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Amorphous Solids
- particles are randomly arranged and have no ordered long-range structure
- Example: rubber
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Crystalline Solids
- particles have an ordered arrangment extending over a long range
- - ionic, molecular, covalent network, metallic
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Ionic Solids
- particles are ions ordered in a regular three dimensional arrangement and held together by ionic bonds
- Ex: NaCl
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Molecular Solids
- particles are moelcuels held together by intermolecular forces
- Ex: ice
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Covalent Network SOlids
- particles are atoms linked together by covalent bonds into a giant 3D array
- Ex: quartz
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Metallic Solids
particles are metal atoms whose crystals have metallic properties such as electricalconductivity
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Interference
occurs when two waves pass through the same region of space
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Constructive interference
occurs if the waves are in-phase, producing a wave with icnresaed intensity
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Destructive Interference
occurs if hte waves are out-of-phase, resulting in cancellation
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Diffraction
occurs when electromagnetic radiation is scattered by an object containing regularly spaced lines (like diffraction grating) or points (like atoms in a crystal)
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Coordination number of:
body centered cubic
8
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Coordination number of:
simple cubic
6
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Coordination number of:
hexagonal and cubic closest-packing
12
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Which packing takes up the most space?
hexagonal and cubic
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unit cell
a small repeating unit that makes up a crystal
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ionic crystals characteristics
- charged species
- generally hard/ brittle nad high melting point
- conduct ONLY as melt or in a solution
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Molecular Crystal characteristics
- held together by intermolecular forces
- soft and low melting point
- nonconducting
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Covalent (NEtwork) Crystals
- held together by covalent bonds
- generally hard and high melting
- nonconducting
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Allotropes
- different structural forms of an element
- Carbon: graphite, diamond, fullerence, nanotubes
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__ is a molecular solid whose molecules have hte shape of a soccer ball with twelve pentagonal and twenty hexagonal faces and each carbon aton in sp2 hybridized
fullerene
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__ consist of sheets of graphite rolled into tubes of 2-30 nm diameter.
carbon nanotubes
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Metallic Crystals:
Characteristics.
- BCC, FCC, or Hex arrangement
- Positive ions in a "sea" of electrons
- Variable hardness and melting point
- All conduct
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A __ is a graphical display of the temperatures and pressures at which two phases of a substance are in equilibrium.
phase diagram
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Triple Point
the only condition under which all three phases can be in equilbrium with one another
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Critical Temperature
the temperature above which the gas phase cannot be made to liquefy at any pressure
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Critical Pressure
the minimum pressure required to liquify a gas at its critical temp
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Supercritical Fluid
a state of matter beyond the critical point that is neither liquid nor gas
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