Chapter 2

Question 1

What is electronegativity?

Answer 1

The tendency of an atom to attract an electron to its outer shell.

Question 2

What is a primary bond?

Answer 2

The movement of electrons to form a stable electronic configuration

Question 3

What are the material properties of materials that are ionically bonded?

Answer 3

> High strength
High elastic modulus
High melting point
Poor electrical conductivity

Question 4

What are the material properties of materials that are covalently bonded?

Answer 4

> Very high elastic modulus
High inherent strength
High melting point
Low electrical conductivity

Question 5

What are the material properties of materials that are metallically bonded?

Answer 5

> More forgiving to deformation
> Highly electrically conductive
> High thermal conductivity
> Malleable
> Low melting point

Question 6

What is a ceramic (As in what is the material made from)?

Answer 6

Ceramics are made from a metal and a non-metal

Question 7

What bonds form within a ceramic material?

Answer 7

Ionic and covalent bonds mixed together

Question 8

What are the material properties of materials that are ceramic?

Answer 8

> Thermal and electrically insulative

> They are brittle

Question 9

What is an issue with ceramic manufacturing?

Answer 9

Flaws in the microstructure of the ceramic can be hard to control and affect material strength

Question 10

Talk about plastic deformation with regards to ceramics

Answer 10

There is very little plastic deformation before fracture making it brittle

Question 11

What are intramolecular forces?

Answer 11

Forces are between electrons and nuclei

Question 12

What are intermolecular forces?

Answer 12

Intermolecular forces are between molecules

Question 13

A bond equilibrium is reached between two atoms bonded together. Talk about this. 5 points.

Answer 13

> There is the attraction between the oppositely charged nuclei and electrons and the repulsion of the similarly charged nuclei. This affects the bond length
An equilibrium is reached and at this point the energy is lowest.
The equilibrium position is equal to the sum of the atomic radii
The internuclear separation that corresponds to the energy minimum is called the bond length
The energy required to separate the atoms to an infinite distance is the bond strength (energy)

Question 14

Name all the aspects of a force distance graph for atomic bonding

Answer 14

> Y-axis = Force
X-axis = Distance
Positive force is repulsive
Negative force is attractive
r0 is the position where the forces balance and is equal to the average length of the bond.
r > 10 × r0 = Little/no force between atoms
r < 10 × r0 = Attractive force increases
r < r0 = repulsive force dominates
Area under graph is potential energy

Question 15

How can the phase of material be determined?

Answer 15

> Using the graph of potential energy

> Determined by the balance between thermal kinetic energy (Et) and binding energy (εb)

Question 16

Where do solid materials lie on the potential energy graph? why?

Answer 16

Around the position of r0

> Bonding energy is high so the shape and volume is approximately constant

Question 17

Where do liquids lie on the potential energy graph?

Answer 17

Around 5 × r0
> Bonding energy is weak so the shape is varied
> Volume is approximately constant
> Molecules vibrate and are not fixed in place

Question 18

Where do gasses lie on the graph of potential energy?

Answer 18

Anywhere, where repulsive force dominates.
> Variable shape and volume
> Occupies all space available
> Molecules are not restrained, random motion

Question 19

What is the symbol for thermal kinetic energy and binding energy?

Answer 19

Thermal kinetic energy = Et

Binding energy = εb

Question 20

What are the equations for thermal and binding energy for each state?

Answer 20

Solid: Et < εb/10
Liquid: εb/10 < Et < εb
Gas: Et > εb

Question 21

What is a secondary bond?

Answer 21

Attractions between molecules due to uneven charge distribution between molecules

Question 22

What is an electric dipole?

Answer 22

This is the attraction between two molecules because of an uneven distribution of charge between molecules

Question 23

What is a van der waals bond?

Answer 23

It is a hydrogen bond and is due to the position of the electrons around an nucleus of an atom in a molecule

Question 24

Talk about secondary bonds with regards to polymers

Answer 24

Polymers melt easily because they have few and weak secondary bonds. The bonds are easily broken. This also gives it the ability to have a low elastic modulus.

Question 25

What is the equation for hookes law?

Answer 25

F = kx

Question 26

What is the equation for hookes law with regards to bonds in a molecule?

Answer 26

F = S0(r-r0)

Question 27

What is the equation for stress?

Answer 27

σ = F/A

Question 28

What is the equation for stress with regards to bonds in a molecule?

Answer 28

σ = S0(r-r0)/r0^2

Question 29

What is the equation for strain?

Answer 29

ε = (x-x0)/x0

Question 30

What is the equation for strain with regards to the bonds in a molecule?

Answer 30

ε = (r - r0)/r0

Question 31

What is the equation for youngs modulus?

Answer 31

E = σ/ε

Question 32

What is the equation for youngs modulus with regards to a molecule?

Answer 32

E = S0/r0

Question 33

What are the properties of a polymer? Why?

Answer 33

> low melt temperature and bonding energy
bonds readily broken and reformed by thermal energy and stress
low elastic modulus.

> This is because of ID-ID dipoles between molecules