Which freezes first?

nicholas bonham-carter

the hot water pipe or the cold?
https://www.sciencenews.org/article/physics-new-experiment-hot-water-freeze-faster-cold-mpemba-effect

STEVEusaPA

Seemed like a lot of work and a complete waste of time.
Every winter during a deep freeze, some goofy weather person HAS to throw a glass of (usually warm/hot) water up in the air to show it freezing before it hits the ground.

Zman

Back in 2008 when there were tons of incorrectly winterized foreclosed homes freezing up, I sure seemed to me that there was more freeze damage on the hot pipes than the cold.
I was hoping the article would explain why...

Ironman

I think whether it's under pressure or open to the atmosphere has something to do with it. As Zman stated, it seems like hot water lines freeze more often than cold.

I remember discussing this with someone over 40 years ago. We decided to fill ice trays with an equal amount of hot or cold water and put them in the freezer. The cold ones froze first.

nicholas bonham-carter

Maybe it’s due to the deoxygenated water coming from the hot water heater.—NBC

unclejohn

The greater the ^t the faster the heat transfer. @Zman if the homes were winterized I would guess that the heat was off and so would be the HWH. So both hot and cold pipes would be the same temp.

rick in Alaska

The theory I heard, was that hot water molecules are farther apart, so basically has more surface area exposed, so it will freeze faster. Haven't verified it myself.
Rick

Larry Weingarten

Hi, I had heard that hot water put into a tray in the freezer would freeze faster because it would melt the frost and have more surface area to contact than cold water. Here's an article explaining that and more: https://futurism.com/science-explained-hot-water-freeze-faster-cold-water

Yours, Larry

hot_rod

I've also read that hot water freezes faster because it has less air from being heated. That makes some sense as you can see air bubbles rise from water when heat is applies.

unclejohn

I got the same result as ironman when I tried that experiment.

ethicalpaul

rick in Alaska said:

The theory I heard, was that hot water molecules are farther apart, so basically has more surface area exposed, so it will freeze faster. Haven't verified it myself.
Rick

But on its way to freezing, it matches the temp of the cold water pipe, right? Then it's just two pipes with the same temperature water in them.

One possibility is that cold water is used more often, so it's getting 50 degree water pulled through those pipes more often, which then have to get re-cooled toward freezing.

But hot water can sit idle for a lot longer and become freezing water.

Ironman

That was always my thinking on it.

Hot water molecules may move faster and give up heat quicker, but when they reach the same temp as the cold, the playing field is level except the cold already was closer to the goal (freezing).

EdTheHeaterMan

Perhaps the government can spend half a billion dollars on a study to explain what nobody cares about.

Nevermind, they are already doing that in so many other ways.

dopey27177

Why does a hot water pipe freeze first in building.

1. cold water piping is used a lot more frequently than hot water.
also in most houses there is leakage from toilet tanks where a flush valve needs repair or the float needs to be adjusted.

2. hot water piping has stagnant water in it because of lack of use. So the hot water pipe becomes room temperature.

In buildings where there is a possibility of freezing pipes people heat trace and insulate the cold water pipe and forget that the hot water piping is subject to freezing.

Jake

HomerJSmith

dopey27177, hot water pipes don't freeze in a building. If it's hot it doesn't freeze, but, I know what you're saying.

Water freezes when the BTU's or heat energy is extracted from the water to the point where the water becomes solid.

An earlier post about whether hot water or cold water in a refrigerator ice tray freezes first. Well, the thought was that the hot water freezes first because the hot water melts the insulation frost barrier between the evaporator and the tray in which the melting allows faster transfer of heat energy in the tray to the evaporator. As Larry stated.

All things being equal, cold water freezes first as the BTU's, aka, heat energy that needs to be extracted to make water a solid, is less.

nicholas bonham-carter

I’m still convinced that the water in the hot line, (when cooled to room temperature),, will freeze first due to the absence of dissolved oxygen in the water. Or it could be more likely to expand and break the pipe.
Maybe water which has been through a reverse osmosis filter will even be quicker to freeze.—NBC

ethicalpaul

I await the results of your experiment! Boil some water, put it in a container identical to a container with the same amount of "regular" water

then put them in the freezer and see what happens. Freezers have cold spots, so run the experiment twice, but swap the locations to see if the results are consistent.

nicholas bonham-carter

Not only is there the question of which freezes first, (room temperature hot water, or cold water); but also, which will expand the most, and break pipes.
The dissolved oxygen in the cold water might provide a cushion against breakage.—NBC

ChrisJ

I'm still convinced it doesn't matter which freezes first, pipes should never be allowed to get within 10 degrees of that point.

