Department of Chemistry CHEM1020 General Chemistry ***********************************************

1. Department of Chemistry CHEM1020 General Chemistry *********************************************** Instructor: Dr. Hong Zhang Foster Hall, Room 221 Tel: 931-6325 Email: hzhang@tntech.edu

2. CHEM1020/General Chemistry_________________________________________Chapter 11. (L19)-Chemistry of Earth • Today’s Outline …The earth’s surface …Earth’s lithosphere elemental composition of lithosphere inorganic substances, minerals organic substances …Silicates …Modified silicates

3. Chapter 11. (L19)-Chemistry of Earth • The Earth surface …Structure of the earth core (Fe, Ni) mantle (silicates) crust (earth surface) …Earth surface lithosphere (primary silicates) pedosphere (secondary silicates) biosphere (biomolecules) atmosphere (gases) hydrosphere (water)

4. Chapter 11. (L19)-Chemistry of Earth • Earth’s lithosphere …lithosphere physical feature: 35 km thick under continents 10 km thick under oceans …Elemental composition of lithosphere (percent by mass) O, 49.5%; Si, 25.7%; Al, 7.5% Fe, 4.7%; Ca, 3.4%; Na, 2.6% K, 2.4%; Mg, 1.9%; H, 0.9%; all others, 1.4% …Oxygen of the earth surface in hydrosphere in water in lithosphere in silicates in atmosphere as oxygen gas (O2)

5. Chapter 11. (L19)-Chemistry of Earth • Earth’s lithosphere …lithosphere rocks igneous rocks sedimentary rocks metamorphic rocks rock cycle: the grand geochemical cycle rocks are composed of minerals, inorganic substances major mineral types: silicate minerals (metals with Si and O) carbonate minerals (metals with C and O) oxide minerals (metals with O) sulfide minerals (metals with S)

6. Chapter 11. (L19)-Chemistry of Earth • Earth’s lithosphere Inorganic substances minerals Organic substances coals natural gases petroleum oil shale

7. Chapter 11. (L19)-Chemistry of Earth • Earth’s lithosphere Some nonsilicate minerals of economic importance Mineral TypeNameFormulaUse Oxide hematite Fe2O3 iron ore megnetite Fe3O4 iron ore cornudum Al2O3 gemstone Sulfide galena PbS lead ore chalcopyrite CuFeS2 Cu ore cinnabar HgS Hg ore sphalerite ZnS Zn ore Carbonate calcite CaCO3 cement lime

8. Chapter 11. (L19)-Chemistry of Earth • Calcium carbonate: Limestone …Various calcium carbonates in nature marbles, seashells, eggshells, calcite, coral …Limestone (CaCO3) Dissolution of limestone in nature CaCO3 + CO2 + H2O = Ca2+ + 2HCO3- chemistry of cave formation

9. Chapter 11. (L19)-Chemistry of Earth • Silicates …Basic unit of silicates: an SiO4 tetrahedron similarity between C and S C-H tetrahedron: the backbone of biosphere S-O tetrahedron: the backbone of lithosphere … an SiO4 tetrahedron much like methane: CH4 Si-O bond, 4 bonds of Si with 4 O angle: 109.5º

10. Chapter 11. (L19)-Chemistry of Earth • Silicates Some common silicates (Table 11.3) Quartz: 3D silicates, pure silicon dioxide (SiO2) sand, gems 3D-structure of SiO4 tetrahedron Micas: sheet silicates SiO4 tetrahedron arranged in 2D sheets the sheets are bound together by Al3+ Asbestos: linear SiO4 tetrahedron arranged in chain two chains bound by oxygen to form double- chain structures; the double-chains bound by Mg2+ fibrous, best known example: chrysotile, a magnesium silicate excellent insulator

11. Chapter 11. (L19)-Chemistry of Earth • Silicates Hazardous effects of asbestos …inhalation of asbestos fibers can cause various lung diseases and cancers cigarettes can increase the risks significantly crocidolite is responsible for the hazardous effects chrysotile, 95% of the asbestos used in USA, perhaps appears to be less dangerous …Regulations that requires removal of asbestos from schools and other public buildings

12. Chapter 11. (L19)-Chemistry of Earth • Modified silicates …Ceramics Inorganic materials made by heating clays or other mineral matter to a high temperature at which the particles of clays partially melt and fuse together natural clays: Al silicates bricks, tiles, cooking pots, water jugs, mugs, specialty materials: high heat-resistance ceramics (rocket nose cones, surface tile) super-conductance ceramics

13. Chapter 11. (L19)-Chemistry of Earth • Modified silicates …Glass A non-crystalline solid, a mixture of sand (silicates), sodium carbonate (Na2CO3), and limestone heated at high temperature to form a homogeneous liquid and after it cools, it becomes glass Properties: irregular arrangement of 3D SiO4 tetrahedra by various kinds of chemical bonds; When heated, glass gradually softens The basic ingredients of glass can be used in different proportions and various kinds of metals oxides can replace one or more of the basic ingredients to form many special types of glass (Table 11.4) Optical fibers, pure threads of glass as thick as hair

14. Chapter 11. (L19)-Chemistry of Earth • Modified silicates …Cement and concrete Cement: a complex mixture of calcium and aluminum silicates raw materials for cement: limestone and clay Concrete: cement mixed with sand and gravel Our understanding of the complex chemistry of cement still remains imperfect. Production of cement is highly energy-consuming roads destroy our green heritage

15. Chapter 11. (L19)-Chemistry of Earth Quiz Time Make up three or more quiz questions based on the content of this lecture together with the answer of four choices to each quiz question.