I know that hot water freezes faster, so does cold water boil faster?

Answer 1

Well, you shouldn't say that you know that hot water freezes faster than cold. I can state with great certainty that you can conduct experiements over and over and the cold water will always freeze first. I have checked this supposed phenomenon myself by putting hot and cold water outside during the Winter. No surprisingly the cold water temperature was always below that of the initially hot water.

The "Mpemba Effect" is mostly just an urban legend. People like the story because it's about a boy in a poor country who was ridiculed by his teacher for having different ideas. Supposedly, they were making ice cream with boiled milk and they were supposed to let it cool down before putting it in the freezer. But, he didn't and his froze first.Then supposedly he was later vindicated when a university professor conducted experiments and found out he was right. Great story.

Of course, I've never boiled milk when making ice cream. In fact, I've never heated the milk up at all. The story sounds a bit bizzarre because normally to make ice cream you have to use a dasher to mix air in as it freezes. Apparently, third world ice cream is different and would be simply a frozen chunk of milk.

The problem with the vindication of this ridiculed boy is that the professor doing the experiments did them in 1969 and this has never been duplicated in the 37 years since. Someone was able to demonstrate that you could get 195 degree water to freeze before 150 water under certain circumstances. However, these conditions would be nothing like Mpemba's account.

If you do a search on Google for information about this effect you will find that the last actual research on this was in 1995 and 1996 and their experiments only showed that you could have differences under some circumstances due to dissolved gases and supercooling. Yet, still no one has duplicated Mpemba's supposed effect.

Supercooling is not a valid answer because things don't freeze at the same temperature when they are supercooled. I once had this trip me up during a chemistry experiment when I got supercooling but no one else in the class did. Also, on MythBusters they had a very nice demonstration of how distilled water can be heated in a microwave higher than the boiling point without boiling. Then as soon as it is disturbed it practically explodes in a shower hot water and steam.

So, you could similarly claim that tap water boils faster than distilled water however this would in fact but just as incorrect as saying that "hot water freezes faster than cold". Finally, in spite of the nonsense annocdotes listed about ice cream makers people have been making commercial ice in vast quantities for quite some time. None of the commercial ice makers have ever used hot water to make ice faster.

Answer 2

The statement that hot water freezes faster than cold water is not accurate. Water that has been heated will lose some or all of the dissolved CO2 that is solution with the water. This makes the water freeze at a slightly higher temperature than water that has some dissolved CO2 in it. Changing the freezing point of water by adding small amounts of contaminants is known as freezing point depression. So yes, water that has been heated and cooled to near the freezing point will freeze faster, because it doesn't have to get as cold as water with dissolved CO.

But if you are talking about pure water only, and an equal rate of heat input, cold water will not boil sooner than hot water.

Answer 3

Nope.

Hot water freezes faster because of the density properties (The curve of how far the atoms are apart verses temperature) of water. It gets more dense as it gets cold, then less dense when it freezes. By trying to take it from a hot state to a very cold one the atoms give up their energy more easily because they are already in the same density state they will be in frozen.

When boiling, it is simply a mater or adding heat. For the same heat input and the amount of water, colder water takes longer to boil.

Answer 4

Hot water boils faster than cold water.
Cold water changes temperature faster than hot water on a graduated curve until, get this, it becomes hot. There is no way to boil water without it becoming hot first, thus it will take longer to boil cold water simply because of heat transfer.

Answer 5

Come on some of you!
Use those brains.
Put some hot water in ice cube trays and cold water
in others. Put in freezer. Check frequently.

You'll notice something odd happens. The hot water turns
cold before freezing! Meanwhile, the cold water has frozen!
Think!!!!!!
Boil some cold water. It turns hot first, then boils!
Hot water put to boil doesn't go through that extra step.

Answer 6

You are confused. Hot water does not freeze faster. Temperature changes happen at a rate directly proportional to an objects surroundings...water is no diferent. Cold water, which is closer to the freezing point, will require a much smaller change in temperature to reach freezing.

Answer 7

Hot water does not freeze faster... that's a myth

Answer 8

Hot water will boil faster because it takes less BTU'S to get it to 212 f.

Answer 9

I've actually heard that - something to do with the amount of air in the cold water...

And for those of you calling this guy stupid, look up the Mpemba Effect, its a real thing.

Answer 10

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