material science exam 2

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material science exam 2
2013-03-25 13:28:44
material science

material science exam 2
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  1. In which way was the classical knowledge that had been lost during Dark Ages recovered?
    The Muslims conquered East Roman empire about 700 AD, they took over and carefully preserved the bulk of the Greek books and knowledge they found there, while in West Roman Empire, book burning destroyed all the "heathen," or "pagan" knowledge by 500 AD. Through the Crusades, the West became reacquainted with their own heritage of knowledge.
  2. Before the invention of the steam engine, most labor was performed by humans, animals, wind or water power. What particular work in connection with mining and metallurgy was frequently done by HORSES?
    Hauling ore out of mine and working bellows to fan fires or providing fresh air for miners underground
  3. The Muslim Moors in Spain discovered a method of making copper with only modest heating. How was this done?
    They roasted copper sulfide ores, thereby oxidizing them into CuSO4 (blue vitriol) in water which yields the blue solution demonstrated in class, and ran over scrap iron, whereby the copper plates out on the iron and can be scraped off.
  4. The Industrial Revolution was triggered by the invention of machines, beginning with the steam engine, which could substitute for human labor. Before then, human labor was assisted by WATER power and HORSE power. Give at least one example for each.
    Water wheel: water flowing through are reasonably sized height differential turns a wheel. Various tools may be attached to the axel that perform work. Ex. crushing of ores in a stamping mill. Horses help operate bellow for a smith.
  5. Iron-making was already widespread in Europe. True or false
  6. The iron pillar of Delhi is made of wrought iron and does not rust. True or false
  7. In Louis XIV's palace of Versailles in France, there are still operative cast iron water pipes. True or false
  8. Names at least 2 early industrial uses of water power.
    Stamping power (for crushing ores or pig iron). Auxiliary aid in wire drawing. Operating bellows for fanning fire. For example, in smithing
  9. In Elizabethan England there was a severe "energy crisis." What was it, how was it caused and how was it resolved?
    Rapidly rising iron production depleted the forests of mature trees because the blast furnaces required charcoal gained from wood. Consequently the price of fuel wood for heating and cooking rose steeply. The discovery that coal could be converted to coke, much like wood to charcoal, and that coke could be used in blast furnaces resolved the crisis
  10. Name at least 3 important methods for metal forming
    • 1. Casting (molten metal into forms)
    • 2. Forging/swaging/hammering 
    • 3. Cutting methods (turning into a lathe, grinding, drilling, milling)
    • 4. Drawing (of sheets, to make cars for example. making car bodies, air plane bodies)
  11. The critical difference between a metal and a non-metal is the manner in which the atoms are bound together. What are the three basic forms of bonding?
    Metallic, ionic, covalent
  12. The critical difference between a metal and a non-metal is the manner in which the atoms are bound together. Which of the three basic forms of bonding is the bonding of metals? How does it work?
    Metallic. In this bonding, the outermost electrons ("conduction electrons") are shared among the atoms without fixed positions and serve almost like a glue.
  13. The critical difference between a metal and a non-metal is the manner in which the atoms are bound together. In which way is the bonding responsible for the typical metallic properties?
    In the metallic bonding, therefore, the conduction electrons are highly mobile. As a result a metal readily conducts current, as well as heat, is a good electrical as well as heat conductor.
  14. Metals tend to have a tight-packed structure because their ions attract each other. True or false?
  15. An ion is a charged electron. True or false?
  16. The energy of an electron in a solid is "quantized." True or false?
  17. At low temperatures, the Fermi energy is the highest energy an electron can have. True or false?
  18. Insulators tend to be opaque because light interacts with their free electrons. True or false?
  19. Sodium is held together by ionic bonds. True or false?
  20. Metals are opaque because light interacts with their electrons. True or false?
  21. Electrons are shared by atoms in covalent bonds. True or false?
  22. At what electron energy is it most likely to find valence electrons in solids?
    At the Fermi energy
  23. Describe the standard model of a metal.
    The standard model of a metal is that of a crystal lattice structure of ions (ionized atoms) embedded in a "gas" of electrons that have been removed from the individual atoms so as to be shared by all ions and fill all space between them, which assembly of electrons is called a Fermi Gas.
  24. Name and sketch all three types of bonding.
    Ionic, covalent, metallic.
  25. The free electron gas model explains, above all:
    why metals are great conductors of electricity and heat
  26. Briefly describe a) what conduction electrons are and b) what their function is
    a) the neutral atoms of metals, when in isolation, have 1 to 3 loosely bound electrons in their outer shells called "conduction electrons." In the solid metal, these conduction electrons are shared among the atoms without fixed positions, and thus are mobile, almost like a gas

