Chapter 10 - Solids and Liquids

Question 1

Describe Hydrogen Bonding

Answer 1

An unusually strong dipole formed by the bonding of hydrogen and either Oxygen, Nitrogen, or Fluorine

Question 2

What factors lead O N and F to form the strongest Hydrogen Bonds?

Answer 2

Relatively high eletronegativities and small size

Question 3

Between which substances are London Dispersion Forces the strongest?

Answer 3

Nobel Gases or non-polar molecules

Question 4

Under what conditions do LDFs exist under in Nobel Gases and non-polar molecules?

Answer 4

Either low temperatures or high pressures, when the molecules are in close proximity

Question 5

What consequence do LDFs have on Nobel Gases and non-polar molecules?

Answer 5

Lower freezing points result, as molecules must be very close for the LDFs to have a large effect

Question 6

Explain Polarizability

Answer 6

The probability of electrons temporarily aligning in a dipole in an atom

Question 7

What is the trend of polarizability in a group?

Answer 7

It increases going down a group

Question 8

Explain Surface Tension

Answer 8

A measure of a liquid’s resistance to an increase in its surface area

Question 9

What is the significance of a concave meniscus?

Answer 9

It means that adhesive forces are stronger than cohesive forces

Question 10

What is the significance of a convex meniscus?

Answer 10

It shows that cohesive forces are stronger than adhesive forces

Question 11

Explain Capillary Action

Answer 11

The spontaneous process by which liquids rise upward in a narrow tube

Question 12

What are Cohesive Forces?

Answer 12

Intermolecular forces acting between molecules of the same substance

Question 13

What are Adhesive Forces?

Answer 13

Intermolecular forces occurring between molecules of two or more different substances

Question 14

Explain the concept of Viscosity

Answer 14

Viscosity is a measure of a liquid’s resistance to flow

Question 15

How do molecular complexity and hydrogen bonding contribute to viscosity?

Answer 15

Complex molecules cannot slide past each other as easily as planar molecules; hydrogen bonding creates strong dipoles which created unusually strong cohesive forces between molecules of the same substance

Question 16

Explain the structure of Crystalline Solids

Answer 16

Highly regular structures consisting of 3-dimensional systems of points called lattices, held together at their vertices by small, repeating units called Unit Cells

Question 17

What is the equation used for the x-ray analysis of solids?

Answer 17

nλ = 2d sin θ

Question 18

Explain the key point where Ionic, Molecular, and Atomic Solids deviate

Answer 18

Ionic: Ions are located at the lattice points
Molecular: Covalently bonded molecules are located at the lattice points
Atomic: Atoms are located at the lattice points

Question 19

Into which three subcategories can Atomic Solids be broken?

Answer 19

Metallic, Network, and Group 8A

Question 20

Explain Metallic Solids

Answer 20

Delocalized covalent bonding holds metal atoms together at the lattice points

Question 21

Explain Network Solids

Answer 21

Directional covalent bonding groups metal atoms into giant molecules, repeating 3-dimensional lattice structures

Question 22

Explain Group 8A Solids

Answer 22

LDFs hold group 8A atoms together at lattice points

Question 23

List some properties of metals

Answer 23

High thermal and electrical conductivity, malleability, ductility, high melting point

Question 24

Explain Closest Packing structure

Answer 24

Each atom has 12 closest neighbors: 6 in the same layer, 3 above, and 3 below

Question 25

Differentiate Hexagonal and Cubic Closest Packing

Answer 25

Hexagonal: aba - every other layer occupies the same vertical position Cubic: abba- every fourth layer occupies the same vertical position

Question 26

Describe Molecular Orbitals

Answer 26

Empty or partially filled valence electron orbitals of metal atoms through which electrons can flow

Question 27

How do MOs explain conductivity?

Answer 27

Bands of MOs exist in metals, which allow electrons to be quickly shuttled through many atoms, forming a sea of mobile electrons

Question 28

Describe an Alloy

Answer 28

A mixture of elements having overall metallic properties

Question 29

How do the two types of Alloys, Substitutional and Interstitial, vary?

Answer 29

Substitutional: some atoms of the host crystal are replaced by atoms of another substance Interstitial: small atoms of an added substance fit between the spaces of the host crystal

Question 30

Into what category of solids do Carbon and Silicon fall?

Answer 30

Network Atomic Solids

Question 31

What are the differences in structure between Diamond and Graphite?

Answer 31

Diamond: sp3 hybrid; Large energy gaps; No π bonds Graphite: sp2 hybrid; Small energy gaps; Connective π bonds

Question 32

Where do MO bands occur in Graphite?

Answer 32

Between sp2 hybridized layers, in the area where empty or partially filled π bonds interact

Question 33

What bonds typically occur in Silicon-based molecules?

Answer 33

Si-O bonds; σ bonds occur between Si and O atoms

Question 34

Describe Silicates

Answer 34

Polyatomic silicon-oxygen structures with metallic cations; often made of SiO4

Question 35

What two phases do ceramic structures exist in?

Answer 35

Minute crystals and cement

Question 36

Explain why Silicon is a Semiconductor

Answer 36

A few electrons can cross into MOs at standard temperature (298K) in Silicon

Question 37

Explain Contact Potential

Answer 37

A buildup of charge based on the reduction of electron movement

Question 38

Describe an n-type semiconductor

Answer 38

Adding a substance with more electrons that the host crystal to a mixture enables more electrons to be used for conduction through MOs

Question 39

What is the difference between p-type and n-type regions?

Answer 39

p-type: surplus of electrons | n-type: lack of electrons (holes)

Question 40

What reaction does adding like charge to a p-n junction produce? What is this called?

Answer 40

Both electrons and holes flow away from the like charge, moving away from the poles of charge, or Reverse Bias

Question 41

What reaction is produced by adding opposite charge to a p-n junction? What is this called?

Answer 41

Both holes and electrons flow toward the opposite poles, producing electrical current, or Forward Bias

Question 42

How does the term Rectifier correlate to p-n junctions?

Answer 42

p-n junctions create a pulsating current (one-directional) from opposing currents (multi-directional)