Deck 12: Modern Materials

Question 1

The formation of a condensation polymer generally involves _ .

A) the addition of a plasticizer
B) the formation of significant crosslinking
C) the elimination of a small molecule
D) the mixing of sulfur with an addition polymer
E) the vaporization of a plasticizer

Answer 1

the elimination of a small molecule

Question 2

In the context of biopolymers, the opposite of the polymerization process is .

A) addition
B) condensation
C) cross- linking
D) hydrolysis
E) sublimation

Answer 2

hydrolysis

Question 3

In initial steps of the sol- gel process, a reactive metal is treated with an alcohol to form a metal alkoxide. The metal alkoxide is then combined with water to form the metal hydroxide. The metal hydroxide is not formed directly by reaction of the metal with water because .

A) the direct reaction of a reactive metal with water will give a complex mixture of metal oxides and hydroxide
B) finer particles are obtained in the two- step process
C) the two- step process prevents oxidation of the metal to an unstable oxidation state
D) the metal hydroxide formed in the two- step process is more soluble and is more easily utilized
E) the alcohol stabilizes the metal hydroxide making it less susceptible to attack by the base added later

Answer 3

the direct reaction of a reactive metal with water will give a complex mixture of metal oxides and hydroxide

Question 4

Biocompatibility means that material is .

A) made by biological methods
B) integratable into living organisms
C) made from biological material
D) biodegradable
E) none of the above

Question 5

Materials that eventually break down in the body .

A) are always toxic
B) cannot be used as biomaterials
C) can be used to construct "scaffoldings" on which natural cells grow
D) can be used to construct bone- replacements
E) can be used to construct long- term replacements for heart valves

Question 6

Molecules with only single bonds do not generally exhibit liquid- crystalline properties because
)

A) molecules without multiple bonds lack the flexibility necessary for alignment
B) molecules with only single bonds are gases
C) molecules without multiple bonds lack the rigidity necessary for alignment
D) molecules with only single bonds are too big to exhibit liquid- crystalline properties
E) molecules without multiple bonds are too small to exhibit liquid- crystalline properties

Question 7

A biomaterial intended for use as a long- term replacement of a blood vessel _ .

A) must be rigid and chemically inert
B) must be flexible and have an open porous structure
C) should be designed such that it encourages coagulation of blood
D) must be rigid and must not degrade over time
E) must be rigid and have rough surfaces

Question 8

Natural rubber is too soft and chemically reactive for practical applications. Vulcanization of natural rubber entails _ .

A) crosslinking reactive polymer chains with sulfur atoms
B) increasing the average molecular weight of a condensation polymer
C) decreasing the average molecular weight of an addition polymer
D) conversion of an addition polymer to a condensation polymer
E) conversion of a condensation polymer to an addition polymer

Question 9

For a given substance that exhibits liquid- crystalline properties, the liquid- crystalline state exists
)

A) in a range of temperatures above the melting point of the solid
B) in a range of temperatures from below the melting point to above the melting point
C) at one particular temperature below the melting point of the solid
D) in a range of temperatures below the melting point of the solid
E) at one particular temperature above the melting point of the solid

Question 10

Which of the following is most likely to exhibit liquid- crystalline behavior?

A)

B) CH₃CH₂CH₂CH₂CH₂CH₂CH₂CH₃
C) CH₃CH₂CH₂CH₂CH₂- Na⁺
D) CH₃CH₂- C(CH₃)₂- CH₂CH₃
E)

Question 11

As a polymer becomes more crystalline, _.

A) its density decreases
B) its stiffness decreases
C) its melting point decreases
D) its yield stress decreases
E) none of the above are correct

Question 12

A biomaterial intended for use as a long- term replacement of a bone must .

A) have sufficient rigidity
B) be chemically inert
C) possess all of these qualities
D) not degrade over time
E) not cause an immune response

Question 13

In what year was the first systematic work involving liquid crystals reported?

A) 1776
B) 1954
C) 1943
D) 1978
E) 1888

Question 14

Advantages to replacement of metal parts used in high- temperature applications with ceramics include:
1) Ceramics are easily manufactured free of defects.
2) Ceramics are less dense than metals.
3) Ceramics are less brittle than metals.
4) Ceramics are more resistant to corrosion than metals.

A) 2, 3, 4
B) 1, 2, 4
C) 2, 4
D) 1, 2, 3, 4
E) 1, 3, 4

Question 15

An elastomer will fail to regain its original dimensions following a distortion beyond its

A) phase boundary
B) glass transition
C) London force
D) crystallinity
E) elastic limit

Question 16

Cholesteric liquid crystals are colored because .

A) of the slight twist between layers
B) All of the molecules contain multiple benzene rings.
C) of the large spacing between layers
D) each molecule is a chromophore
E) of the large number of conjugated bonds

Question 17

Cholesteric liquid crystals have not been used for monitoring of .

A) skin temperature
B) all of the above
C) hot spots in microelectronic circuits
D) temperature of light
E) temperature of cookware

Question 18

Of the following chemical forms, are not commonly found in ceramics.

