chapter9GREG - Chapter9 SolidsandFluids StatesofMatter...

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Chapter 9 Solids and Fluids
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States of Matter  Solid Liquid Gas Plasma ---this is  total BS . Liquids and gases  are not always distinguishable. What  defines a state of matter is its symmetry  more than any other one thing.
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Crystalline Solid Atoms order in a lattice (beautiful, no?) Faceting is a  sign of  microscopic  order Diamond
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Amorphous Solid Atoms are arranged  almost randomly, but  rigid if you push on it! Examples include glass  (SiO2) We don’t understand  glasses still,  random=difficult  in this  case
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More About Solids External forces can be applied to the  solid and compress the material When the force is removed, the solid  returns to its original shape and size This property is called  elasticity Generally we refer to a ‘rigidity’ to external  forces.
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Liquid Has a definite volume, No definite shape The molecules “wander” through the liquid in a  random  fashion The intermolecular forces are not strong enough to keep  the molecules in a fixed position A liquid is not ‘rigid’ to an external stress and the ‘random’  distribution of molecular position means it looks isotropic  from all directions. In a solid the symmetry is lower,  because there are definite crystal axes (it’s ‘lost’ rotational  symmetry). 
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Gas Has no definite volume, Has no definite shape.  What the book means here is that a gas can be  compressed, but water is mostly incompressable  (except at very high pressure). Molecules are in constant random motion Average distance between molecules is large  compared to the size of the molecules. This is the  major difference between a liquid and a gas.  They’re both ‘isotropic’ though.
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Mesophases Imagine now being crystalline in  one direction, but isotropic in the  plane perpendicular to it. This is  (one form of) a liquid crystal (=flat  screens).  Some rotational symmetry was lost. It is rigid to a force in one direction,  soft and squishy like water in  another Squishy this  way Rigid
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What ‘condensed matter’ physicists think  about phases really (magnetic example) A) The spins point randomly, like the  random positions of molecules in a  liquid, and the material appears  isotropic B)-E) the spins are no longer random, but form one of a ‘zoo’ of magnetic orders  which ‘break’ the isotropic symmetry  to something with an axis.  ‘phase’ of matter, usually means a  different symmetry Modern ideas are challenging this  with other geometric ideas (topology)
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Types of Matter Normal matter (‘baryonic’) About 5% of total matter, made up of the particles 
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This note was uploaded on 05/17/2011 for the course PHY 2053 taught by Professor Buchler during the Spring '06 term at University of Florida.

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chapter9GREG - Chapter9 SolidsandFluids StatesofMatter...

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