Just googled the subject, and found this one pretty funny...
(From a metric point of view of course, as i am certain there´s plenty who finds it very easy, when raised with the imperial system.)
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I'll have to go along with that one Jan. But then I did start off with Metric being hands down the best for scientific endeavors!
But to answer the question in a more specific manner ... it takes 1 BTU (British Thermal Unit) of heat to raise one pound of water by one degree Fahrenheit at STP.