Effects of Freezing Water

It's always a pleasure to help young guys to become lost as us in technical issues....

I was not able to locate something in the web that had not some commercial accent, so, I'd recommend the school library, at this level, I think would be the best place.

About the valves and pipes rating, it's resistance is defined by standard. ASME/ANSI B-16. For related information, www.engineeringtoolbox.com , besides this is not applicable to elementar level. Usually, the proof pressure in any equipment/installation/vessel is two times the working pressure for some reasons: provisions for tensions in misalignment and self-suporting, provisions for corrosion and damage margin, and for overpressure and water hammering, if occurs.

No, the ice does not continue to expand. The expansion of ice occurs due to the change in molecules arrangement from liquid to cristaline solid. It causes the water to occupy more space than when liquid. Then, as temperature continues to drop, it behaves as a normal solid, contracting.

http://hyperphysics.phy-astr.gsu.edu/hbase/chemical/waterdens.html

The call for repairs below 15F is because probably in this temperature the water inside the pipes freeze. It probably will not freeze until this temperature due to be somewhat protected inside the pipes, and flowing.

My thanks for your response. The second link was particularly helpful. Might the hexagonal matrix structure of the ice crystals be related to the crystalline structure of snowflakes, and do you think kids at this age would see the connection? Secondly, what is the structure of the water molecule in it's liquid state?

As you might have read: water has 13 different crystalline structures: depending on the solidification temperature the snow crystal will have a different shape.

It is also this effect of transition between crystal structures which makes ice expand till -4°C.

You can fill your whole science fair with water projects and nobody does the same.

Gwen

bh escobar is right on target. However it seems to me that you´re going in too deep for your 8 year old boys. Please resist the urge to do the project for them. Try not to get too technical or else you risk missing the whole point of the excersise, which is the learning experience itself.

I´d recomend doing two tests in paralell to illustrate the point. Make two identical rigs A and B. Rig B is left with the shut off valve partially open and valve on rig A shut closed.

Which one freezes first and why?

Most of the frozen pipes you generally see are inside someones house. It takes -15 or so to freeze the pipes because even though they freeze there was some heat by them that kept them from freezing sooner. The easiest form of show and tell would be to cap a chunk of pipe, put the ball valve on the other end,fill it up with water close the valve so there is no air inside then put it in the freezer for a couple days. Put it in a plastic bag so you don't make mama mad if anything leaks.(I don't want that dirty thing in the freezer by our food) (thats why it is in the bag) See if you can blow out the side of the pipe. They can take the blown out pipe to school to show and write up a story of how and what they did to come up with the results they got.

Good grief! Doesn't anyone remember what it's like to be eight? And how much grief a parent's help with science projects can bring--even to a 12 year old? The best advise to a child that age, is to tell them to think up something that will be understood by, and interesting to, someone else about their age--that is, to him or her self--not to try to just show off what they know (but really don't know). Observant parent can see any number of "project" ideas just by watching children attentively as they make unusual things happen around them--while playing, doing chores, or otherwise. Things like these are good starting points for projects; much better than plumbing projects, rupturing pipes, complex riddles that can't be witnessed or visibly demonstated, and such. For example, a pipe configuration can "conduct" sound from on place to another, or one ear to another, while a closed or closing valve between the ends can muffle of block the sound. This could demonstate, say, analogous switching functions. Or, blowing air into a conducting pipe configuration is easy and the air can be sensed at the other end. But, begin closing that valve and it becomes harder to blow into the pipe, while the air sensed at the other end become much weaker. A good analogy to resistance in an electric circuit? Much more fun to observe than a broken pipe and unbroken pipe in front of an explanation poster, wouldn't you say? And it doesn't take complex wording--something most eight-year-olds can neither conjure up or understand--to make the demonstration meaningful. Simply the kind of thing you might witness simply by putting pipe and valve in any child's hands to play with--playing either with him or her self, with siblings or pals, or even playing with a parent. More action, less verbiage--that's the key to a good science project.

Yes

ice will continue to expand until you reach

absolute zero

Water will become ice at 0°C and expand till it reaches -4°C. Then it will shrink, just as all other solid substance does when cooling down.

The fact that water has this special effect can be found in the crystal structure.

Gwen

Just a small correction.

Water expands from 4 C down to 0 C and cristalizes, and then starts to shrink as temperature goes down.

But it expands again to a minimal density at -4°C.

That is why freezing of water cracks rocks: it solidifies in the space that it has (pushing away the water that is to much, increasing the pressure in the network) and the next step is to expand until -4°C.

Water is a nice special exception on nearly every rule.

I seem to remember doing this with a rubber tube filled with water and sealed at both ends with a hose clip. take the temp down to different values and measure the diameter.

Reminds me of my attempt to create a good science project for my daughter who was in 2nd or 3rd grade. She was going to demonstrate some of the properties of water with a clay and toothpick model of water molecule to show why it was unique. The first was to charge with static electricity a large plastic salad tossing spoon with a nylon rag. Using a bowl to catch the water and pouring it in a narrow stream into the bowl from a pitcher, the charged spoon was to be used to cause the stream of water to deflect without touching it -- demonstrating water's polar structure. Next I magnetized a needle which could be floated on the water due to surface tension surface, with the side benefit that it pointed northward. Finally adding a little kitchen detergent would cause the needle to sink. Unfortunately another child bumped into my daughter's table, spilling some water. A teachers aide used the rag with a little detergent to mop up the mess -- so nothing worked.

