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From: rep@panda.UUCP (Pete Peterson)
Newsgroups: net.cooks
Subject: Re: Why boil cold water
Message-ID: <502@panda.UUCP>
Date: Mon, 13-May-85 08:04:47 EDT
Article-I.D.: panda.502
Posted: Mon May 13 08:04:47 1985
Date-Received: Thu, 16-May-85 03:42:03 EDT
References: <707@dedalus.UUCP> <7285@Glacier.ARPA>
Reply-To: rep@panda.UUCP (Pete Peterson)
Organization: GenRad, Inc., Concord, Mass.
Lines: 55


In article <7285@Glacier.ARPA> reid@Glacier.ARPA (Brian Reid) writes:
>>      There is actually a scientific reason to boil cold water as opposed to
>> hot (it may not be the pertinent reason, though).  Cold water will boil
>> FASTER (yep, that's right) than hot water.  This is because the cold water
>> contains more oxygen than the hot water (now what that does is beyond me).
>> The above strange fact was passed on to the freshman chemistry class I took
>> in college.
>
>I remain deeply skeptical. So much so, in fact, that I went in to my kitchen
>just now and did an actual experiment. (details of experiment at end of
>message for those who care). 
>----------------------------------------------------------------------------
>	     Initial  Time to   Kilojoules   joules/ <-- you can think of
>	      temp     boil      absorbed    second    this number as the
>Hot water     60F      204sec      184        901     "boiling efficiency"
>Cold water   135F      365sec      347        950
>----------------------------------------------------------------------------
>
>The summary result is that hot water boils faster than cold water, as one
>might have expected. A joule/second is a watt, so what this means is that my
>1200-watt burner was delivering 901 watts to the hot water and 950 watts to
>the cold water. The probable explanation for this is that the energy
>transfer rate levels off sharply as the water approaches boiling, because of
>evaporative loss, and that the cold water stays in the high-efficiency range
>for a larger percentage of the total time. Another way of looking at these
>numbers is that not only does hot water not boil faster than cold water, it
>actually takes LONGER, degree for degree, than cold water (by about half a
>percent).
>
Am I confused or do the first and last parts of this paragraph say opposite
things about which boils faster?

>The experiment: cold water boil: run cold tap water for 2 minutes into pan;
>empty pan and quickly measure in one liter of cold tap water. Let stand for
>60 seconds (to equalize temperature of water and pan), then measure
>temperature and place on preheated electric stove burner. Hot water boil:
>the same, but use hot tap water. Alternate cold, hot, cold, etc. three
>times, for a total of six measurements, allowing the burner to reheat for
>1 minute in between measurements.
>
>The pan was a copper saucepan (lined with nickel) that weighs 616 grams. The
>specific heat of copper is 0.0949, which means that the pan's heat
>absorbtion was 5.8% of the water's (mass of nickel assumed to be negligible;
>specific heat of Nickel is 0.1035)
>-- 
>	Brian Reid	decwrl!glacier!reid
>	Stanford	reid@SU-Glacier.ARPA


It appears that Brian's results agree with the counter-intuitive statement
of the original article; the APPARENT disagreement results from an unusual
use of the terms "hot" and "cold".

		Pete Peterson