    b) the easy mobility of conduction electrons gives metals their good electrical and heat conductivity. Sharing of electron provides the metallic bond
  27. Why are insulators transparent to visible light?
    Light is absorbed by freely movable electrons, ie. pre-eminently the conduction electrons of metals, whereas there are no free electrons in insulators.
  28. Part of the genius of human progress is our ability to
    convert one form of energy into another form for doing usable work.
  29. A useful statement of First Law of Thermodynamics is
    energy cannot be created or destroyed.
  30. A modern view is that heat should be viewed as energy in transit across the boundaries of materials and that process of heat transfer involves random interactions at the molecular level, involving temperature difference. True or false?
  31. Indicate the major steps involved in winning a metal from its ore, beginning with the ore being delivered to the processing facility and ending with the finished metal.
    • 1. Excavating or mining the ore.
    • 2. Hauling to processing plant. Sorting out obvious “tailings” and discarding them.
    • 3. Milling extremely finely.
    • 4. Separate the remaining “tailings” via floatation (e.g., baking soda).
    • 5. Processing so as to “reduce” the ore (mainly through heating but sometimes also making use of electrolysis).
    • 6. Iron Ore is first processed into marble sized pellets and shipped to a blast furnace to be
    • reduced into metallic iron (pig iron).
  32. Explain the rapid evolution of steel making in England beginning in the Renaissance that gave rise to a severe "energy crisis".
    Steel-making requires a lot of clean fuel, and charcoal was the only option, which was obtained from wood and prolonged heating under exclusion of air. This drives out the sap and impurities in the form of tar. To satisfy the increasing demand for iron and steel, trees were felled at a much faster rate than they could regrow. Wood became scarce and expensive.

    The crisis was resolved when it was discovered that coal could be purified in a similar manner as wood, thereby discovering and producing coke that can be used for blast furnaces.
  33. What is the distinguishing feature of metals, and what is metallic bonding?
    In the neutral state, single metal atoms have one, two, or three loosely bound electrons in their outermost shells. They're called conduction electrons, and in the metallic state are shared among atoms without fixed positions. Thereby atoms are held together in a "metallic bond."
  34. What are metal "ores"?
    Ores are chemical compounds (often intermixed with “tailings”) which contain metals that are chemically bound such as to lend one, two or three of their outermost electron(s) to non-metals. very often oxygen.
  35. What is meant by oxidation, specifically of a metal?
    In the chemist’s language, “oxidation” means a chemical reaction in which one or more electrons per atom are lent to another element. Thus in ores metals are present in “oxidized” form, even if they are bonded with sulfur, phosphorous etc.
  36. The bulk of all our metals are "reduced" from their ores, what does this mean and what treatments are typically involved?
    Winning the metal from the ore means "reducing" them, which means reversing oxidation through giving them back their electrons. This typically involves high heat, such as in blast furnaces, and it requires "fluxes," which means chemical elements or compounds that bind non-metals from ores and thereby return the electrons back to metal atoms
  37. Why are metals overwhelmingly found in the form of ores?
    Oxidization in the form of “weathering” and corrosion of base metals takes place spontaneously and over the vast geological time span has bound metals into ores
  38. In terms of electrons how are metals extracted from ores?
    Metals are extracted from ores by “reduction”, i.e. giving back to the metal atoms the electrons that in the ores they had lost through “oxidation”. Typically but not always this requires elevated temperatures (in blast furnaces provided by burning coke) and the use of materials that accept the electrons and in the process form “slags” (e.g. lime stone in blast furnaces)
  39. What are the metals/minerals predominantly won in deep mining?
    Noble metals: gold, platinum, rhodium
  40. Chemically, when a metal is "reduced" from its ore, do the metal gain or lose electrons?
  41. In a demonstration of elastic behavior, five helical spiral springs of identical shape but painted in different colors were shown to elastically extend by different amounts when loaded with a 100, 200 and 500 gm weight. What is the cause? What has Hooke’s law to do with this? Please explain.
    The springs were made of different metals and therefore their elastic moduli were different. Specifically, according to Hooke's law, tensile stress = tensile strain times Young's modulus. For the same load, ie. same stress, the elongation, ie. strain, is inversely proportional to the elastic modulus.
  42. State Hooke's law.
    In elastic straining, stress and strain are proportional to each other.
  43. Very briefly discuss Hooke's law for the cases of simple tension. Give the relevant equations and outline the geometry involved.
    Hooke's law states that before the onset of permanent/plastic deformation, forces and deformations are proportional to each other, in the simple geometries of tension as shown in class. This means that, in ELASTIC deformation, the tensile stress is proportional to tensile strain. The proportionality factors between stress and strain are called "elastic moduli." 100% elastic strain can never be achieved because the material either deforms plastically or fractures long before.
  44. What is a lattice vacancy?
    Crystal that is empty
  45. What is a crystal location?
    A line defect that by its motion glide by one atomic spacing over the area over which it has moved
  46. How does the equilibrium concentration of vacancies in a crystal vary with temperature?
    It increases with increasing temperature
  47. Atomic diffusion is mostly defined by the
    mobility of point defects, the vacancy.
  48. Strength is related to which axis?
  49. The straight lines plotted for each of the materials are a representation of 
    Hooke's law
  50. Each line shown for the materials ends abruptly as the stress increases. This endpoint is referred to as:
    elastic limit
  51. The strain is a measure of?
    stretch or elongation
  52. The age that had the material with the highest elastic modulus is the
    Iron Age
  53. Work hardening results from
    dislocations multiplying and interacting during plasticity
  54. Dislocations start to move at a stress
    near the x on the stress axis
  55. The elastic limit for the material tested is nearest to 
    near the x on the stress axis
  56. Dislocations will glide on which plane in FCC metals
  57. What do pillar of Delhi and the woodcut have in common?
    wrought iron
  58. What do you call a lump of iron?
  59. Which bonds are hard and brittle?
    Ionic and covalent
  60. The essential defects for any deformation when a metal is hammered into a useful shape are: 
  61. The reason the Bronze Age replaced the Chalcolithic (Copper) Age is because: 
    Bronze is stronger than copper
  62. In the “The Ascent of Man” video we watched during class, the narrator compared the addition of tin to copper to be like adding ____49____ to the copper, which increases the alloy’s strength. 
    atomic grit