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MAT SCI > TEST 1 > Flashcards

TEST 1 Flashcards

1
Q

Ionic bonding can be thought of as electron exchange, why?

A

Ionic bonding happens between two elements with high difference in electronegativity. The stronger element will take the electron from the weaker element.

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2
Q

What is the △EN for Ionic bonding?

A

> =1.7

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3
Q

Why is covalent bonding thought of as electron sharing?

A

Covalent bonding happens between two elements with low difference in electronegativity. The two particles will share electrons with each other to lower their potential energy.

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4
Q

What is the △EN for covalent bonding?

A

=< 1.7

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5
Q

What are dipole dipole interactions?

A

attraction between the polar sides of a molecule

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6
Q

Where are van der waals forces found?

A

Almost all organic liquids, solids, and gases; between chains in polymers

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7
Q

What is van der walls force?

A

attraction because of temporary dipoles between particles

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8
Q

Why do atoms bond?

A

Because it lowers energy

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9
Q

What happens at equilibrium separation r?

A

Energy (x) is a minimum and net force is 0

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10
Q

When is Force attractive between two atoms

A

when r is greater than equilibirum

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11
Q

When is force repulsive at equilibrium?

A

when r is smaller than equilibrium

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12
Q

what is the E at equilibrium distance r?

A

the atom-atom bond energy

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13
Q

What property can be derived from equilirbium distance r?

A

bond length

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14
Q

What property can be derived from the E at equilibrium distance R

A

Bond energy

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15
Q

What increases if E at equilibrium distance R increases?

A

Melting point

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16
Q

Do amorphous materials have higher or lower energies than crystalline materials

A

higher

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17
Q

what is a coordination number for lattice?

A

Number of nearest neighbors

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18
Q

What is a close packed plane?

A

Atomic planes with highest density

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19
Q

What is a close packed direction?

A

Direction where atoms touch

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20
Q

SC
coord#
Atom/cell
CP direction
CP plane
Lattice constant v radius

A

atoms in unit cell: 1

coord#: 6
Atom/cell: 1
CP direction: <100> (edge)
CP plane: {100}
Lattice constant v radius: a=2R

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21
Q

BCC
coord#
Atom/cell
CP direction
CP plane
Lattice constant v radius

A

atoms in unit cell: 1

coord#: 8
Atom/cell: 2
CP direction: <111>
CP plane: {110}
Lattice constant v radius: √3 a= 4 R

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22
Q

FCC
coord#
Atom/cell
CP direction
CP plane
Lattice constant v radius

A

atoms in unit cell: 1

coord#: 12
Atom/cell: 4
CP direction: <110>
CP plane: {111}
Lattice constant v radius: √2 a= 4 R

23
Q

What is atomic packing factor?

A

(Volume of all atoms in unit cell)/ volume of unit cell

24
Q

What is the radius ratio?

A

Smaller radius/ bigger radius

25
Q

Zinc Blend
Neighbor config?
Lattice constant v radii

A

Neighbor config: tetrahedral
Lattice constant v radii: Rc +Ra = (√3/4)a

26
Q

Rock Salt
Neighbor config?
Lattice constant v radii

A

Neighbor config: Octahedral
Lattice constant v radii: Rc +Ra = a/2

27
Q

Cesium Chloride
Neighbor config?
Lattice constant v radii

A

Neighbor config: Cubic
Lattice constant v radii: Rc +Ra = (√3*a)/2

28
Q

How to label planes with miller index

A

Find intercepts, take reciprocal of each intercept

29
Q

what does {hkl} mean

A

family of pklanes

30
Q

What does [hkl] mean

A

direction

31
Q

what does hkl mean

A

point

32
Q

what does <hkl> mean</hkl>

A

family of directions

33
Q

What does (hkl) mean

A

plane

34
Q

What does a system always try to do with G

A

minimize G

35
Q

What does thermodynamics dictate

A

whether a certain process can happen
G driving force needs to be positive (Gscl - Gsolid= Gdriving)

36
Q

What does kinetics dictate?

A

How fast a process can occur
Depends on kinetic barrier
Gbarrier= Gtransition-Gscl

37
Q

What does it mean to be meta stable

A

It means for a system to not be at its lowest energy state of matter and still be stable because the kinetic barrier is so high

38
Q

What is the ground state

A

lowest free energy state of matter

39
Q

Order substances in order of volume: amorphous substance, semi amorphous substance, crystalline substance

A

crystalline<semi-amorphous<amorphous

40
Q

What is glass transition state?

A

State where glass changes from rigid and glassy to soft and rubbery

41
Q

What allows elastic extensions in rubber?

A

Large chains intertwine and entangle with each other. When the chains unravel, it allows for stretching.

42
Q

Which has more energy and entropy between a random coil and extended chain

A

Extended chains will have lower energy and lower entropy

43
Q

What is Xi in polymers?

A

Mole fraction of polymer having a certain mass

44
Q

What is Mi in polymers

A

molar mass of polymer in any given section

45
Q

What data can you get from PDI?

A

condensation polymer: PDI ~2
Addition polymer: PDI~1.5-2
Advanced methods: PDI=1.001

46
Q

Can polymers be crystalline?

A

no, only semi crystalline

47
Q

What factors affect crystallinity in polymers

A

slow cooling= semi crystalline
fast cooling= amorphous

48
Q

difference between linear and branched polymer

A

linear: semi crystal
branched: amorphous

49
Q

What will increase amount of amorphous regions in a material

A

HIgher branching
faster cooling rate
bulkier side groups
atactic chain structure (chain is random)
block copolymer with long block lengths

50
Q

atactic meaning

A

R groups random possition

51
Q

isotactic

A

all r groups on same side of chain

52
Q

syndiotactic

A

r groups on alternate sides

53
Q

How would you derive young’s modulus (E) from Energy vs Interatomic spacing?

A

E is proportional to the tangential slope at equilibrium spacing R

54
Q

How would you derive CTE from E vs Interatomic spacing graph?

A

The width going from the minimum of E corresponds to CTE

MAT SCI (5 decks)

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