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## Block of Ice

Science brain teasers require understanding of the physical or biological world and the laws that govern it.

 Puzzle ID: #26973 Fun: (2.83) Difficulty: (2.16) Category: Science Submitted By: phrebh Corrected By: phrebh

Warbucks and Swig were arguing about the best way to melt ice when Fred walked up.

Warbucks was saying, "That's ridiculous, the best way to melt a block of ice is to put it in the oven."

To which Swig replied, "Nonsense, boiling water is the way to go. You drop the block into a pot of boiling water and it will melt much quicker than in the oven."

"Listen," Warbucks averred, "even an oven set to only 200 degrees Fahrenheit, the block would melt faster than in your boiling water."

Seeing that Fred had approached, and knowing Fred's penchant for all things esoteric, Swig asked him to intervene. Swig told Fred that he thought that the fastest way to melt a block of ice, without breaking it up first, would be to drop it in boiling water. He also told Fred that Warbucks insisted that a warm oven would be the fastest method. He then asked Fred which of them was right.

Fred simply replied, "why, neither of you, of course."

What is the fastest way to melt a block of ice without first breaking it up into smaller pieces?

Fred went on, "the fastest way to melt a solid block of ice is to put it in a bowl in the sink and run hot water into the bowl. It's all to do with convection and thermal transfer. The hot water, being closer to the temperature of the ice than boiling water, will more quickly dispense heat into the block. Couple that with the convection caused by the fact that the water is constantly moving while being replenished and you have ideal conditions for the transfer of heat necessary to melt the block."

"They both suffer from a similar problem," Fred answered. "The boiling water does have a certain amount of convection, but because the water is so hot, the transfer of heat actually works to cool it down more than to heat up the ice. The oven is even worse because of the complete absence of external convection. All the block is doing is keeping your oven cool, which actually makes it the slowest way to melt a block ice short of leaving it in the freezer. Even running cool water over the ice in the bowl will melt it more quickly than using an oven or boiling water."

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