Chapter 12.2 : Solids

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Chapter 12.2 : Solids

  1. 1. Solids<br />Chapter 12.2<br />Objectives:<br />Describe the motion of particles in solids and the properties of solids according to the kinetic-molecular theory.<br />Distinguish between the two types of solids.<br />Describe the different types of crystal symmetry. Define crystal structure and unit cell.<br />
  2. 2. Properties of Solids and Kinetic-Molecular Theory<br />Particles are more closely packed.<br />Intermolecular forces are much more effective in solids.<br />Hold molecules in fixed position, only vibration movement<br />More ordered than other phases<br />Two types of Solids<br />Crystalline solids:<br />Consist of crystals, which are, a substance in which the particles are arranged in an orderly, geometric, repeating pattern.<br />Amorphous solid:<br />Solids whose particles are arranged randomly<br />Ex: glass and plastic<br />
  3. 3. Definite Shape and Volume<br />Tightly packed particles<br />Very little space for compression<br />Do not flow b/c fixed position of particles <br />Amorphous solids do flow (random arrangement)<br />Definite Melting Point<br /><ul><li>Melting
  4. 4. Physical change of a solid to a liquid by the addition of heat. (Temperature which a solid becomes a liquid)
  5. 5. Kinetic energy of particles overcome attractive forces holding them together.
  6. 6. Supercooled Liquids
  7. 7. Substances that retain certain liquid properties even at temperatures at which they appear to be solid.</li></li></ul><li>High Density and Incompressibility<br />Particles are more closely packed together<br />Why are wood and cork compressible?<br />They are not!!<br />They contain pores filled with air, which is what can be compressed<br />Low Rate of Diffusion<br /><ul><li>Can it happen?
  8. 8. YES, But millions of times slower than liquids and gases</li></li></ul><li>Crystalline Solids<br />Crystal Structure:<br />Total 3-D arrangement of particles is a crystal – lattice<br />Unit Cell:<br />Smallest portion of a crystal lattice that show the 3-D pattern of the entire lattice <br />Seven types of symmetry <br />Calcite<br />Trigonal<br />Fluorite<br />Cubic<br />Emerald Hexagonal<br />Chalcopyrite Tetragonal<br />Aragonite Orthorhombic<br />Azurite Monoclinic<br />Rhodonite<br />Triclinic<br />
  9. 9. Binding forces in Crystals<br />Four Types<br />Ionic Crystals<br /><ul><li>Consist of positive and negative ions
  10. 10. Ions – monatomic or polyatomic
  11. 11. Form when
  12. 12. Group 1 or 2 metals combine with group 16 or 17 nonmetals
  13. 13. Hard and brittle
  14. 14. High melting point
  15. 15. Good insulators</li></li></ul><li>Covalent network Crystals<br /><ul><li>Covalently bonded atoms making a network with a very large number of atoms ( 3-D)
  16. 16. Examples: diamond, Quartz,
  17. 17. diamond, Quartz, silicon carbide
  18. 18. Very hard and brittle
  19. 19. Rather high melting points
  20. 20. Usually nonconductors and semiconductors</li></ul>Metallic Crystals<br /><ul><li>Metal atoms surrounded by sea of electrons
  21. 21. Hard and malleable
  22. 22. High conductivity
  23. 23. Melting points vary (very high to low)</li></li></ul><li>Covalent Molecular Crystals<br /><ul><li>Covalently bonded molecules held together by intermolecular forces
  24. 24. Examples: Nonpolar
  25. 25. Hydrogen, methane, benzene
  26. 26. Weak London dispersion forces
  27. 27. Examples: Polar
  28. 28. Water, ammonia
  29. 29. Hydrogen bonding, stronger dipole-dipole forces
  30. 30. LOW melting points
  31. 31. Easily vaporized
  32. 32. Relatively soft
  33. 33. Good insulators</li></li></ul><li>Amorphous Solids<br />Amorphous: <br />Comes from Greek word: “without shape”<br />Some amorphous solids DO FLOW<br />Very slowly<br />Example: window glass thicker on the bottom<br />Examples:<br />Glass, fiberglass, plastic<br />
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