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Aim: I.O.SWBAT : 1)Distinguish between crystalline and amorphous solids.

Aim: I.O.SWBAT : 1)Distinguish between crystalline and amorphous solids. 2) Predict the type of solid. 3) Predict different solids general property. Motivation :. Do-Now : Complete the hand-out.

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Aim: I.O.SWBAT : 1)Distinguish between crystalline and amorphous solids.

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  1. Aim: I.O.SWBAT: 1)Distinguish between crystalline and amorphous solids. 2) Predict the type of solid. 3) Predict different solids general property. Motivation:

  2. Do-Now: Complete the hand-out.

  3. Do-Now: Give the phase of each of the following substances at room temperature. a) Aluminum b) Plastic

  4. Solids • Have both definite structures and definite volume. • There are two general groups of solids: • Crystalline solids: Particles are in highly ordered arrangement.

  5. Crystal structures are determined experimentally by X-Ray Diffraction.

  6. Find a repeating pattern.

  7. Crystalline Lattice Repeating pattern of particles Lattice point

  8. Unit cell: the smallest repeating unit in the pattern in 3-D.

  9. Primitive unit cell Primitive unit cell 1/8 of 8 atoms (ions) = 1 atom per cell In the primitive unit cell, the atoms at the corners are cut because only 1/8 belongs to that cell. The rest of the atom belongs to neighboring cells.

  10. Body-centered cubic

  11. Body-centered cubic cell (bcc) 1/8 of 8 atoms + 1 in the center 2 atoms per cell

  12. Face-centered cube (fcc) Each atom at the center of each face is shared with another cell. 1/8 of 8 atoms +1/2 of 6 atoms 4 atoms per cell

  13. How many atoms are within the unit cell below?

  14. SUMMARY Atoms at the corners = 1/8 Atoms at an edge = 1/4 Atoms at a faces = 1/2 Atoms at the center = 1

  15. Amorphous solids: No particular order in the arrangement of particles. (no crystal lattice) • Have NO definite melting pts.

  16. Complete the following chart.

  17. TYPE OF SOLIDS 1. Molecular solids: Molecules are held together by weak intermolecular forces. (dipole-dipole, london dispersion, H-bond) PROPERTIES: Soft, low m.p.(usually below 200oC) Ex. Sugar, graphite

  18. 2. Covalent network solids: • Contain no discrete molecular units. • The atoms in the network solid are held together • by covalent bonds with neighboring atoms. • The result is a single extended network. • PROPERTIES: • Hard, high m.p. • Ex. Diamond,SiO2(sand, quartz), SiC, BN

  19. Diamond: • Bond angle = 109o • Tetrahedral shape • sp3 Hybridization • Non-conductor of electricity • 3 dimensional

  20. Graphite: • Bond angle = 120o • Trigonal planar shape • Sp2 hybridization • Conductor of electricity • 2 dimensional *Graphite can conduct electricity because of delocalized electrons (P-bonds) in the benzene ring.

  21. Allotropes: Different forms of the same element that differ in bonding. Ex. C: graphite, diamond O: O2, O3 (ozone)

  22. 3. Metallic solids: • Covalent bonds between positive ions immersed in • a “sea” of delocalized valence electrons. • Hardness and m.p. depend on the number of • valence electrons. • (Wide range of hardness and m.p.)

  23. 4.Ionic solids: • Ions held together by strong electrostatic attraction. • Melting pts. depend mostly on the charge of the ions. + + HW# 40

  24. Do-Now: In terms of kinetic energy, explain why super critical fluids cannot be liquefied by increasing pressure.

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