer of the container, but if you skip the container and put the water in a vacuum, you won't have a liquid any more.

reply to post by Arbitrageur


That'll teach me not to hack out a quick post without reading carefully first

Impressive post of yours btw and it deserves more credit.

Originally posted by Pilgrum
Impressive post of yours btw and it deserves more credit.

Thank you. I did put some effort into it, so it's nice to see it was appreciated.

I think the OP asked an excellent question and before writing that reply I read the whole thread, and then searched and found some other answers to similar questions on the internet, some of which talked about the molecular bond which was mentioned on this thread before I posted, but nothing really addressed the OPs specific question about the source of the energy.

I'm fascinated about energy sources like the exothermic process of water freezing, or the exothermic process by which the re-useable hand warmers work, that is a really cool application of science if you ask me, and the latent heat of fusion is also a key method of energy storage in those devices like it is in water, as described here:

How do those reusable hand warmers (where you click them and they start heating) work?

So if we can understand how those hand warmers work, we'll have a better understanding of how liquid water also stores energy via latent heat of fusion. It's a cool gadget related to the OP's question.

reply to post by Arbitrageur


Thanks for your responses. I was very impressed that someone would take as much time as you did. I will try to do it for someone else if the situation arises. Now we just need to figure out how to make the water give up its heat at our command.

So I have a site that will calculate the force of a hydraulic piston.
Hydraulic force
I tried to figure this all out but am having no luck.

Can anyone figure out the force in joules that an amount of water that was used in earlier post is equal or greater than the energy required to freeze water. I have tried but it is above my level.
Basically I want to see if the amount of heat needed to raise the temperature of water is equal to or less than the amount of force in joules that is produced by the force of freezing water.
From what I read on this thread the amount of heat required to thaw ice is equal to the amount of energy produced from the force of expanding ice in the same amount of water that turns to ice.
I am not to advanced in math and hope someone can show the math behind this. I believe all the answers are in this thread but I just can't put it together