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From: davis@hplabs.UUCP (Jim Davis)
Newsgroups: net.misc
Subject: Re(1,2,3): boiling hot water(now freezing)
Message-ID: <1706@hplabs.UUCP>
Date: Tue, 16-Aug-83 13:47:55 EDT
Article-I.D.: hplabs.1706
Posted: Tue Aug 16 13:47:55 1983
Date-Received: Wed, 17-Aug-83 20:21:25 EDT
Organization: Hewlett Packard Labs, Palo Alto CA
Lines: 25


	It seemed to be time to throw a few more "facts" into
the confusion over the freezing of water.  First, arguments
that state that hot water freezes first because it loses heat
faster through evaporation are false.  All this does is cause
the hot water to become cold water, which then acts like cold
water and cools slowly.

	However, under some circumstances hot water does freeze
faster than cold.  When hot water is put into the freezer convection
currents are set up which cause the hot water to cool rapidly.
This occurs because of the greater thermal gradient.  These convection
currents do not die out as the water cools.  Hence, the water
continues to cool rapidly.  This phenomenon depends upon the
shape of the container.  Some ice cube trays fit the bill.

	There is a better reason to freeze hot water.  The solubility
of many gasses in water decreases with increasing temperature.
If ice cubes are made from cold water they will not be clear,
while those made from hot water are.
-- 
					Jim Davis (James W Davis)
					...!ucbvax!hplabs!davis
					davis.HP-Labs@UDel-Relay
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