Flashcards
HW 8
Cards in this deck (17)
- 1Which of these statements is NOT true about glasses? Cooling a glass melt faster can lead to forming a glass with a higher fictive temperature. Adding chemical modifiers with high atomic number to an SiO2 glass will usually increase the refractive index of the glass. Adding chemical modifiers to SiO2 glass increases the amount of bonding in the glass network and usually raises the glass transition temperature. If you change the chemical composition of a glass, you will likely change the glass transition temperature of that glass. Glasses of the same composition but different fictive temperatures can have different thermal conductivities.Adding chemical modifiers to SiO2 glass increases the amount of bonding in the glass network and usually raises the glass transition temperature.
- 2Compared to a completely amorphous polymer of the same composition, a semi-crystalline polymer is expected to: (I) have greater optical transparency. (II) show improved stability to higher operating temperatures. (III) appear more uniformly colored after dying. (IV) exhibit a higher elastic modulus. (V) be a better vapor barrier when used in food packaging.(ii) (iv) & (v)
- 3—Grafted Copolymer
- 4—Syndiotactic
- 5—Monomer C
- 6In window glass, silicon is... octahedrally coordinated to 6 oxygens. tetrahedrally coordinated to 4 oxygens. octahedrally coordinated to 4 oxygens. hexagonally coordinated to 6 oxygens.tetrahedrally coordinated to 4 oxygens.
- 7Semicrystalline polymers are opaque because... the crystallites absorb light. the amorphous regions diffract light. the amorphous regions absorb light. the crystallites transmit light. the crystallites scatter light.the crystallites scatter light.
- 8Adding cross-links to a polymer will... will make the polymer more rigid. will make the polymer atactic. transform it into a thermoplastic. will add branches to the polymer.will make the polymer more rigid.
- 9True/False: If two glasses have identical compositions, they will also have identical properties.False (consider quenching)
- 10"Super balls" that bounce really high are an example of... a thermoplastic polymer with its Tg below room temperature. a thermoset polymer with its Tg above room temperature. a thermoplastic polymer with its Tg above room temperature. a thermoset polymer with its Tg below room temperature.a thermoset polymer with its Tg below room temperature.
- 11The glass transition temperature is always below the melting temperature of a material.True
- 12—Both B & D
- 13True/False: Amorphous solids have short range order.True
- 14True/False: Hydrogels dissolve in water.False
- 15Ceramic glasses A and B have the same composition but glass A has a higher fictive temperature than glass B. Which of these statements could be accurate about these two glasses? Glass A and B were likely quenched from the same temperature, but glass A is less dense than glass B. Glass A was quenched from a lower temperature than glass B, leading to glass A being less dense than glass B. Glass A and B were likely quenched from the same temperature, but glass A is more dense than glass B. Glass A was quenched from a lower temperature than glass B, leading to glass A being more dense than glass B. Glass A was quenched from a higher temperature than glass B, leading to glass A being less dense than glass B. Glass A was quenched from a higher temperature than glass B, leading to glass A being more dense than glass B.Glass A was quenched from a higher temperature than glass B, leading to glass A being less dense than glass B.
- 16Adding a PbO modifier to SiO2 glass will result in a new glass that has... ...a lower refractive index and a lower glass transition temperature than pure SiO2 glass. ...a higher refractive index and a lower glass transition temperature than pure SiO2 glass. ...a higher refractive index and a higher glass transition temperature than pure SiO2 glass. the same properties as the pure SiO2 glass. , Not Selected ...a lower refractive index and a higher glass transition temperature than pure SiO2 glass....a higher refractive index and a lower glass transition temperature than pure SiO2 glass.
- 17Which of these techniques could be used to probe the short range order in window glass? A. Using UV-vis spectroscopy to measure the transmission spectrum. B. Using x-ray scattering to collect a radial distribution function. C. Using X-ray diffraction to examine the interplanar spacing. D. Window glass does not have any short range order to probe. E. Both B & CB. Using x-ray scattering to collect a radial distribution function.