Author Topic: Freezing Speed of Hot Versus Cold Water  (Read 10757 times)

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Offline bostonmanTopic starter

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Freezing Speed of Hot Versus Cold Water
« on: February 18, 2022, 04:01:36 am »
Recently we had single digit temperatures approaching and decided to experiment with the freezing speed of hot versus cold water.

From research, hot water should freeze faster, but I didn't exactly get these results.

The outside temperature was approximately 20-25 degrees F (and deceasing slowly). I placed a piece of plywood across two sawhorses (to eliminate the ground from acting as a heat sink), placed two identical cookie tins on the plywood (spaced apart), used a piece of copper tape to hold the temperature probe on the bottom of each pan (I used two identical temperature data loggers), and, simultaneously poured tap water in one, and near boiling water in the other.

If my understanding of thermodynamics is correct, large delta temperatures will cool quickly and then slower as it gets closer to the ambient air (I believe technically they will never be exact). As an example, if I heated a steal block so it was glowing red, and placed it outside in 0 degrees F, it will cool very quickly in the beginning, and then slower and slower until it almost reaches 0 degrees F.

Having said this, if you look at my hot versus cold graph, the hot water seems to do just that. Leaving out the fine details such as just exactly what is going on with the molecules, from research, I expected the hot to freeze noticeably faster.

Looking at the zoomed in graph around 32 degrees F, the hot water technically froze before the cold, but technically they appear to have froze almost at the same time.

The temperature data loggers have a +/- of about 1.5 or 2 degrees (I don't have the specs at the moment).

Ignoring the error in the data logger and other differences, it seems very little difference exists between freezing hot water versus cold water. Also, I'll add that both cookie tins had a high amount of ice indicating the temperature was truly 32 - and they were both ice at near the same time.

Am I thinking of this wrong, or does the two technically freeze within a short time of each other and technically the hot beats cold but by a very irrelevant amount?
 
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Online bdunham7

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Re: Freezing Speed of Hot Versus Cold Water
« Reply #1 on: February 18, 2022, 04:21:39 am »
Did you weigh the water in each?   :)
A 3.5 digit 4.5 digit 5 digit 5.5 digit 6.5 digit 7.5 digit DMM is good enough for most people.
 

Offline bostonmanTopic starter

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Re: Freezing Speed of Hot Versus Cold Water
« Reply #2 on: February 18, 2022, 04:24:18 am »
Basically the same amount of water in each.

Both tins were filled to the same height.
 

Offline emece67

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Re: Freezing Speed of Hot Versus Cold Water
« Reply #3 on: February 18, 2022, 12:38:44 pm »
.
« Last Edit: August 19, 2022, 05:14:21 pm by emece67 »
 
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Offline strawberry

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Re: Freezing Speed of Hot Versus Cold Water
« Reply #4 on: February 18, 2022, 12:59:10 pm »
 

Online Zero999

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Re: Freezing Speed of Hot Versus Cold Water
« Reply #5 on: February 18, 2022, 01:02:03 pm »
What were the weather conditions i.e. wind and cloud cover?

If it's a clear night, the water will freeze quicker, than if it's cloudy, due to radiative cooling. The effective blackbody temperature of the sky is the more important than the air temperature. It's possible for the water to freeze, even if the air temperature is significantly above freezing.

Wind should provide evaporative cooling, although it's often more associated with cloud cover and the water will get mixed up more so ice might be less likely to form on the surface.

Temperature measurements don't always indicate the state of the water. It can be below 0°C, yet supercooled and still liquid.

 

Offline T3sl4co1l

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Re: Freezing Speed of Hot Versus Cold Water
« Reply #6 on: February 18, 2022, 01:44:53 pm »
How long for the curves to drop below 32F?

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Online jpanhalt

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Re: Freezing Speed of Hot Versus Cold Water
« Reply #7 on: February 18, 2022, 02:36:39 pm »
Basically the same amount of water in each.

Both tins were filled to the same height.

As the poster #2 suggested, volume/mass changes with temperature.  Start with the same mass in each tin.  See: https://www.usgs.gov/special-topics/water-science-school/science/water-density
 

Online Siwastaja

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Re: Freezing Speed of Hot Versus Cold Water
« Reply #8 on: February 18, 2022, 03:26:31 pm »
I don't understand this at all.

