Properties of metals, ceramics and polymers Knowledge-Based Download PDF

Questions

1. 1.

   Which of the following statements correctly compares the typical room-temperature densities and elastic (Young's) moduli of metals, ceramics, and polymers?

   • A) Metals and ceramics typically exhibit substantially higher densities and elastic moduli than polymers.
   • B) Polymers typically have higher densities than ceramics but display significantly lower elastic moduli than metals.
   • C) Ceramics typically exhibit the lowest elastic moduli of all three material classes because of their porous microstructures.
   • D) Metals typically display lower elastic moduli than polymers due to the nondirectional nature of metallic bonding.
2. 2.

   Which of the following statements accurately compares the primary environmental degradation mechanisms of metals, ceramics, and polymers?

   • A) Metals degrade primarily by photochemical chain scission, ceramics degrade via electrochemical reduction, and polymers undergo rapid galvanic corrosion.
   • B) Ceramics readily oxidize in ambient air due to low bond energies, whereas metals remain chemically inert and polymers degrade only through electrolytic pitting.
   • C) Polymers dissolve purely through galvanic cells, while metals degrade by physical swelling and ceramics break down spontaneously through ultraviolet radiation.
   • D) Metals typically degrade through electrochemical corrosion, polymers degrade through chain scission or solvent swelling, and ceramics exhibit high chemical inertness due to their stable, highly bonded states.
3. 3.

   Which of the following thermal and mechanical characteristics is uniquely typical of polymeric materials when compared to both metals and ceramics?

   • A) High elastic moduli accompanied by sharp, elevated melting temperatures well above 1000 °C
   • B) Pronounced viscoelastic behavior and relatively low operational temperatures due to the breakdown of weak intermolecular secondary bonds
   • C) Complete resistance to thermal oxidation and brittle fracture under compressive loading at ambient conditions
   • D) High thermal and electrical conductivities facilitated by freely mobile delocalized valence electron clouds
4. 4.

   Which of the following structural features accounts for the characteristic ductility and high electrical conductivity of metals compared to the brittle nature of ceramics and the insulating behavior of typical polymers?

   • A) Rigid, highly directional covalent network bonding throughout the entire lattice
   • B) Alternating ionic charges that maintain fixed crystalline positions to prevent slip
   • C) Entangled macromolecular chains held together primarily by weak intermolecular dispersion forces
   • D) A lattice of positive metal ions immersed in a sea of delocalized valence electrons
5. 5.

   Which of the following statements correctly describes the characteristic structure and physical properties of ceramics in comparison to metals and polymers?

   • A) Metals possess rigid covalent network lattices that restrict electron mobility, making them brittle electrical insulators under standard conditions.
   • B) Ceramics possess strong ionic or covalent bonds, making them hard, thermally stable, and brittle materials that typically act as electrical insulators.
   • C) Polymers possess a sea of delocalized valence electrons throughout their bulk, giving them high electrical conductivity and exceptionally high density.
   • D) Ceramics possess weak intermolecular van der Waals forces between formula units, resulting in low melting temperatures, high ductility, and rapid plastic deformation.