A half inch copper tube is filled with water like in a garage to
supply a hose hook up.  How low a temperature has to be reached to
cause a rupture of the copper tube?  Is time a factor?

It happens at the temperature of zero degrees centigrade ( -32 F).

When water freezes, it's volume increases and that causes the rupture.

Time is not a factor.



There are some assumptions, which are satisfied in a garage:
  If water is not pure (has disolved salt) temperature will shift,
  if you are have extreme rates of cooling (fraction of a second) 
 time may become to play role,  and answer could be different.

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Clarification of Answer by hedgie-ga on 26 Oct 2003 13:22 PST

Lisound
I need to correct a sign. Sorry about that.

The freezing point is at +32 F, not -32F as stated above.

The conversion shown is here:
http://vathena.arc.nasa.gov/curric/weather/fahrcels.html

and discussion of  freezing point depression, by salt is described
here:
http://ask.yahoo.com/ask/20030619.html

And here are some data on the volume
change:http://www.bbc.co.uk/nature/blueplanet/ends/further_experiments.shtml


SEARCH TERMS
freezing point depression
F C conversion

hedgie

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Clarification of Answer by hedgie-ga on 28 Nov 2003 15:16 PST

Hi lisound

            The way this GA thing works, I get e-mail when you post an RFC
(Request For Clarification) and then, of course, I do clarify any
remaining issues. I do not get an e-mail on comments and so I did not
see yours:
 
"Where between 32 and 25 is the force of expansion great enough to
rupture a standard weight half inch copper tube?" 

until  now. If it is still of interst, I will look into it.

  For now I will just make a quick comment on the
comments we got:

 Maximal density is at +4 C. So water expands SLOWLY as we cool from 4 to 0.
 Then it jumps. We know that ice floats so that 90% of an icebergs is
submerged in the cold water. And yes, water in a pond is stratified -
with most dense water at the bottom (at equilibrium).

 Slow expansion (during  4 to 0 C) will not burst a  METAL pipe.
 It bursts on the jump in density- at the freezing point.
 
  When I said: "time is not a factor " 

I meant

   The rate of cooling will not afffect the Freeze point T.f
  
 That does not mean that if your put a pipe in a freezer for 1 minute
 or 10 hours, it will not make a difference.

In one minute the pipe does not have a time to equilibrate with the enviroment
and so water in the pipe does not have time to reach the T.f (freezing point)

To be exact, the term 'Temperature of water in the pipe'  is not well
defined until the system equlibrates, and temperature of water in the
pipe is (reasonably) uniform.

 So you do have one time constant here, which can be estimated by a complex
calculation, but is likely irrelevant for the slow cooling we get
during a winter night.

The T.f depends on the pressure VERY slightly. Again, the exact solution
would be quite involved, a way beyond $5 GA question, and exact number
would depend on geometry and material and - in this case - possibly on rate
of cooling. 
But, I can get you some estimate. It would help if you would specify
(guesstimate) the burst strength of your pipe and if we limit ourself
to 'slow cooling rates' - few degrees per hour or less.

  On the practical side: I had a good experience with putting 
(danish) 'warm tiles' in the garage and  now I do not have to worry
about freezing. More on request.

      If you are happy with the answer, please do rate it . It helps me 
     to improve my skills if I know how well,or how badly, I did answer.
     If you are not happy, please do ask for clarification.
     
     hedgie

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Clarification of Answer by hedgie-ga on 01 Dec 2003 09:40 PST

Glance on the graph at
http://www.lsbu.ac.uk/water/phase.html

at the  line dividing  liquid and solid

being traight vertical up at least to E6 Pa shows that effect
 of pressure is negligeable for practical purposes.

So question to
 Where between 32 and 25

answered just by eyeballing the graph, appears to be 
between 32 and 31 F.

Max density of water = 4-celsius at 1 atm pressure.  Really wimpy pipe
filled at 4-celcius could break at 3-celsius.

The original response reported that the pipe wopuld burst at 32
degrees F.  It ignores the fact later brought out that the frozen
water (ice)continues to expand reaching a maximum volume at minus 4
degrees C.  The one comment states that this is the "maximum density"
when it really should say, "minimum density" since the same amount of
water is taking up more space.  To continue, the minimum density point
converts to about 25 degrees F.  I would expect little volume increase
at 32 degrees increasing progressively at the temperature drops to 25.
 Where between 32 and 25 is the force of expansion great enough to
rupture a standard weight half inch copper tube?  Incidentally the
link to the experiments was very interesting and it also correctly
states the density change correctly.

is min density at -4C ?
i just know max density is at +4C
that's the temp at the bottom of a frozen lake.
chilled water starts expanding at 40F.

Of course time is a factor.  Everyone knows that if you just put the
ice cube tray in the freezer for a minute, it will still be full of
liquid water.  If the temperature in the garage drops low enough to
burst your pipes, but doesn't stay there very long, the pipes won't
burst.  Also, the temperature at which water freezes decreases as the
pressure increases.  See

http://www.chemistrycoach.com/Phase_diagram.htm

The freezing temperature decreases very slowly as the pressure
increases, but copper tubing is quite strong.  For a length of tubing
with no defects, it takes about 4000 PSI, or nearly 300 atm.  This is
for 1/2" nominal Type L hard copper tubing, which is the most common
in residential plumbing.  (Type L 1/2" tubing has a wall thickness of
.04", or 1mm, and copper has a tensile strength of about 400 MPa).  If
the pipe is Type M, it takes even more pressure. So the temperature
required for bursting may be several degrees below 0 C. 
Unfortunately, I haven't immediately found precise info on the
dependence of freezing temperature on pressure, so for now, your
question remains unanswered.