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Which boils faster, hot or cold water?
The hotter something is, the more energy it craves to heat it further.
This one may be surprising though.
Now you got me confused Geezer?
Quote from: yor_on on 07/04/2011 10:30:42Now you got me confused Geezer? Sorry Yoron  Maybe it's a terminology thing.What I mean is that it always takes the same amount of energy to raise the temperature by a certain amount. The specific heat of a substance is its thermal energy capacity per unit mass. So, I would say its "craving" for heat is constant regardless of its temperature.(Although it looks like Lightarrow will point out that is not always the case.)
There's also heat transfer to take into account. In theory, the hotter the water is, the less efficient your burner will be at actually transferring energy to it, since heat transfer is generally more efficient for larger temperature differences.
Ok, so, if you have cold water at 1°C and you put it in a pot on the flame, it will take less time to heat it to 41°C then the time required to heat hot water at 41°C from 41°C to 81°C.But if you want to boil the cold water, you still have to reach 41°C, then you have to take it from 41°C to 100°C, so the time required to boil cold water will always, obviously, be greater then the time required to boil hot water...