Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!mnetor!seismo!rochester!kodak!ornitz From: ornitz@kodak.UUCP (barry ornitz) Newsgroups: sci.misc Subject: Re: Common Household Liquid Without Hydrogen (Glass really is a liquid) Message-ID: <662@kodak.UUCP> Date: Sun, 11-Jan-87 00:44:43 EST Article-I.D.: kodak.662 Posted: Sun Jan 11 00:44:43 1987 Date-Received: Sun, 11-Jan-87 06:35:46 EST References: <2630@udenva.UUCP> <2339@eagle.ukc.ac.uk> <3255@milano.UUCP> <2645@ihlpa.UUCP> <3269@milano.UUCP> <2668@ihlpa.UUCP> Reply-To: ornitz@kodak.UUCP (barry ornitz) Organization: Eastman Kodak Co, Rochester, NY Lines: 76 Keywords: Glass, Viscocity, Hydrogen, Solids, Crystalline Structure Summary: Glass as a liquid and viscocity of glass. >From: gadfly@ihlpa.UUCP (Gadfly) >> While glass is amorphous and has some fluid and colloid properties, >> it is not a liquid. >I promise never to try to be helpful about old net ramblings again. >I tried to summarize this thing so it could meet a merciful end, and >what happens? (1) I get mail about not phrasing the question correctly, >(2) I get mail about forgetting the *real* answer--Freon. I suspect >that the question expected the answer "glass" since these folk quizzes >tend to be very superficial, and it's common folk knowledge (the truth is another matter) that glass is a liquid. >ken perlow Sorry to disappoint you Ken, but glasses really are super-cooled liquids. The reason lies in the lack of the activation energy found in crystalline materials. I really do not wish to bore the net with statistical thermo- dynamics and the like, so I will instead quote from "Nature and Properties of Engineering Materials" by Zbigniew D. Jastrzebski (Finally a name more difficult than mine :-] ), John Wiley & Sons, NY, 1959. X-Ray analyses show that the relative positions of atoms in glasses are similar to those of liquids. This means that there exists among the atoms a short-range order, but also a long-range disorder. Hence glasses are generally regarded as supercooled liquids which are unstable with respect to their crystalline phases. ... glasses do not possess definite melting points but soften gradually over a wide range of temperatures. Glass on cooling from its molten state shows an increase in viscocity, thus becoming more and more viscous as the temperature decreases. On further cooling, however, a temperature range is reached at which the glass undergoes a rather sharp change from a viscous to a hard and brittle material. [Note, he did not say solid.] The range of temperature at which this change occurs is called the glass transistion temperature, T sub g, which is often referred to as a second order transition. Below the glass transition temperature the structure of glass is effectively "frozen," but for the most part, it retains the characteristic structure of a liquid. This book also presents several graphs showing the viscocity of glass. These graphs were taken from several references such as: Corning Glass Works, "Properties of Selected Commercial Glasses"; Morey, "The Properties of Glass"; and Jones, "Glass." At room temperature, ordinary glass shows a viscocity of about 10 to the 20th poises. Water for comparison shows a viscocity of about 0.01 poise at the same temperature. This shows that while glass is not a solid at room temperature, it is a lot thicker than molasses on a cold winter morning. :-) To answer several other questions about glass, hydrogen should be present in only negligible amounts in glass since any hydrogen present in molten glass would be oxidized by the oxides present to form steam which would vaporize off. Glass is made in an oxidizing atmosphere as opposed to most metals and alloys which can contain considerable dissolved hydrogen. Also, the mirrors in most large reflecting telescopes use fuzed silica rather than soda-lime glass. This material shows a more crystalline structure than ordinary glass; it is similar to that of quartz (a three dimensional network of silicon atoms bonded through oxygen links) with the exception that the bond angles are not constant, causing an irregular arrangement of atoms. Colloids can be arbitrarily defined as matter is a fine state of subdivision, larger than atomic and simple molecular dimensions, but smaller than particles visible to the naked eye. Glass by itself would not qualify, but ruby glass with colloidal particles of gold dispersed in the glass might. I hope this treatise will end the discussion on hydrogen-less liquids about the house. Glass, freon (at least the varieties most commonly used in household refrigeration units) and carbon tetrachloride are equally correct answers. Let's find some new controversy to argue over, this one has been around for over six months! Only this time, we should find a subject where computer science types have a fair chance of understanding the physics. :-) Oops! Sorry about that, folks. I can hear the mob beating on the door! Barry L. Ornitz Eastman Chemicals Division Research Kingsport, TN