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Mugwump asked in Education & ReferenceTeaching · 1 decade ago

A question for High School Science Teachers?

I have noticed many people have a misconception about heat transfer.

"Which freezes faster, hot water or cold water?"

Most people that I ask this to say that the hot water freezes faster. How can it be that so many people are misinformed? When I ask where they got such a crazy idea, they always say the same thing. "From my high school science teacher". (I just asked the question here on yahoo and got a 90% hot water answer)

How can we spread the truth to the average science teacher? Do you all have a newsletter or something?

It makes me cringe when I think about the wasted electricity as millions of people fill ice trays with HOT water and put them in the freezer.

(Please don't quote the Mpemba thing. What that says is that it is possible, that you might get cold water to freeze faster occasionally, not that it is the rule, that it is an exception. And in it the "theory" states that external factors may be responsible, duh. Like putting one sample closer to the freezer vent.)

Please help save energy, teachers.

Update:

I am a mechanical engineer (we are the ones who study Thermodynamics).

If what you say is true about the time your teachers allowed you to spend on spend on such a ridiculous project, it just goes to prove my point.

Update 2:

Astromajor

What you said makes no sense. Why would water at 80 degrees start forming crystals as soon as water at 35 degrees? You imply that they realize they are being put into a freezer, so they decide to start lining up. Crystallization is triggered at a certain temperature and the hot water has a lot more heat to lose to reach that temperature.

Update 3:

Astro

Throwing a bunch of big words around does not make you right.

Have you actually studied thermo? It is required for Mechanical Engineering. I doubt that it is required for Astro-whatever degree.

If you are looking at the quantum level, then you can't see the forest for the trees and there is no way that I can help you.

Except this. Go to the ME department on your campus and tell the thermo instructor your little theory. He will get a great laugh out of it. (I double dog dare you, now you can not refuse!)

Update 4:

Also, you misspelled Schrödinger equation in all your posing and blustering.

Update 5:

Ok, I get it now, I peeked in your profile.

You ARE a high school science teacher. LOL. No wonder all the blah blah blah big words saying absolutely nothing.

Sorry, thought I was talking to someone with more than a teaching certificate.

Never mind.

Update 6:

PS - You never answered my real question, which was "Do you guys have a newsletter?"

3 Answers

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  • Anonymous
    1 decade ago
    Favorite Answer

    So you're right and wrong. First let's talk about what ice is: the solid form of a water. H2O is a little tricky because it has a very specific structure it needs to form into to transition from liquid to solid (one of the reasons why Ice actually expands when it freezes, something very few other molecules do).

    Because it needs to be in a very-specific crystalline structure, it takes time for the molecules to arrange themselves. Warm water means that the average water molecules have more kinetic energy...they zip along at a faster rate. Cold water means less kinetic energy, or are, on average, slower moving.

    That is why warm water forms ice faster: the molecules can arrange themselves in the crystal structure faster because the molecules are moving faster. Whereas cold water will take a bit longer because they don't get to their "destination" as fast.

    However, it's not like boiling water will freeze faster than ice cold water, not at all. I'm talking about water that's at like...room temperature compared to cold tap water, and even then it's not that significant, so you are right in one sense. But it is true that water that is warm will freeze faster than water that is slightly cold.

    I hope that helps!

    -------

    Boy...did you even read my post? Fine, let's talk quantum levels. The quantum states of higher energy particles have an intuitively increased entropy level as those with lower states. Solids, as you should know based on you "thermodynamic knowledge" require arrangements of particular quantum energy levels to for covalent and ionic bonds. Higher energy particles (warmer water) has an increased probability of quantum states in the required energy, e. This is easily derived from Schroedinger's equation.

    So it makes perfect sense that warm (not hot) water's increased probability of maintaining quantum states (and spin) will form solidified crystals faster than colder water where the probability, g, is slightly less. And again, I'm not talking about extreme conditions where.

    And frankly it's laughable that someone who claims to be the"ones that study thermodynamics" doesn't understand or realize this. You're in the wrong line of work.

  • Anonymous
    1 decade ago

    The Mpemba effect happens MORE than occasionally- in my A Level year I did a whole experiment on the Mpemba effect and I found that the hot water always froze faster except for the cold samples that were at extremely low temperatures (e.g. 3 degrees).

    I think you are the one who is misinformed! Wasted electricity? That's a bit silly. How old are you?

    Source(s): I did these experiments for a whole year!
  • Anonymous
    1 decade ago

    It is hot water that freezes first heres some info

    http://library.thinkquest.org/C008537/cool/freeze/...

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