Solid_Fuel_Man

@ChrisJ 's steam pipes dont freeze. 

Water pipes freeze before steammm.....

ChrisJ

Solid_Fuel_Man said:

@ChrisJ 's steam pipes dont freeze. 

Water pipes freeze before steammm.....

Technically I think you can freeze steam but that's above my pay grade.

But I do wish I had thought of saying that.

icy78

I've always thought of it this way. If you have 2 equal open containers, one with say 130 degree water in it and the other one with let's  say it's 60 degree water,  that the hot one will evaporate rapidly and end up with less water to freeze and so the "hot" one will freeze first. This is assuming that the temperature of the hot container matches that of the cool container before reaching freezing.

ethicalpaul

icy78 said:

I've always thought of it this way. If you have 2 equal open containers, one with say 130 degree water in it and the other one with let's  say it's 60 degree water,  that the hot one will evaporate rapidly and end up with less water to freeze and so the "hot" one will freeze first. This is assuming that the temperature of the hot container matches that of the cool container before reaching freezing.

How much earlier did it freeze in your test?

HomerJSmith

Wild unscientific speculation runs well on this site, I see.

Taken to it's logical conclusion, boiling water should freeze first as it is certainly hot, in fact more hot than 130 deg water, making it the clear winner in the cool down race.

I have a bridge in Brooklyn I would like to sell you. Because of unforeseen circumstances, I can sell it to you really cheap.

nicholas bonham-carter

Take two identical glass bottles, and fill one with boiled water, and the other with cold water, and label which is which. Let both go to room temperature, and then put into a plastic bag in the freezer. See if one will break the glass and the other will not.
I think the theory that hot water pipes freeze first is because in pipe runs in an outside wall, the hot pipe is more likely to break, but not the cold pipe.
My theory is not due to freezing first, but rather, one expanding more due to no cushion of dissolved oxygen.—NBC

icy78

ethicalpaul said:

I've always thought of it this way. If you have 2 equal open containers, one with say 130 degree water in it and the other one with let's  say it's 60 degree water,  that the hot one will evaporate rapidly and end up with less water to freeze and so the "hot" one will freeze first. This is assuming that the temperature of the hot container matches that of the cool container before reaching freezing.

How much earlier did it freeze in your test?

I didnt try an experiment @ethicalpaul.
Its purely speculation, or maybe "wild unscientific conjecture"! 🙂

EdTheHeaterMan

@icy78... Did you allow for the coefficient of the factor relating to the difference in the square root of the binomial integer in relating to the wild unscientific conjecture? @ethicalpaul might be interested in the answer.

ethicalpaul

I did the experiment but I missed observing when the test pans went completely solid. But I can share what I learned and my notes.

What I learned is the time to get the water from Room temp to 32 is much less than the time to get it from 32 to frozen solid. I knew going in that phase change takes a lot of energy/time but I didn’t have a good idea of the scope of this.

what this means is the time to get them both to 32 is short. The hot water took 30 minutes more in my experiment to get to 32 but then hundreds of more minutes had to pass before either one froze solid. 

This has the effect of making the race be very tight to the finish. I suspect the cold water got to solid first, but maybe only by minutes. Nothing in my observations showed the hot water getting there first. I’ll run it again some day after my boiler is installed.

Here are my notes:

Left container: Cold tap water placed on counter while other water was heated.

Right container: cold tap water that was heated on stove in saucepan and held at full boil for 3 minutes, then immediately poured into container

Containers identical and filled to same mark, placed in freezer at same time. Freezer digitally set at 0f.

10 minutes: some evaporating condensate visible above right container

20 minutes: no visible evaporation. No ice observed in either container.

30 minutes: Ice starting to form at corner of left container. No ice observed on right container.

40 minutes: Ice covering left container. No ice observed on right container.

