Unit 1

Question 1

At molecular level what determines whether a material will be solid liquid or gas?

Answer 1

Competition between intermolecular forces of attraction and kinetic energy of molecules

Question 2

In the lennard jones potential energy equation what are the typical values for m and n

Answer 2

M=6

N=12

Question 3

What are liquid crystals

Answer 3

Liquids that have a long range order an so they behave like solids in many temperatures

Question 4

What does asymmetry in molecules give rise to?

Answer 4

Unsymmetrical or anisotropic packing

Question 5

Three examples of colloidal dispersions?

Answer 5

Milk butter mayonnaise

Question 6

Why is glass different than a normal solid?

Answer 6

Its amorphous- solid but not a crystal structure

Question 7

Is a body centered cubic structure close packed?

Answer 7

No

Question 8

What is the closest packing of atoms/

Answer 8

Hexagonal close packing

Question 9

What has higher packing efficiency, hexagonal or body centered?

Answer 9

Hexagonal

Question 10

Coordination number of simple cubic and number of atoms in unit cell?

Answer 10

c#=6

a#= 1

Question 11

Hexagonal close packed coordination number?

Answer 11

12

Question 12

Coordination number of face centred cubic and

Answer 12

c#=12

a#= 4

Question 13

How many bravais lattices are there?

Answer 13

14

Question 14

What is the most stable coordination number for crystals

Answer 14

12

Question 15

Why do manufactures sometimes add impurities to crystals?

Answer 15

Better physical or chemical properties

Question 16

What is van der waals radius

Answer 16

Touching distance between molecules

Question 17

Coordination number of body centered cubic and atoms per unit cell?

Answer 17

#c=8
a#= 2