Does Hot Water Freeze Faster Than Cold Water?

Does hot water freeze faster than cold water? Turns out, the answer to this question is a lot trickier than it seems!

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[abhisheksanandreas]

Does that mean cold water will boil faster than hot water **angry Gordon Ramsey noises**..

[therealstubot]

My grandfather told me this back in the 1970's. He said his first car didn't have any anti-freeze, so he used to drain the water when it was cold, and refill it when he needed to go somewhere. He also said that if you put the hot water back in the engine, it would freeze faster than putting cold water in. This made no sense to me, and I was probably 9 or 10 years old when he shared this with me. Being a scientific type, I did not believe him. My grandmother and I spent a day just heating and freezing samples of tap water to test his claim. Our results were inconclusive. Completely random results. Sometimes the boiling water would freeze a minute before the 40 degree F water. Sometimes the cold water would freeze first. I learned a lot about variables and rigor from my grandmother that day, but I also learned that my grandfather wasn't necessarily full of crap.

[SPAJ]

Normally the science news goes something like "here's something new we discovered and you need to know about it because it's cool". This one is more "we don't know, that's interesting too, give this a whack if you're feeling curious". I love it!

[pkeros]

"Aristotle said the same thing in the year 4 BCE"

*raises eyebrow, checks Wikipedia*
Aristotle: Born 384 BC, Died 322 BC.

Perhaps a different Aristotle that the one we all know and love?

[piranha]

I'll probably be trying this in my lab next weekend with our ultra-pure water and some sealed containers. I'll keep you posted!

[cosi]

What is that grumming sound in your ears that occurs sometimes if you yawn and close your eyes real tight??

[sirMAXX]

Exactly. Impurities is what I was just thinking, raising, or lowering the freezing point, depending what the impurities are. Seems to make a lot of sense.

[ryanlandry]

Rate of evaporation is very important to consider because it's transferring thermal energy. Cold air is also dryer then warm air, so there's going to be very rapid evaporation and temperature change with hotter water. I suspect water freezes on top first because there's a greater thermal transfer with evaporation taking place. It's how we cool our bodies with sweat and why we can't cool ourselves well in a humid environment. Cold dry air cools us immediately as you can see the water vapor coming off you body when it's cold enough outside.

Side note: When I use denatured alcohol to clean my 3D resin prints I wave my hands in the air to dry the alcohol off my gloves quickly and my gloves get very cold since alcohol evaporates rapidly. It's an interesting effect. 👍

[DefinedEdits]

"maybe youll get an effect named after you" lmaoo

[videogyar]

But what if a superior alien race comes to Earth and says: humans you have the chance to get into our galactical empire with unlimited knowledge and resources, you just need to prove your intelligence by answering a simple question: Does Hot Water Freeze Faster Than Cold Water?
And we would miss our chance:(

[RavenwolfFoxtrack]

I had always thought it had to do with the loss of energy of excited particles from thermal change, such that excited faster moving particles will expend more energy to stay in the same excited state as their energy is drawn and changed.

[anthonydobbs]

Was it the ghost of Aristotle? He died in the mid 300s bc 4 bc Is like confusing Newton and hawking, s time on earth.

[monhi]

There is a critical point that I think helps regular people understand why this might look possible and why it’s so easy for people to produce conflicting results. It takes significantly less energy to cool water down than it does to actually turn liquid water into ice (aka freeze). So realistically the energy required to freeze hot water and the energy required to freeze cool water are much much closer than people would think intuitively. It makes sense that literally changing matter from one phase to another would take a ton of energy but very easy to overlook unless you start thinking about it lol

[seannot-telling]

I used to work at an ice arena and when we used hot water during the resurface process is always seemed to freeze much faster then the cold and also gave a higher gloss to the surface. The gloss was more likely do to melting the surface ans smoothings things out a little better.

[ionlymadethistoleavecoment]

Not the only one to mention this, but why can't they just use pure water?

[knutearmstrong]

"Who knows, maybe you'll get an effect named after you."

[premier]

they can build the LHC but not figure this out? Imagine the headlines: "Nobel prize for guy who figures out boiling water"

[spencert]

The hot water has to cool to the exact same temperature as the cold water at some point and then somehow surpass it. If both samples of water are the same and in a closed system this makes no sense. whats much more likely to effect it is where you put it in the freezer.

[davidalearmonth]

A pipe froze in my house last winter. It was the Hot water pipe. (and it was in the same basic location as the cold water pipe).

It was a dead line in our house, but it still had pressure to it, it was capped off on the far end.

I was rather surprised, but my plumber said that the hot lines freeze first, based on their experience. Interesting.

[DonaldHolben]

hot water has less dissolved oxygen or air bubbles which aids with a harder surface.I worked at a rink when i was younger, They fill the zamboni up with very hot water before it goes on the rink.