Donald Hester
Washington State Licensed Home Inspector #647
WSDA#80050
InterNachi Member #NACHI10022401
509-670-9572
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Washington State Licensed Home Inspector #647
WSDA#80050
InterNachi Member #NACHI10022401
509-670-9572
Contact Us
DonHester's blog
When hot water gets cold, freezing pipes and the Mpemba Effect.
Submitted by DonHester on Sat, 01/07/2017 - 18:30.
When hot water gets cold, freezing pipes and the Mpemba Effect. Wenatchee Home Inspection
With winter putting it grips on the much the country a real issue becomes frozen pipes. Many may not know that your hot water pipes may be even more vulnerable to freezing quicker than the cold water pipes. Remember the key word here…”may”. This came up in a discussion in a meeting when a local Plumber Matt Bruggman of Plumb Perfect suggested that I may know why, referring to me as the resident scientist in the room (by the way I am not a scientist).
At first I thought, I have heard of it this but really did not know why it happens, and then I questioned myself, was it really true or just more folklore? That lead me to do a little research on this and what I found was even better than what I could have thought.
The phenomenon of hot water freezing quicker is due to what is referred to as the “Mpemba Effect” named after a Tanzanian student who in 1963 at 13 years old noticed that hot ice cream/boiled milk mix freezes faster than a cold one.
It turns out that one day Mpemba put his ice cream in the freezer at school when hot and found out that his ice cream froze before his fellow students who let theirs cool a bit first. Mpemba brought this to the attention of his physics teacher and was told “You were confused, that cannot happen”. Newtonian physics does not work that way… at least that is what they thought.
It was then during a holiday that Mpemba met a friend who made ice cream for sale and this friend confirmed that it was true that the hot mix of ice cream did in fact freeze faster. His friend was given this information from his brother, so it was known to these ice cream makers that the effect did happen and they used it to their benefit.
Now back in school it was said that Mpemba was teased for this question and they called it Mpemba physics. Mpemba did not let this stop him and when attending high school he again asked his next physics teacher the same question, he received this reply - “Well, all I can say is that that is Mpemba’s physics and not the universal physics.”
Mpemba was still not satisfied and decided to repeat the experiment. Performing the experiment he again, he did see the effect and still was yearning for an answer why did it happen.
Again not to be dissuaded and being persistent, when Physicist Dr. Denis G. Osborne from the University College in Dar es Salaam gave a lecture to his school Mpemba posed the same question again to Dr. Osborne. Dr. Osborne found that this seem unlikely, but since Mpemba stated that he had done the experiment and it did happen that he should not dismiss the claim right off. Dr. Osborne on his return to University College in Dar es Salaam had his research students repeat the experiment and this lead to a paper called “Cool” describing the “Mpemba Effect”.
Now it turns out that this effect has actually been known for a while and was first described by Aristotle who stated "The fact that water has previously been warmed contributes to its freezing quickly; for so it cools sooner. Hence many people, when they want to cool hot water quickly, begin by putting it in the sun".
Yet the best part of this is that the condition is not fully understood and there are still some questions on how exactly this phenomenon or effect takes place. It turns out to be more complex than most would ever think and it does not always happen that way. Yes sometimes the cooler water will freeze first.
The effect can be contributed to several factors such as evaporation, dissolved gasses, convection, surroundings, and supercooling. More recently a team of physicists from the Nanyang Technological University in Singapore are also proposing that some of the effect can be from manipulation or stretching of the hydrogen bonds and their subsequent release of energy as they relax during cooling.
This still does not fully explain the “Mpemba Effect” and it could be a combination of hydrogen bond effect, supercooling and evaporation. There will need to be more research performed to fully explain the phenomenon.
So the next time your hot water pipe freezes you can look at it and think about the physics that just happened… then call a plumber to get you back in business.
For more reading-
http://math.ucr.edu/home/baez/physics/General/hot_water.html
https://arxiv.org/pdf/1310.6514.
http://phys.org/news/2010-03-mpemba-effect-hot-faster-cold.html
http://www.sciencealert.com/why-does-hot-water-freeze-faster-than-cold-water
Mpemba and Osborne, "Cool", Physics Education 4, pgs 172–5 (1969)
“It isn't necessary to imagine the world ending in fire or ice. There are two other possibilities: one is paperwork, and the other is nostalgia.”
Frank Zappa
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NCW Home Inspections, LLC is a Licensed Washington State Home Inspection service located in Wenatchee Washington serving Chelan County, Douglas County, Kittitas County, Okanogan County and Grant County Washington and the cities of Wenatchee, Leavenworth, Cashmere, Oroville, Cle Elum, East Wenatchee, Quincy and many more…
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