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Chapter 14 Liquids and Solids

Chapter 14 Liquids and Solids. Three types of bonding between atoms . Covalent – electrons shared between nonmetal atoms, forms molecules or covalent crystal lattice structures such as diamond (covalent network solid)

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Chapter 14 Liquids and Solids

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  1. Chapter 14 Liquids and Solids

  2. Three types of bonding between atoms • Covalent – electrons shared between nonmetal atoms, forms molecules or covalent crystal lattice structures such as diamond (covalent network solid) • Ionic bonds – transfer of electrons between metals and nonmetals, forms ionic crystal lattice structures (ionic solid) • Metallic bonds – group sharing of loosely held electrons of metals, These electrons can migrate throughout the metal.

  3. Highest Boiling Point – crystal lattice structures (ionic or covalent) • Lowest Boiling Points – molecular compounds

  4. Crystal lattice structures • Diamond • Salt

  5. Molecular compounds • Molecules attracted to each other by: • Hydrogen bonding (strongest) • Dipole-dipole attraction (next strongest) • Dispersion forces (weakest, therefore lowest boiling point)

  6. Hydrogen bonding • The hydrogen of one molecule is “semi-bonded” to a non-bonding pair of electrons of another molecule.

  7. Requirements for hydrogen bond • 1. molecule must have hydrogen • 2. molecule must have a non-bonding pair of valence electrons (check electron-dot structure) • HF, H2O, NH3 all have hydrogen bonding, strongest intermolecular force (high melting points)

  8. Dipole-Dipole Forces • Is the attraction of the positive side of one molecule to the negative side of another molecule. • Molecule must have a dipole for this to occur • For dipole must have • Polar covalent bond • A geometry that allows for a dipole

  9. Dispersion Forces • Attraction between non-polar molecules that have a temporary dipole • Created by a temporary induced warping of the electron cloud. • Also called London dispersion forces or van der Waals forces • Is weakest of all intermolecular forces (very low boiling points)

  10. Change of state • A liquid boils when the vapor pressure (partial pressure) is equal the atmospheric pressure. • Boiling can be thought of as internal evaporation. • For a bubble to form internally it must be able to overcome atmospheric pressure.

  11. Water can be made to boil at a lower temperature by decreasing the pressure above it. • Triple point – temperature and pressure at which a substance will exist as a solid, liquid and a gas at the same time.

  12. Phase diagram of water

  13. Phase-change graph

  14. Bonds and energy • Breaking molecular or weak bonds between molecules always takes energy. • The formation of any bond always gives off energy. • At high temps there is enough energy in the system so bonds cannot form. (different temps for different bonds)

  15. Assignment • Page 492 and 493 questions 3, 4, 8, 9 – 13, 15, 17, 20, 21, 24, 25, 28, 30, 31, 33

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