Does hot water freeze faster than cool?

[Llewellyn]

Horse relevance being I keep hearing of people putting warm water in their water buckets hoping it freezes slower. (Nb. this is different to offering your horse warm water )
Now about eight years ago on Gardeners World on Radio 4 a listener did an experiment in his bird bath. He had been putting in warm water hoping it would take longer to freeze but it froze quicker than the cold water because apparently the greater the temperature change the faster ice forms.

Anybody know if this is true?

 

[kerilli]

Yes, hot water freezes faster, it's called the Mpemba effect:

http://en.wikipedia.org/wiki/Mpemba_effect

but, pouring hot water in will melt some of the ice if it's in there, and make the water more palatable so help prevent equine dehydration, so it's still a good idea imho.

 

[skint1]

I did not know that!

 

[La Fiaba]

Even pouring cool water over the ice will melt it as it's warmer than the ice, same principles as de-icing your car, no?

 

[Queenbee]

I love google

'I google, you google, we all google'

http://www.xs4all.nl/~johanw/PhysFAQ/General/hot_water.html

 

[Llewellyn]

I totally agree with doing it so your horse can drink just I was fourteen when I heard it and wondered if I had remembered right, so sad age 14 listening to Gardeners World.

 

[Ranyhyn]

Well well well

 

[T-Bag]

Horse relevance being I keep hearing of people putting warm water in their water buckets hoping it freezes slower. (Nb. this is different to offering your horse warm water )
Now about eight years ago on Gardeners World on Radio 4 a listener did an experiment in his bird bath. He had been putting in warm water hoping it would take longer to freeze but it froze quicker than the cold water because apparently the greater the temperature change the faster ice forms.

Anybody know if this is true?

Not only can it freeze faster, but it more of the water will freeze faster.

 

[posie_honey]

yup its true - search on utube for boiling water bomb

i put luke warm water into the buckets - so it mixes with cold water - and pack the sides with snow - and its not frozen over too much here (in -16 etc not been warmer than -1 for 12 days now ) by morning there's a few layers where you can see they've broken the ice but its always fine for them to drink
in fact - lower down there's not even ice on the inside of the bucket snow def insulates

 

[Honey08]

I'm not sure that I agree with it though. If I put cold water out for the hens (in a tuppaware tub) it is frozen by midday, so I've been putting very hot tap water out, and its stayed liquid much longer... I also put warm water on my windscreen to defrost it, as the cold freezes again instantly. Perhaps that its not quite boiling perhaps?

I put hot water in one of our horse's buckets the other night, on top of the ice, and it must have been warm still. He was disgusted!

 

[Chumsmum]

I've heard that it does too but agree about it being more palatable, in the winter if I leave one 'normal' bucket of water and one that has been topped up from the kettle (so more warm than hot), my horses will always drink the warmer one.