the nature of solids chapter 10. solids: gases = very free to move liquids = relatively free to move...
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The Nature of Solids
Chapter 10
Solids:
• Gases = very free to move
• Liquids = relatively free to move
• Solids = not very free to move
Solids:
• Solids do not move freely like liquids and gases
• Rather, they vibrate about fixed points
Solids:
• Do not take the shape or volume of the container
• They are dense and incompressible
Solids and kinetic energy:
• Increase in average kinetic energy = increase in particle vibration = increase in temperature
Melting Point:
• Mp = Solid turning to liquid
• Vibrations are strong enough to overcome the intermolecular interactions
Freezing Point:
• Opposite of melting point
• Liquid turns into a solid because the particles slow down and intermolecular forces are stronger
Equilibrium:
• A solid will melt and freeze at the same temperature
• This is the point of equilibrium, assuming temperature is remaining constant
Solids:
• Ionic Solids (ex: NaCl) = high melting points
• They have relatively strong forces holding them together
This is table salt
Solids:
• Molecular compounds = low melting temperatures
• Example – hydrogen chloride has a melting temperature of -112 0C
Solids:
• Not all solids melt, some will decompose
• Example: wood, cane sugar
Sugar or RockCandy
MMMMMM
Crystal structure:
• Crystalline (crystals) = atoms, ions or molecules are arranged in a repeated, three dimensional pattern called a crystal lattice
Crystals:
DiamondStructure
Crystals:• Have regular shape• Shape reflects the arrangement
of the particles within the solid• Types of bonds determines the
melting point• Ionic = high melting point• Molecular = low melting point
Graphite Structure
Crystals:
• Have sides or faces
• Angles of the sides for a given crystal are always the same
Crystal Classification:
• Galena–Cubic
Crystal Classification:
• Zircon–Tetragonal
Crystal Classification:
• Blue Topaz–Orthorhombic
Crystal Classification:
• Gypsum–Monoclinic
Crystal Classification:
• Amazonite–Triclinic
Crystal Classification:
• Tourmaline–Hexagonal
Crystal Classification:
• Calcite–Rhombohedral
Shape of Crystals:
• Shape depends on arrangement of crystals
• Unit cell = smallest group of particles that retains geometric shape
More than one Form?
• Carbon is an example of a crystal that can exist in more than one form
Many forms of carbon:
• Diamonds• Graphite• Buckyball or
Buckminsterfullerene- 60 + carbon atoms shaped like a soccer ball
Many forms of Carbon:
• Allotropes–Two or more molecular forms of
the same element in the same physical state (diamond, graphite & buckyballs)
Example: diamonds and graphite
Amorphous Solids:
• Lack ordered internal structure• Non- crystalline• Example- rubber, plastics,
asphalt and glasses–Glasses are sometimes called
super cooled liquids
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