1) Your graphs do not show the point where both have completely frozen, even at the point of temperature sensor; this would be seen as the temperature going BELOW 32F; significantly, of course, because of measuring inaccuracies.
2) Your graphs however do show the point where the freezing, i.e., phase change starts, at the sensor site at least, which is AT 32F. This is WAY sooner for the cold water, I don't get it where you get the idea that "hot water technically froze before the cold", since the graphs don't show anything else than starting of freezing, and it happens much earlier for the cold sample: already around 17:20; hot is there at around 18:10.

The plot simply ends too early. Also having a few sensors per sample at different positions would be interesting.

This is all as expected from common sense; of course the hot water takes longer, because it needs to cool down to the same temperature as the cold sample is already at, at which point the power dissipation should be exactly same.

I'm aware of Mpemba's effect, but your measurement does not show it even if you expect it to. The harsh reality is, if this really was some "common knowledge" thing, it would be easy to recognize, not disputed, easy to replicate, and not named after a student making ice cream in 1960's. The Wikipedia page discusses this phenomenon quite well, so maybe you can try to find conditions recreating it because certainly the conditions need to be right. What you have now shows the complete opposite, and by large margin, so that I simply do not understand how you think by close zooming you can find it to prove your expectation.

You are aware that tiny differences in sensors and water mineral content easily shift the measurement of 32F by easily 1F? Yet you expect that the 31.75F measurement means freezing is over? Even though the same zoom-in shows it bounces back to tad over 32.0F? This is just sensor noise.
« Last Edit: February 18, 2022, 03:34:01 pm by Siwastaja »
 
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Offline Nominal Animal

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Re: Freezing Speed of Hot Versus Cold Water
« Reply #9 on: February 18, 2022, 07:20:49 pm »
It is essential that you have convection cooling and not just radiative cooling, because an important part of the phenomenon is rapid cooling.  You should also use distilled water, because boiling water in a metal container (kettle) can easily add to the mineral content, and any suspended particles can act like freezing kernels, throwing everything off.  Just add a bit of salt or sugar to the water, to see how drastically the results change.  Drinking water always contains quite a lot of minerals.

The Journal of Physical Chemistry published an interesting paper in 2015 by Jin and Goddard, Mechanisms Underlying the Mpemba Effect in Water from Molecular Dynamics Simulations.  The "force fields" mentioned in the paper are interaction models based on theoretical models with numerical values fitted to reproduce known observables (heat capacity and so on) for water; I believe even non-chemists/physicists can read it (and ignore any technical details) to get a grasp on what actually is involved here.

Kinetic energy in the form of heat is 'stored' in multiple degrees of freedom within a molecule.  Essentially, the atoms in the molecule vibrate in various ways as temperature increases – that (and of course the overall kinetic energy of the molecule) is where the energy in the form of heat is –, and more recently, ab initio simulations indicate that as water molecules are hotter, the length of the oxygen-hydrogen bond increases/weakens.  When rapidly cooled, the bond length shortens slower than some of the other degrees of freedom (angular vibrations at the same distance), and to put it simply, very recently hot water seems to have lower heat capacity.  (It is actually a bit more complicated than that, because it involves how these molecules interact with each other, and not just individual water molecules.)  It is not any kind of "memory", it is just another facet of the phenomena we rely with metals: annealing.  Water just happens to be an interestingly complex substance, where this kind of an effect occurs even in the liquid phase, not just in the solid phase.  Overall, water is definitely one of the most difficult to simulate (outside ab initio AKA quantum mechanical modeling of the interacting electrons), which also shows in how in the above paper they used multiple unrelated models to confirm their results.
« Last Edit: February 18, 2022, 07:25:04 pm by Nominal Animal »
 
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Offline SL4P

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Re: Freezing Speed of Hot Versus Cold Water
« Reply #10 on: February 18, 2022, 09:42:12 pm »
I remember this experiment from year 8 in school.
The significant factor is the ‘rate of change’, not the immediate temperature of the samples.
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Offline tunk

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Re: Freezing Speed of Hot Versus Cold Water
« Reply #11 on: February 18, 2022, 10:14:40 pm »
Were they both fully frozen when you stopped the test?
If they were, I would have expected a further drop down to ambient.
And it may have been better to put the sensors centrally in the tin.
 