50 minutes: Ice continues to cover left container. Ice starting to form on corner of right container

60 minutes: Ice continues to cover left container. Very thin watery ice on right container.

70 minutes: Ice continues to cover left container. Very thin watery ice on right container.

80 minutes: Ice continues to cover left container. Very thin watery ice on right container.

90 minutes: Ice covering both containers. Ice appears much thinner on the right container.

100 - 210 minutes: Ice covering both containers.

220 minutes: left container solid on one side. Right container similar pattern

230 minutes: same as above

(Observations end)

Solid_Fuel_Man

That phase change is pretty interesting stuff, just like from 212F to steam. Simply changing water's temperature is linear, but make is change state takes a lot more energy. 

I would this same thing applies to steam, as well as refrigeration and even vaporizing LP. 

Jean-David Beyer

Ages ago, the (then) US Bureau of Standards decided to test whether hot or cold water froze faster. So they made the tests and the cold water froze faster. They then realized that, as scientists, the ensured that their freezers had all been defrosted before each test, and that the typical home freezer was not defrosted. So the allowed ice to build up in their freezers and re-ran the tests. In the new tests the hot water froze faster. They realized that the cold water trays made poor contact with the freezer, just touching three high points of the ice, whereas the hot water trays melted the peaks of ice and made good contact.

The only time I had a water pipe freeze was after I had my kitchen remodeled and the contractor had to relocate a lot of pipes. And they had to run in an outside wall. Well, his workmen were pretty sloppy and I caught them putting the insulation in only after the pipes were run, so they were uninsulated. I got them to fix that but I must have missed one. So that particular pipe has been known to freeze when the outside temperature goes down to about 2F which is rare. If I open the cupboard doors and put an electric heating pad on the hot water pipe where it enters under the sink, the pipe in the wall does not freeze.

nicholas bonham-carter

So did the hot water jar break, and not the cold one?—NBC

ethicalpaul

I didn’t use jars, I don’t want broken glass in my freezer!! But water increases volume when it freezes, I bet both would break. Let me know your results!

ChrisJ

Which weighs more.   12 cubic foot of ice or 12 cubic feet of water.   

Solid_Fuel_Man

Ice floats, so 12 cubic feet of water weighs more 

icy78

ethicalpaul said:

I did the experiment but I missed observing when the test pans went completely solid. But I can share what I learned and my notes.

What I learned is the time to get the water from Room temp to 32 is much less than the time to get it from 32 to frozen solid. I knew going in that phase change takes a lot of energy/time but I didn’t have a good idea of the scope of this.

what this means is the time to get them both to 32 is short. The hot water took 30 minutes more in my experiment to get to 32 but then hundreds of more minutes had to pass before either one froze solid. 

This has the effect of making the race be very tight to the finish. I suspect the cold water got to solid first, but maybe only by minutes. Nothing in my observations showed the hot water getting there first. I’ll run it again some day after my boiler is installed.

Here are my notes:

Left container: Cold tap water placed on counter while other water was heated.

Right container: cold tap water that was heated on stove in saucepan and held at full boil for 3 minutes, then immediately poured into container

Containers identical and filled to same mark, placed in freezer at same time. Freezer digitally set at 0f.

10 minutes: some evaporating condensate visible above right container

20 minutes: no visible evaporation. No ice observed in either container.

30 minutes: Ice starting to form at corner of left container. No ice observed on right container.

40 minutes: Ice covering left container. No ice observed on right container.

50 minutes: Ice continues to cover left container. Ice starting to form on corner of right container

60 minutes: Ice continues to cover left container. Very thin watery ice on right container.

70 minutes: Ice continues to cover left container. Very thin watery ice on right container.

80 minutes: Ice continues to cover left container. Very thin watery ice on right container.

90 minutes: Ice covering both containers. Ice appears much thinner on the right container.

100 - 210 minutes: Ice covering both containers.

220 minutes: left container solid on one side. Right container similar pattern

230 minutes: same as above

(Observations end)

@ethicalpaul That is interesting. I think that in my mind-pictures of pans used, (if I were doing the experiment) , I see using large pans. Say 3' x 4'. That way there is a possibly large amount of evaporation. And a possible different result.

On the other hand, if one were to use say, test tubes, the evaporation rate difference would by negligible.

You have some time on your hands!🙂