My understanding is that the 'hot' water pipe freezes first.

Hot water will freeze before cold if it is exposed to the freezing air, where evaporation can take place.In a closed container, and all other factors being equal, this does not hold true.

The cold will freeze first in a closed container, or pipe, if the water has no movement.Many times, during the night, or day, the toilet is flushed,hands are washed, and the water in the pipes is replaced by warmer water from the street mains or underground well.At night, after bedtime, very little hot water is used, and the water in the pipes has a longer chance to freeze.

Water can be chilled below 0 C if the water is very pure, and the container is very clean.This is called supercooled water.If you tap the side of the container holding the supercooled water with sufficient force, it will create a cavitation on the inside of the glass, and an ice crystal will form, and others will form around it, soon, the whole container will freeze solid. A curious thing, when super chilled water freezes, the temperature rapidly jumps to 0 C.

A curious thing, when super chilled water freezes, the temperature rapidly jumps to 0 C.

This is perfectly normal: the energy that normally needs to be evacuated to freeze water at 0°C is still inside the supercooled water, when it solidifies the energy comes free and heats up the water to the freezing point, where the solidification will stop.

Want a simple example?

Never happen to forget a beer bottle in the refrigerator, that has frozen when you touched it with your hand?

Actually, the heat is casuse by latent heat of crystallization.Water can be both ice and water at 0 degrees C.In order to change from a liquid to a soild (a state change), an additional quantity of heat has to be removed.This is called latent heat. Latent heat is also involved when water changes from liquid to vapor, and visa-versa.This latent heat is what powers hurricanes.

By the way, 0 centigrade is really defined as when ice melts, not when it freezes. Many variables can affect freezing point, without affecting the melting point.

Thank you for the word: Latent, I did not find it in my head. (I'm not native English)

You are right on the definition of 0°C. It is also a practical solution: an ice bath is a constant source of 0°C (handy to do calibrations)

In fact water will always get into a supercooled situation as you need to start the crystallisation. Depending on purity and other influences the supercooled status will last shorter, be less present.

Salt water will freeze at lower temperatures but when the crystal resides between 0 and -4°C the salt will be evacuated. The salt ions/molecule is not compatible with the ice crystal and thus will migrate to the crystal borders, where the salinity goes up and this will melt the water again, flowing out of the structure, flushing away the salt.

The crystal growth in this 0 to -4°C zone makes the chrystal borders shift constantly, removing almost all the salt.

This might be a nice tech fair project: desalinization of water by freezing it.

You can make fresh water by circulating deep cooled salt water over a cooling surface/pin, the formed ice cubes are perfectly clear, where salt laden ice looks milky.

The circulation of the water takes the salt away and leaves only water molecules in the cube.

Ice cube makers use this principle (to get rid of the scale in normal potable water)

Gwen

Thanks Gwen! You have filled in some blanks in my knowlege of water/ice formation, and especially the way the salt is purged from sea wateri . I am always open for new info.

Did you find the definition of LATENT HEAT? Basically, it is the heat required to change any material from one energy state to another..this heat does not affect the temperature of the gas,liquid,vapor, etc, it simply provides the energy required to change state.Modern air conditioning systems use the latent heat of evaporation and condensation of Freon or Ammonia to transport heat from one place to another.

Google LATENT HEATfor more info.

I do know latent heat very well, it is only that I could not come to the word.

I'm working on a latent heat based heat storage system for home use.

The idea is to melt a paraffin style of product to be able to generate an amount of water at a constant temperature (until all the paraffin has solidified)

Paraffin melts somewhere between 60 and 70°C (depending on the exact composition). Do you know a good source of density, latent heat and risc info on different materials? (to select the best substance)

Gwen

Here is a link that may help

http://www.microteklabs.com/table.html

good luck!

Since you mentioned reference source, the triple point of water is also used as a precise reference for temperature.It is a closed vessel, with water in all 3 states:solid, liquid, and vapor.If the temperature attempts to increase, more ice melts, more water evaporates, and the temperature stays the same..that is until all the ice is gone.The opposite is true if the ambient temperature drops,more water freezes, more steam condenses, but the temperature remains constant.

NIST uses the triple point of various liquids and solids for reference temperatures, such as gold, platinum, etc. for high temperatures.

Thoughts that come to mind on the subject:

1. Use thin walled PVC as the pipe. I believe this would be easiest to crack

2. Use dry ice to cool the pipe. I believe it has a cooler temperature than your typical freezer.

3. Fill a second pipe with a 50% solution of antifreeze (like out of your car's radiator maybe?) and see that it doesn't freeze.

To keep things simple, use pipes about a foot long and GLUE pvc caps on the pipe with water (to keep from blowing the caps off when it freezes). Don't glue caps on the pipe with antifreeze (just press fit them) so you can easilly remove the cap and show that it is still liquid.

Be sure and use gloves. We don't need any frost bitten 8 year old fingers.

It might be kinda hard to do damage to a 600 psi valve by freezing water. I don't know.

This is all thoughts with no experience behind them so you might want to experiment ahead of time.

Bill

Sorry I strayed so far from your original request, sometimes I get off on a tangent.

Here is a link for some simple experiments with ice.

http://www.encyclopedia.com/doc/1G1-16646705.html