Offline Rick Law

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Re: Freezing Speed of Hot Versus Cold Water
« Reply #12 on: February 18, 2022, 10:28:48 pm »

The Carl Sagan "standardard" : "Extraordinary Claims Require Extraordinary Evidence."

This "Mpemba effect" is an extra-ordinary claim.  It is trying to invalidate the "Intermediate Value Theorem" long established in mathematics.  For "Mpemba effect" to be true, the hotter one must get pass the temperature of the cooler one without ever taking on the temperature value of the cooler one.

I believe the "Mpemba effect" is a description of poor experimental techniquesHere is why:

Mpemba's observation was in 1963 by: "beakers in the icebox of a domestic refrigerator on a sheet of polystyrene foam".    A 1960 style refrigerator likely is fan-less inside and relies solely on convection to "spread the cold" within.   The evaporator may be directly connected to the ice box or is the ice box itself.  There is no way to ensure that the two beakers are under the exact same condition.  Even with modern refrigerators with fan-forced air circulation, you cannot ensure the conditions for the exact same physical spot will have the exact same condition over time.

"Beakers in the icebox" implies they were done together.   When you placed the two beakers in together, they cannot both be at the same spot.  Two different spots will have two different conditions.  Where is the inlet of the refrigerant (coolest)?  What else may be inside the refrigerator affecting circulation(s)?  Etc., etc

Let say I infer wrong.  May be the two beakers were at the same spot and test one after the other.  Again, conditions will be different for the two of them because they were there at different time.  Immediately, one can reason that with something hotter inside the refrigerator, the average temperature inside will be higher and the cooling motor must run more to force to cool the refrigerator's thermostat enough to shut down the motor.  So the hotter beaker was cooled more than the other.

For such " observation " to be useful, One must document in detail how the conditions for these beakers are controlled and how exact same-ness was attained.  Otherwise, one may just be observing the effect that cooling ability inside a refrigerator varies a lot, by time and by location.

If one place a thermometer inside a fridge, one would be amazed at how much the temperature really varies by time and placement.  I did, right after I replaced the defunct thermostats in my fridge to validate it works.  I still have the two digital thermostat connected: one sensor inside the freezer compartment and one inside the fridge compartment wired to displays outside.  So I have been observing the freezer/fridge temperature for 2-3 months now.

Furthermore, even what "freezing" means is not even defined in reporting this "observation".  This lack of definition is very sloppy!  Does it mean reaching freezing temperature?  Water at freezing temperature still need to loose more latent heat for phase change to complete there by turned solid.  The best way to check for phase change is when the temperature momentarily stops changing.  That "temporally constant temperature" tells the observer that phase change is occurring.  Is that what he means by freezing?  How is the phase change observed?

Hence my opinion: Poor documentation, poor understanding of physics experimental techniques, and poor definition.  Very sloppy indeed.  Good initiative and good curiosity however.
 

Offline Nominal Animal

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Re: Freezing Speed of Hot Versus Cold Water
« Reply #13 on: February 19, 2022, 12:04:03 am »
For "Mpemba effect" to be true, the hotter one must get pass the temperature of the cooler one without ever taking on the temperature value of the cooler one.
No; must pass the temperature of the cooler one while having smaller thermal capacity than the originally cooler one.

One of the experimental verification methods is to choose a temperature, say +27°C = 300 K.  Put say 200g of pure water in a stoppered beaker in a temperature bath for say a half hour.  In a column, boil pure water and have it run through a powerful cooling sleeve (a pipe inside a pipe, with the coolant running in the outer pipe), at such a flow rate that the output is very close to the target temperature, and measure the exact same amount into an identical beaker.

At this point, you should have two beakers with the same amount of pure water at the same temperature; the only difference being that one has been at that temperature for some time, the other just flash-cooled from near boiling.

Then, put the two into the same liquid nitrogen bath (-196°C = 77 K), and measure the temperature changes in the two.
The current understanding is that indeed, one will cool faster than the other; and this is what the "Mpemba effect" actually refers to.

For reasons why, see my earlier post.  If you need clarifications, I'd be happy to elaborate; it is interesting but complicated, surprising but not that weird at the atomic level.  It's like the fact that solid water is less dense than liquid water at +4°C = 278 K.
 

