Why does boiling water freeze faster than room-temp water?
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It doesn’t? Boiling water doesn’t freeze. Room temperature water only freezes if the room is 32 F or colder. I think we need some more details to answer the question you are trying to ask.
It’s called the [Mpemba effect](https://en.wikipedia.org/wiki/Mpemba_effect), and nobody knows how or why it works.
It shouldn’t. Its requires more energy to be removed from the boiling to get it to freeze than room temp water. If you are referring to the videos where people are throwing boiling water into the air when it is freezing outside, this is an evaporative cooling thing since you are exposing the hot water to a huge surface area of cold air and the process of evaporating removes a massive amount of thermal energy which rapidly cools the remaining water, but if you just have 2 cups, one at 212, one at 70 and put them in a freeze, the 70 freezes first.
This is very dependent on conditions.
If you pour out boiling water on a cold surface, some of it will evaporate and the rest will spread out more thinly than the same volume of colder water, so you have more thermal contact with less water and it can freeze faster.
If you put a cup in a freezer, the hot water has more heat to lose, so it will take longer to freeze.
You’re slightly misled on this one. Boiling water (212 Freedom) can’t possibly reach 32 freedom faster than room temperature. Think how that race would look, it’s not even close.
In actuality, BOILED water which had been allowed to cool back to room temperature, will freeze faster than regular room temp water. The boiling removes impurities and whatnots, what’s left will freeze faster than the tap.
This was an encyclopedia and my step dad said it wasn’t true so we took the kettle and boiled some water and filled two ice cube trays. One ice cube tray was filled with cold tap water. And the other with very hot water. We place both in the freezer and checked every 15 minutes. The one that had the boiling water froze first. I’m thinking that the ice cube tray might have cooled down the water to the point where this effect had the best conditions to take place.
It doesn’t mostly. Basically under very specific (so specific that it is rarely replicated with the same setup) it does happen.
Temperature is, is how fast it vibrates. So a room temperature water vibrates slower than hot tap water. So ice being water vibrates even slower than room temperature water. Now if you put room temperature water into a freezer it will cool down and form ice by slowly vibrating less and less. If you have hot tap water it must cool down to room temperature AND then do the same as the room temperature water slowly vibrating less and less. So of course hot liquids DO NOT freeze quicker than room temperature ones. Mostly 🙂
Cooling between two things is very well described in physics. Containers can be multiple materials and surfaces areas with those materials calculating things can get really intricate but all of the maths relys on the average temperature in both materials. Which works well for everything we seems to calculate apart from this one effect that no one understands 😀
It is known as the Mpemba effect after its “discoverer”. Literally no one knows why it happens even him.
The story behind it is all described [here](https://en.wikipedia.org/wiki/Erasto_B._Mpemba). Our physics is pretty bloody good but this is a definite effect so something must be happening in a manner we don’t check.
I have a theory but have no empircal evidence (of course) if you (or anyone else) want a laugh. For ever material (from gold to air) has a value for how fast it transfers heat (ie its thermal conductivity). The value however differs based upon the state too. Water is 0.54 W/m2/C while ice is 2.22 W/m2/C and air is 0.023 W/m2/C (how you’d measure steam i don’t know it would be nightmare). As i stated earlier our working method for calculating cooling use average information because we cannot monitor all the molecules involved. There is cycling of compartively hot and cold parts of liquid as well as the air when they are exchanging heat. These currents of hot and cold create eddies given the right circumstance. Those currents are more pronounced in hotter liquids because they are hotter. I believe these little currents are allowing phase change to occur in isolated molecules but when they get trapped in this increased thermal conductivity state due to an eddie and it “snowballs”. Thermal conductivity uses surface area and if that area increases its going to cool more, faster. This logically could accelerate total cooling and so bypass a cooler drink being frozen. I’m sure someone with a decent physic simulation could attempt to model the fluid dynamics of the beaker and heat exchange if they wanted to but it would be a mammoth undertaking resource wise and frankly its not that important so it will likely stay a mystery.
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