A) silicates
B) carbides
C) nitrates
D) oxides
E) aluminates

Question 19

Superconductivity means that .

A) electrons move faster
B) electrons move through a shorter path
C) electrons move without resistance
D) super expensive materials were used
E) diamagnetic atoms become elongated

Question 20

The material first shown to exhibit what we now call superconductivity was _ .

A) a metal
B) a composite
C) a ceramic
D) a polymer
E) a thin film

Question 21

are solid- state materials that can be made either semiconducting or metallic without any doping.

Question 22

are materials characterized by an energy gap between a filled valence band and an empty conduction band.

Question 23

The process of adding controlled amounts of impurity atoms to a material is known as
.

Question 24

Nylon is formed by the reaction of a with a .

Question 25

Which of the following is not a natural polymer? silk
Starch protein cellulose nylon

A) cellulose
B) protein
C) starch
D) silk
E) nylon

Question 26

The empirical formula of an addition polymer .

A) is the same as that of the monomer from which it is formed except that 2 H and 1 C have been added
B) is the same as that of the monomer from which it is formed except that 2 H and 1 O have been subtracted
C) is the same as that of the monomer from which it is formed except that 2 H and 1 C have been subtracted
D) is the same as that of the monomer from which it is formed
E) is the same as that of the monomer from which it is formed except that 2 H and 1 O have been added

Question 27

For a given substance that exhibits liquid- crystalline properties, the transition from solid to liquid- crystal state occurs .

A) over a range of temperatures between the melting point of the solid and the boiling point of the liquid
B) at a well defined temperature above the melting point of the solid
C) at a well defined temperature below the melting point of the solid
D) at the melting point of the solid
E) over a range of temperatures that includes the melting point of the solid

Question 28

A sample of natural rubber (200.0 g) is vulcanized, with the complete consumption of 4.8 g of sulfur. Natural rubber is a polymer of isoprene (C₅H₈). Four sulfur atoms are used in each crosslink connection. What percent of the isoprene units will be crosslinked?

A) 1.3
B) 9.4
C) 2.5
D) 7.6
E) 5.1

Question 29

A material is sintered by .

A) sieving to achieve uniform particle size
B) finely dividing the solid
C) heating the finely divided solid to a high temperature under pressure
D) placing in the middle
E) heating with sulfur

Question 30

The monomer that is polymerized to make natural rubber is .

A) ethylene
B) adipic acid
C) formaldehyde
D) melamine
E) isoprene

Question 31

Short, high purity fibers reinforced with aluminum borosilicate fibers are used to manufacture the space shuttle tiles.

Question 32

Which of the following is not a biopolymer? protein
Polysaccharide polyurethane RNA
DNA

A) RNA
B) DNA
C) protein
D) polyurethane
E) polysaccharide

Question 33

MRI stands for .

A) Magnetic Resonance Imaging
B) Meissner Resonance Inductance
C) Material Research Instrument
D) Material Resistive Impedance
E) Me Really Imaginative

Question 34

A _ _ liquid crystal has the least order and is the most liquid- like.

A) smectic B
B) cholesteric
C) nematic
D) smectic C
E) smectic

Question 35

In the smectic A liquid- crystalline phase, _ .

A) the molecules are oriented in a totally random fashion
B) the molecules are aligned with their long axes tilted with respect to a line perpendicular to the plane in which the molecules are stacked
C) disk- shaped molecules are aligned through a stacking of the disks in layers
D) the molecules are aligned along their long axes, with no ordering with respect to the ends of the molecules
E) the molecules are arranged in sheets, with their long axes parallel and their ends aligned as well

Question 36

Write the chemical formulas for both polyethylene and the monomer from which it is formed.

Question 37

A category plastic container will generally be the most easily recycled.

A) 1
B) 2
C) 3
D) 4
E) 22

Question 38

Which one of the following is an addition polymer with the same structure as polyethylene except that one hydrogen on every other carbon is replaced by a benzene ring?
Polyvinyl chloride polypropylene polystyrene polyurethane nylon 6,6

A) polystyrene
B) polypropylene
C) nylon 6, 6
D) polyvinyl chloride
E) polyurethane

Question 39

Of the following, only is not a polymer. cellulose
Nylon starch protein
Stainless steel

A) cellulose
B) nylon
C) starch
D) protein
E) stainless steel

Question 40

Which type of liquid crystal is colored and changes color with temperature?

A) smectic A
B) smectic B
C) smectic C
D) nematic
E) cholesteric

Question 41

There are different amino acids present in most proteins.

A) 1
B) 2
C) 99
D) 16
E) 20

Question 42

Molecules containing only single bonds do not exhibit liquid- crystal behavior because free rotation can occur around single bonds making these molecules flexible.

Question 43

A plasticizer makes a polymer more pliable by reducing the interactions between polymer chains.

Question 44

Silicon technology is based on the fact that silicon oxide is a chemically stable conductor.

Question 45

Superconductors exhibit the Meissner effect.

Question 46

Vulcanization involves heating rubber with sulfur dioxide to produce a thermosetting polymer.

Question 47

Polyethylene is formed by a condensation reaction.