Offline rfeecs

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Re: Freezing Speed of Hot Versus Cold Water
« Reply #14 on: February 19, 2022, 02:45:02 am »
 

Offline bostonmanTopic starter

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Re: Freezing Speed of Hot Versus Cold Water
« Reply #15 on: February 19, 2022, 03:13:15 pm »
I need to read these replies deeper and check out the links, but wanted to expand on a few things.

One person stated my graphs don't make any sense, others commented about wind, etc... I understand many factors play into temperature from the obvious differences to minute molecular physical changes. Was my experiment ideal? Absolutely not, but it was enough to get a visual on what happens. By the way, the temp loggers I used were: Elitech URC-4 Temperature Logger taken at the quickest polling rate of 10s.

The reason the data got "cut off" was to bring the items inside because it was getting late. Both cookie tins were frozen and both meters showed 32 (or nearly 32). The experiment was to see which one froze quicker and since both were at "32", they both were full of ice, etc... I brought them inside.

My experiment was to see which froze faster, but, due to too many anomalies, including the error from the meters, all I could do is see which reached "32" the quickest. From reading over the years, I expected to see a significant difference such as the cold water still being liquid and the hot water being ice.

Also, maybe this was already confirmed or rejected (again, I need to read through the responses better), but my understanding  is that the greater the temperature delta, the quicker something will change to become equal, but will slow as it reaches the other temperature of the other object. As an example, if I came in from a snow storm and removed my wet coat, it will try to reach room temp quickly in the beginning, but will slow the closer it gets closer to the ambient temp (and I think ideally it will never reach the "exact" room temperature due to what occurs at the molecular level).

My graph shows this happened: the hot water cooled very quickly and slowed as it approached 32 while the cold water had a much slower decrease because it was closer to ambient. Again though, my experiment wasn't meant to be specific and exact, it was to see which cookie tin was still liquid after the other became ice.

The more I thought about things, the more I realized, there is little difference between where the hot water temperature begins. If I heated the water to one degree F hotter than the "cold" water, it would still take just as long to freeze from that temperature as if it started at 200 degrees F and decreased to 1 degree F hotter than the cold water.

My conclusion (excluding for a moment what happens at the molecular level): with a typical cold environment such as a freezer or a cold winter night, if I want to make ice quickly, starting with hot or cold water isn't going to make a significant difference as to when ice is achieved.

My graphs show that (assuming the meters are 100% accurate) that the hot water dropped to 32 while the cold was 32.1, however, both were almost a chunk of ice. I'll read through all the replies, but wanted to clarify that I'm not taking my measurements as fact, but more of a rough visual and didn't exactly get the results I expected.
 

Online Siwastaja

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Re: Freezing Speed of Hot Versus Cold Water
« Reply #16 on: February 19, 2022, 04:05:58 pm »
One person stated my graphs don't make any sense

Your graphs are completely as expected and make perfect sense: it shows that the cold sample starts freezing significantly earlier than the hot sample. It's just that your trace ends at some point during freezing. Neither sample is fully frozen at the end, because both end up at 32F plus minus tiny amount of noise.

The only thing that did not make sense are your comments; it's like you are looking at something completely different than what you posted?

Actually deciding when the freezing is complete is quite difficult. The ice does not conduct heat very well and convection stops, so once the water is partially frozen, you don't know how much of it is frozen. If the sensor is in the middle of the tin, chances are high a good indication of being totally frozen is temperature reading starting to drop again, significantly below 32F. This would overestimate the time, though, because heat transfer through the block of ice is slow. Do place the sensors consistently, in the exact same place, in the two tins to compensate for this.

You can't visually see if a block of ice is fully frozen. Try to drill a hole in it and liquid water may spurt out from the middle. State change is difficult because it happens at constant temperature: you can't see from temperature measurement how much frozen it is. The only way you surely know is to place gazillion of sensors and verify all of them measure below 32F (significantly enough to account for noise and inaccuracies in sensors, and the freezing point itself).
« Last Edit: February 19, 2022, 04:15:02 pm by Siwastaja »
 

Offline rfeecs

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Re: Freezing Speed of Hot Versus Cold Water
« Reply #17 on: February 19, 2022, 08:30:51 pm »
The article from the video:

"Questioning the Mpemba effect: hot water does not cool more quickly than cold"

https://www.nature.com/articles/srep37665

Quote
Abstract
The Mpemba effect is the name given to the assertion that it is quicker to cool water to a given temperature when the initial temperature is higher. This assertion seems counter-intuitive and yet references to the effect go back at least to the writings of Aristotle. Indeed, at first thought one might consider the effect to breach fundamental thermodynamic laws, but we show that this is not the case. We go on to examine the available evidence for the Mpemba effect and carry out our own experiments by cooling water in carefully controlled conditions. We conclude, somewhat sadly, that there is no evidence to support meaningful observations of the Mpemba effect.
 

