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From: roy@gitpyr.UUCP (Roy J. Mongiovi)
Newsgroups: net.cooks
Subject: Re: boiling cold water
Message-ID: <401@gitpyr.UUCP>
Date: Thu, 16-May-85 09:13:21 EDT
Article-I.D.: gitpyr.401
Posted: Thu May 16 09:13:21 1985
Date-Received: Fri, 17-May-85 04:57:07 EDT
References: <3707@alice.UUCP>
Organization: Georgia Institute of Technology, Atlanta, GA
Lines: 36

> Scientific American covered this subject a few years ago,
> noting that that it necessarily took more heat to
> freeze hot water, but that hot water made some refrigerators
> turn on sooner, thus speeding the freezing process.

That sounds quite reasonable to me.

> In the second, I WEIGHED my old water heater when I got rid of it
> and it weighed several pounds more than its original shipping weight...
> That more or less proves that over its lifetime, it had minerals
> precipitated > OUT into it, thus leaving less total minearl content
> in the hot water.

Actually, all that proves is that more minerals entered the tank than
left it.  It says nothing about the mineral content of cold water.  I
know that in my apartment complex the hot water has considerably more
rust than the cold.  If I make macaroni starting with hot water I get
orange macaroni....

> In the third, practiced after lunch with a microwave oven,
> hot water boiled much faster than cold water.

Well, I think this really depends on your definition of boiling.
Remember chemistry lab, when you put boiling chips in the liquid
to speed up boiling and to prevent the solution from exploding?
I think the dissolved oxygen in cold water has an effect like that.
As you raise the temperature of water it can dissolve less oxygen,
and the O2 starts to bubble out, thus aiding the start of boiling.
I don't think there is any question that it takes longer to get
cold water to 100c than hot water, but it might take less time
for cold water to start to bubble.  A microwave heats differently,
and this may have masked that result.
-- 
Roy J. Mongiovi.	Office of Computing Services.		User Services.
Georgia Institute of Technology.	Atlanta GA  30332.	(404) 894-6163
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