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| Freezing Speed of Hot Versus Cold Water |
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| Nominal Animal:
I completely forgot, and I've actually done it in real life! :palm: Here is Viva Frei doing it on Youtube: |
| IanB:
That's a cool video, but it doesn't break any laws of physics. Calling it the "Mpemba effect" is just a clickbaity title to get views. |
| bdunham7:
--- Quote from: IanB on February 23, 2022, 01:59:05 am ---That's a cool video, but it doesn't break any laws of physics. Calling it the "Mpemba effect" is just a clickbaity title to get views. --- End quote --- This is why snow machines use hot water...oh, wait... |
| Nominal Animal:
--- Quote from: IanB on February 23, 2022, 01:59:05 am ---That's a cool video, but it doesn't break any laws of physics. --- End quote --- Neither does the effect discussed, even if you believe otherwise. Next time you are somewhere cold enough, do the same with both hot and cold water. Then come back and say that your results have nothing to do with the effect discussed here, even though only the hot water turned to ice mist, and the cold water remained as liquid droplets. --- Quote from: bdunham7 on February 23, 2022, 02:23:37 am ---This is why snow machines use hot water...oh, wait... --- End quote --- Ha, ha. Forgot about total energy? You know, the electricity or fuel you pay for when using snow machines? That was a pretty dumb post from you, I must say. This thread is making me really depressed, to be honest. So much "I don't believe you, because it is not how I believe things to be", instead of just checking out the peer-reviewd articles and studies by actual chemists and physicists. Just "Because I cannot believe you, you must be wrong" type of arguments, and references to people who constructed a test setup where the phenomenon does not occur, and assume that must mean that the phenomenon does not exist. No true counterarguments, just throwaway claims of "this violates that", without any basis for such claims beliefs. None of this violates any of thermodynamics or anything else; I've even explained the most likely mechanism exactly how and why this happens above (with links to the underlying articles that supports that argument). Do you not realize when your arguments are not science, but religion? Dammit, I'm out. |
| TMM:
If you control everything other than the temperature of the water then once the water reaches the same temperature as the cold water, it can only take the same amount of time as the cold water to freeze. Claiming otherwise is claiming that the water has a memory effect. Of course in practice it's very difficult to control every variable other than the water temperature as the temperature of the vessel and surrounding air will not be the same after chilling the hot water to a cool temperature, as compared to the cool water's initial starting point. The hot water vessel and surrounding air are likely to be much cooler when the water contained reaches the 'cool' temperature and is continued to be chilled, as compared to the vessel that starts off with 'cool' water and just begins to be chilled. If the vessel and surround air are already cooler when the 'hot' water reaches the 'cool' temperature, then you'll be extracting heat from it at a faster rate than the cool water vessel that you have just begun chilling. Of course, you've wasted all the time/energy chilling it from hot to cool, so it can't possibly get to freezing faster than the cool water if you start chilling them at the same time. The time taken to get from hot to cool may be negligible compared to getting from cool to freezing, therefore any variance caused by not controlling all test variables perfectly may well let the 'hot' water freeze first for some test samples but if you do enough trials the average time to freeze should be slower for the hot water. This is basically the same as claiming that a capacitor initially charged to 100V will discharge to 1V faster than one initially charged to 20V when you put the same value resistor across them. When the 100V capacitor has discharged to 20V it is in the same initial state as the 20V capacitor, therefore it can only take the exact same amount of time to go from 20V to 1V. The time taken to get from 20V to 1V is twice as long as from 100V to 20V so if test variables are poorly controlled (such as the value of the capacitor and resistor) it is possible for one capacitor initially charged to 100V to discharge to 1V faster than another capacitor initially charged to 20V... |
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