Offline Rick Law

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Re: Freezing Speed of Hot Versus Cold Water
« Reply #18 on: February 19, 2022, 08:53:58 pm »
...
Also, maybe this was already confirmed or rejected (again, I need to read through the responses better), but my understanding  is that the greater the temperature delta, the quicker something will change to become equal, but will slow as it reaches the other temperature of the other object.
...
The more I thought about things, the more I realized, there is little difference between where the hot water temperature begins. If I heated the water to one degree F hotter than the "cold" water, it would still take just as long to freeze from that temperature as if it started at 200 degrees F and decreased to 1 degree F hotter than the cold water.

My conclusion (excluding for a moment what happens at the molecular level): with a typical cold environment such as a freezer or a cold winter night, if I want to make ice quickly, starting with hot or cold water isn't going to make a significant difference as to when ice is achieved.
...

re: "...maybe this was already confirmed or rejected...my understanding  is that the greater the temperature delta, the quicker something will change..."

Yup, confirmed by various replies by multiple people already.

re: "...starting with hot or cold water isn't going to make a significant difference as to when ice is achieved..."

That is the "latent" heat.  The "latent heat of fusion" of water to ice (phase change) is much greater than heat capacitance of water.

-  It takes 1 calory to heat 1 gram of water by 1 degree C.
-  It takes 80 calories for 1 gram of water to phase-change between ice and water (latent heat of fusion).
-  It takes 540 calories for 1 gram of water to phase-change between steam and water (latent heat of evaporation).

For 1 gram of water to phase-change between water and ice, it could change the temperature of water by 80 degrees C.  That is why I was so critical of the lack of definition of "freezing" when "Mpemba's observation" was made -- it takes 80x the heat exchange of dropping 1 degree verse for it to fully freeze.  When big things are wrong, the details hardly matter - this is the scale of worrying about minutes when hours are wrong.

By the way, interesting to bring up one point here. Calories (with capital C used for food) is 1000x calories (lower case C used in Physics).  Some "food science" people must have needed glasses when they first adopted the Physicist's unit of calories.  Someone must have mixed up g and kg by mistake.  So 1 Cal heats 1kg of water 1 degree in food "science" whereas 1 cal only heats 1 gram of water 1 degree.  Your bottle of Coke at merely 240 Calories is really 240,000 calories!  (No wonder I am getting fatter 1000x faster than I feel I should.)
« Last Edit: February 19, 2022, 09:01:41 pm by Rick Law »
 

Online Siwastaja

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Re: Freezing Speed of Hot Versus Cold Water
« Reply #19 on: February 20, 2022, 11:14:11 am »
Just forget about calories. They have no place in science or engineering.
 

Offline bostonmanTopic starter

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Re: Freezing Speed of Hot Versus Cold Water
« Reply #20 on: February 20, 2022, 05:11:06 pm »
Quote
re: "...maybe this was already confirmed or rejected...my understanding  is that the greater the temperature delta, the quicker something will change..."

Yup, confirmed by various replies by multiple people already.

I read these messages more thoroughly than now that I had time to devote in front of the computer (sometimes I scan the messages on my phone while out so I have time to process what is being explained).

I think the answer was provided by methods of more wording within explanations, but at least it confirms my initial understanding of the larger the temp delta: the greater the temp delta the quicker it changes and slows as it gets closer to the other object (room temperature in this case as per my previous example).

Maybe for a moment we should forget about actual freezing because the physics behind ice is more complex than I thought. I'll openly admit, I wanted to keep the data going for much longer than what my graph shows. Once I saw the outside temp was about 25 degrees F and expected to drop, I realized this could be my one last opportunity before winter passes to conduct this test, however, I expected the water to freeze much quicker. Due to thinking it would freeze quicker, I set up my area in an inconvenient location and in open view mid-afternoon. Once it turned night, I feared if I kept things setup throughout the night, animals might disturb things and/or someone may see the setup and enjoy two free saw horses (not that I live in a bad area, but someone did steal my garden hose and reel one year).

