CHAPTER 2 -- light

Question 1

what are secondary bonds

Answer 1

dipolar electrostatic attraction. much weaker than primary bonds.

Question 2

example of dipolar molecules and how they work.

Answer 2

H2O

one positive side while the other pole is negative

Question 3

how are materials classified by bond type?

Answer 3

metals

inorganic solids

organic solids

Question 4

metallic, covalent and ionic bonds and valence electrons : what about them?

Answer 4

metallic bonds b/n atoms w/ 1,2 or 3 valence electrons are for metals

covalent and ionic bonds b/n atoms w/ 5, 6 or 7 valence electrons are inorganic solids

Question 5

what are organic solids

Answer 5

long molecules of covalent hydrogen carbon molecules w/ secondary bonds b/n chains

hydrocarbons
asphalt, plastics and wood

Question 6

what is a crystal lattice structure

Answer 6

lattice repeating pattern of atoms
3D geometric pattern
unit cell (smallest repeating unit)

Question 7

what is a body centered cubic?

Answer 7

• each corner
• center of lattice
• 9 atoms

Question 8

what is a face centered cubic?

Answer 8

• each corner
• center of faces
• 14 atoms

Question 9

what is a hexagonal close pack?

Answer 9

• each corner
• center top and bottom face
• center place
• 17 atoms

Question 10

What are the 4 types of boundaries?

Answer 10

• coherent
• coherent strain
• semicoherent
• incoherent

Question 11

The size and arrangement of crystal grains influence the material behaviour. This mainly depends on

Answer 11

• • rate of cooling of the molten metal

- - smaller grains are formed by rapid cooling and increase toughness

Question 12

What changes the structure of materials?

Answer 12

Heat treating and plastic strains during manufacturing change grain structure

Question 13

What are alloys

Answer 13

one or more compounds dissolved in a metal

Question 14

What alloy is steel?

Answer 14

alloy of iron and carbon but frequently contains chromium, copper, nickel, phosphorous, etc.

Question 15

Alloys are possible only if the…

Answer 15

alloys are possible only if the different material have compatible crystal structures

Question 16

What are interstitial atoms?

Answer 16

atoms that fit b/n the metal atoms

must have an atomic radius less than 60% of the host metal and can dissolve only about 6% into the host

Question 17

what are substitutional atoms?

Answer 17

takes the place of a host atom in the lattice. if atoms are similar enough, compounds mix easily.

Question 18

what are the three axis of a phase diagram?

Answer 18

x : temperature
y : pressure
z (sometimes) : brine composition (%)

Question 19

what are binary phase diagrams?

Answer 19

phase diagram that displays relationship b/n percent of elements et transition temperatures

Question 20

phase diagrams exist for what kind of mixtures?

Answer 20

soluble
partly soluble and
insoluble

Question 21

Definition of Eutectic?

Answer 21

Sudden transition from liquid to solid w/out a 2phase region. On a phase diagram.

Question 22

Define ceramics

Answer 22

• • high strength
• • high durability
• • brittle due to bonding (covalent or ionic)

Question 23

What are glasses?

Answer 23

based on silica and have a random or amorphous but very stable structure

Question 24

What are vitreous ceramics?

Answer 24

Clay products like pottery, bricks, etc.

Question 25

What are high-performance ceramics?

Answer 25

Expensive, highly refined materials specially developed to have very specific properties

Question 26

2 other classes of inorganic solids?

Answer 26

cement and concrete

rocks and minerals

Question 27

The mechanical properties of organic solids depend on

Answer 27

• • polymer chain length
• • extent of cross-linking (non-reversible)
• • type of radical compounds linked to the H-C

Question 28

What is a Mer?

Answer 28

repeating unit in a polymer chain

Question 29

What is a monomer?

Answer 29

a single mer-unit (n=1)

Question 30

What is a polymer?

Answer 30

Many mer-units along a chain (n=10^3 or more)

Question 31

What is a degree of polymerization?

Answer 31

average number of mer-units in a chain

Question 32

3 types of chain structures for polymers

Answer 32

linear
branched
cross-linked (e.g. PEX)

Question 33

4 classes of organic compounds

Answer 33

thermoplastics
thermosets
elastomers or rubbers
natural polymers

Question 34

describe thermoplastics + examples

Answer 34

transition from elastics to viscous plastic behavior when heated as the cross-link bonds b/n chains melt.

ex : asphalt PVC, polyethylene, polypropylene, polystyrene, teflon, etc.

Question 35

describe thermosets + examples

Answer 35

chemical rxn to harden stable cross-links that don’t soften when heated

ex : epoxy, polyesters, phenol-formaldehyde, Formica.

Question 36

describe + examples for elastomers or rubbers

Answer 36

limited cross-linking
flexible structure

ex : polyisoprene (natural rubber, silicone), polybutadiene (synthetic rubber) and polychloroprene (Neoprene)

Question 37

what are natural polymers?

Answer 37

wood

Question 38

2 other types of polymer chain structures?

Answer 38

ordered structure linear polymer

cross linked structure linear polymer