Re: pinhole re: a question on heat

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From: DLPorter (dpotasnik@earthlink.net)
Date: Wed May 15 2002 - 07:10:23 PDT 

Message-ID: <3CE26C4F.A65ACED@earthlink.net>
Date: Wed, 15 May 2002 07:10:23 -0700
From: DLPorter <dpotasnik@earthlink.net>
Subject: Re: pinhole re: a question on heat

Without getting too technical, water is always trying to evaporate. The
higher the temp, the more will evaporate. This water vapor that has
freed itself from the surface of the water exerts a pressure on the
atmosphere, (note how a lid on a pot of boiling water giggles). We call
this vapor pressure. Now, the atmosphere also exerts a pressure, but on
the surface of the water. boiling happens when the vapor pressure
equals the atmospheric pressure. The temp at which these two pressures
are equal is called the boiling point. Different liquids have different
boiling points. Paul Hewitt, in his Conceptual Physics, explains
evaporation and condensation really well and also talks about why
evaporation causes cooling while condensation causes warming.
david porter

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