Intermolecular Forces, Liquids, Soldis And Materials

Question 1

Describe solids, liquids and gases

Answer 1

Solids: ordered, no diffusion, particles are close together and do not change position
Liquids: disorder, particles move and are close, slow diffusion
Gas: total disorder, lots of empty space, rapid diffusion

Question 2

Condensation polymerization

Answer 2

Formation of polymers via eliminating small molecules like HCl or H2O

Question 3

Is there a point where all phases (solid, liquid, and gas) can coexist at once?

Answer 3

Yes, the triple point occurs at a certain temperature and pressure

Question 4

What is it called when semiconductors that are inorganic compounds have their 4 valence electrons increased or decreased?

Answer 4

Doping

Question 5

When inorganic semiconductors have more than 4 valence electrons due to doping, what type of band is produced?

Answer 5

N-type (the extra electrons are added to the conduction band)

Question 6

When inorganic semiconductors have less than 4 valence electrons due to doping, what type of band is produced?

Answer 6

P-type (holes in the valence band)

Question 7

How are solar cells formed? And what type of energy are they converting?

Answer 7

By joining n-type and p-type silicon solar cells. They convert light/optical energy into electrical energy

Question 8

What type of energy do LEDs convert?

Answer 8

LEDs do the opposite of solar cells and convert electrical energy into light/optical energy

Question 9

Describe molecular solids and give an example of one

Answer 9

-low melting points and boiling points due to weak intermolecular forces
-units are molecules
-held together by intermolecular forces
-a type of crystalline solid
-ex: ice or sucrose

Question 10

Describe molecular solids

Answer 10

-low melting points and boiling points due to weak intermolecular forces
-units are molecules
-a type of crystalline solid

Question 11

Describe insulators and give some examples of them

Answer 11

-have a large band gap (the energy difference between a filled band and an empty band)

Examples: wood, air, rubber, glass and most plastics

Question 12

Describe metallic solids

Answer 12

-consist of metal atoms held together by metallic bonding
-conduct electricity
-ex: gold (Au)

Question 13

Describe ionic solids

Answer 13

-consist of positive and negative ions held together by ionic bonds
-have high melting points
-hard and brittle
-poor conductors of electricity due to the strength of ionic bonds
-ex: sodium chloride (NaCl)

Question 14

Covalent-network solids

Answer 14

-high melting points and are much harder than molecular solids
-held together by strong covalent bonds
-ex: diamond (boiling point of 3550 degrees), quartz

Question 15

Non bonding solids

Answer 15

-held together by London dispersion forces
-low melting point
-ex: xenon (Xe)

Question 16

Describe semi conductors

Answer 16

-have a small band gap so heat or radiation can promote electrons from the valence band to the conduction band
-conductivity in inorganic semiconductors can be increased by doping

Question 17

What is viscosity and how does molecular shape affect it?

Answer 17

-Viscosity is measured by a fluids resistance to flow (honey has higher viscosity than water)
-larger, more complex molecules have higher viscosities because they are more likely to interlock or entangle

Question 18

What is it called when a solid turns into a liquid?

Answer 18

Melting

Question 19

From liquid to solid

Answer 19

Freezing

Question 20

Gas to liquid

Answer 20

Condensing

Question 21

From liquid to gas

Answer 21

Boiling

Question 22

Gas to solid

Answer 22

Sublimination

Question 23

Solid to gas

Answer 23

Deposition

Question 24

Is vapour pressure higher or lower when intermolecular forces are stronger

Answer 24

Lower

Question 25

What happens at the triple and critical point?

Answer 25

At the triple point all three phases are in equilibrium and at the critical point a supercritical fluid is formed

Question 26

When does boiling occur in relation to vapour pressure?

Answer 26

When vapour pressure=external pressure

Question 27

Give some examples of Intramolecular forces, are they strong or weak?

Answer 27

-Covalent bonding, ionic bonding -They are relatively strong

Question 28

Give examples of intermolecular forces, are they strong or weak?

Answer 28

-relatively weak -London dispersion forces -Hydrogen bonding -Dipole dipole

Question 29

The stronger the intermolecular forces the lower/higher the boiling and melting points

Answer 29

Higher

Question 30

How to identify if a compound has hydrogen bonding

Answer 30

If it contains an O-H, F-H or N-H bond

Question 31

What is the strongest intermolecular force?

Answer 31

Hydrogen bonding

Question 32

When do dipole-dipole interactions happen?

Answer 32

When the positive end of a polar molecule interacts with the negative end of another polar molecule. In order to be a polar molecule the molecule must have a net dipole.

Question 33

Order the intermolecular forces in order from strongest to weakest

Answer 33

Hydrogen bonding > dipole dipole > London dispersion forces

Question 34

When are London dispersion forces present in compounds?

Answer 34

They are present in all compounds regardless whether the molecule is polar or nonpolar

Question 35

If a molecule is polar and has hydrogen bonding what does that mean?

Answer 35

It means that it has all three intermolecular forces due to the polarity

Question 36

Explain the relationship between viscosity and intermolecular forces

Answer 36

Viscosity increases with the strength of intermolecular forces

Question 37

Why does surface tension happen?

Answer 37

Because molecules at the surface are more attracted to each other than they are to the air

Question 38

Cohesive forces

Answer 38

Attraction of molecules to each other (liquid molecules sticking to each other)

Question 39

Adhesive forces

Answer 39

Attraction of molecules for surface (liquid molecules sticking to the surface)

Question 40

Are the adhesive forces between the glass (capillary) and the liquid weaker or stronger than the cohesive forces between the molecules in the liquid?

Answer 40

The adhesive forces are weaker than the cohesive forces

Question 41

Liquid crystals

Answer 41

Intermediate phases between solid and liquid, rod-shaped, polar molecules

Question 42

Nematic phase of liquid crystals

Answer 42

Aligned in one direction

Question 43

Smectic phase of liquid crystals

Answer 43

Aligned in one direction and in layers

Question 44

Cholesteric phase of liquid crystals

Answer 44

Aligned in one direction and in twisted/rotated layers

Question 45

Addition polymerization

Answer 45

Breaks down double bonds into all single bonds to form polymers from monomers