In any case, I made the assumption that seeing "ice", and 32 degrees F on the meters, was enough data to conclude what happened. Everyone is correct and that the tins weren't a solid chunk of ice (but they were quite solid), but my conclusion at a gross level was: hot water and cold water both reached "32" at nearly the same point (again, let's forget about actual freezing for a moment).

The other portion of my conclusion: If I had friends coming over and was out of ice cubes for drinks, starting off with hot water isn't going to provide ice cubes significantly quicker than plan old cold (tap) water. What I also knew before the experiment: if I place hot water in my freezer, I'm going to heat the freezer thus making the freezer work harder. Obviously this is why I conducted my experiment outside as one tin of hot water isn't' going to rob the Earth of cold.

Another reason I removed the test rather than keep it into the night: I knew many portions of my setup weren't ideal. As someone pointed out, multiple temperature probes placed in various areas would be ideal and all probes in the same locations in both tins; but also, the plywood the tins sat on were a heat sink, the data loggers aren't perfect, etc...

I expected to see a significant difference in temperature once one of the tins got close to 32, maybe something like the cold was 38 and the hot was 32 and it was clear hot or cold "freezes" faster than the other. Once I saw both tins had a significant amount of ice and it seemed both tins got there at nearly the same time, I figured at a gross level, I concluded hot versus cold have little affect on how long it takes to freeze.

Maybe my statement of using "freezing" was overboard. At a common sense level, I realize water doesn't always freeze as expected and at exactly 32. Now that I've read some technical reasons, I have a better understanding why. Having said this, it was probably wrong to to use absolute statements like "froze".

Based on my graph, and leaving out that my tins weren't technically "ice", I feel both reached an end point nearly the same time. Now at an atomic and physics level, and water impurities, I can't make any serious conclusions on which actually froze (and froze solid) quicker.

This experiment is from something that occurred years ago. My friend needed ice cubes and used hot water telling me hot water freezes faster. Over the years I've kept wanting to conduct such an experiment.

I think it's safe to say, if I have a friend that tells me using hot (tap) water is going to provide ice cubes much quicker, I know this will not be the case.



 

Online Siwastaja

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Re: Freezing Speed of Hot Versus Cold Water
« Reply #21 on: February 20, 2022, 05:18:41 pm »
but my conclusion at a gross level was: hot water and cold water both reached "32" at nearly the same point

But this is what I really struggled to understand. Like, are we looking at the same graphs? Because the graph you posted shows the cold one reached 32F at 17:15, and the hot sample at 18:15, roughly. Seems a big difference to me!
 

Offline bostonmanTopic starter

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Re: Freezing Speed of Hot Versus Cold Water
« Reply #22 on: February 20, 2022, 05:37:30 pm »
Oh, I understand your statement now.

You're correct, the cold water is 32 F sooner than the hot. I still feel due to many factors, it's close enough to conclude at a gross level you can't gain freezing time from starting off hot or cold.

But yes, you are absolutely correct, the hot water was still hotter than the cold and therefore took longer to "freeze"; clearly an error on my verbal statements versus the graph.

edit: I attached an expanded section of the graph
 

Online Siwastaja

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Re: Freezing Speed of Hot Versus Cold Water
« Reply #23 on: February 20, 2022, 06:23:19 pm »
It could even be that the hot sample starts freezing as late as 19:10 or so, it's hard to say!

Mentally shift the red graph up by 0.25F (assuming sensor offset error, or small differences in mineral content) and you see what I mean: doesn't it replicate what the cold sample did earlier, even including that interesting "overshoot" which bumps back up again? (Someone more familiar with small-scale effects not well explained by the simple equations could comment whether those overshoots and bouncebacks are actual, or measurement artifacts.)
 

Offline BeBuLamar

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Re: Freezing Speed of Hot Versus Cold Water
« Reply #24 on: February 20, 2022, 11:47:06 pm »
Assuming the outside temperature is constant. The initial cooling rate of the hot water is faster but it's hotter so it has to cool down to the same temperature as the cool water at which time the rate of cooling is the same as the cool water when it started but now the cool water is cooler. So no you do not see the hot water reaches the outside temp before the cool water.
 


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