RE: why liquids are incompressible? [bcc][faked-from][bayes]

From: <Bruce>
Date: Mon May 17 2004 - 09:35:00 EDT

An exception to liquids solidifiying under pressure is water. Liquid water molecules are more densely "packed" than they are in ice. When compressed, ice will liquify, as long as the temperature doesn’t also drop. Mercury is similar. Not many other exceptions, but these are important.

                            ... Bruce D. Bullough ...
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-----Original Message-----
From: Christopher Wright [mailto:chrisw@skypoint.com] Sent: Saturday, May 15, 2004 10:58 AM
To: ‡
Subject: Re: [PipingDesign] why liquids are incompressible? [bcc][faked-from][bayes]

>1) Why liquids are incompressible? When gas is compressed it liquifies,
>why liquids on compression don't solidify?(Seems to be a foolish
>question but i want to know the scientific reason behind this.)
Liquids do solidify when the pressure is high enough and the temperature is low enough. Conversely a solid like steel will liquify and vaporise if you get it hot enough.

The scientific reason is that when the temperature is high the molecules of a gas move very fast and overcome the forces that might otherwise hold them together. When the temperature goes down the velocity goes down and the molecules don't bounce around so much and the gas liquifies. That's how you liquify nitrogen, for example. If the temperature goes down even further the molecules tend to cling because their motion can't overcome the attractive forces of nearby molecules. Then the material solidifies.

Liquids are also not incompressible. The don't compress very much, compared to gases, but they do in fact compress.

If you're interested in this find yourself a physics text and read through the part of thermodynamics

Christopher Wright P.E.    |"They couldn't hit an elephant at
chrisw@skypoint.com        | this distance"   (last words of Gen.
___________________________| John Sedgwick, Spotsylvania 1864)

http://www.skypoint.com/~chrisw

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