3.3

Question 1

Surface tension

Answer 1

Amount of energy required to stretch or increase the surface of a liquid by a unit area

Question 2

Viscocity

Answer 2

A measure of a fluid’s resistance to flow

Question 3

Why is water able to form a three-dimensional structure?

Answer 3

Each oxygen atom can form two hydrogen bonds, allowing it to tetrahedrally bond to four hydrogen atoms (2 covalently, 2 by hydrogen bonds).

Question 4

Crystalline solid

Answer 4

Possesses rigid and long-range order. It’s atoms, molecules, or ions occupy specific positions.

Question 5

Amorphous solids

Answer 5

Lack well-defined arrangement and long-range molecular order.

Question 6

Unit cell

Answer 6

Basic repeating structural unit of a crystalline solid.

Question 7

Coordination number

Answer 7

The number of atoms or ions surrounding an atom or ion in a crystal lattice. It’s value gives a measure of how tightly the spheres are packed together.

Question 8

Body-centered cubic cell

Answer 8

The second layer of spheres fit into the depression of the first layer, and the third layer into the depressions of the second layer.
Coordination number of each sphere is 8.

Question 9

Face-centered cubic cell

Answer 9

Spheres at the center of each of the six faces of the cube, in addition to eight corner spheres.
Coordination number is 12

Question 10

How are atoms shared in all types of cubic cells?

Answer 10

Each corner atom belongs to eight unit cells; an edge atom is shared by four unit cells and a face-centered atom is shared by two unit cells.

Question 11

How many spheres are inside a simple cubic unit cells?

Answer 11

One

Question 12

How many complete spheres are in a body-centered cubic cells?

Answer 12

Two, one in the center and eight shared corner spheres.

Question 13

How many complete spheres are in a face-centered cubic cells?

Answer 13

Four - three from the six face-centered atoms and one from the eight shared corner spheres.

Question 14

Closest packing

Answer 14

The most efficient arrangement of spheres

Question 15

Hexagonal close packing structure

Answer 15

Each third layer sphere is directly over a first-layer sphere. (ABA).
There is no difference between the first and third layer arrangements, so the third layer is called A.

Question 16

Cubic close packing structure

Answer 16

The third layer spheres fit into the depressions that lie directly over the depressions in the first layer. The third layer is called c. (ABC)

Question 17

X-ray diffraction

Answer 17

Scattering of X rays by units of a crystalline solid, used to deduce the arrangement of particles in the solid lattice

Question 18

Electron-density contour map

Answer 18

Relative electron densities at various locations in a crystal

Question 19

At any given temperature, the rate of evaporation is ____, and the rate of condensation…

Answer 19

constant
increases with the increasing concentration of molecules in the vapor phase

Question 20

Dynamic equilibrium

Answer 20

The rate of a forward process is balanced by the rate of the reverse process

Question 21

Equilibrium vapor pressure

Answer 21

Vapor pressure measured when a dynamic equilibrium exists between condensation and vaporization

Question 22

Two important characteristics of equilibrium vapor pressure

Answer 22

(1) Maximum vapor pressure of a liquid at a given temperature
(2) Constant at a constant temperature, independent of the amount of a liquid

Question 23

Molar heat of vaporization (ΔHvap)

Answer 23

A measure of the strength of intermolecular forces in a liquid, the energy required to vaporize one mole of a liquid

Question 24

Clausius-Clapeyron equation

Answer 24

ln P = -ΔHvap/RT + C
ln(P1/P2) = ΔHvap/R * (T1 - T2)/(T1T2)

Question 25

Boiling point

Answer 25

Temperature at which the vapor pressure of a liquid is equal to the external pressure

Question 26

Critical temperature (Tc)

Answer 26

A temperature above which a substance’s gas phase cannot be made to liquefy, no matter the applied pressure.
Above this temperature there is no distinction between a liquid and a gas (just a fluid)

Question 27

Critical pressure (Pc)

Answer 27

Minimum pressure that must be applied to bring about liquefaction at the critical temperature

Question 28

Melting point of a solid or freezing point of a liquid

Answer 28

Temperature at which solid and liquid phases coexist in equilibrium

Question 29

Molecular heat of fusion (ΔHfus)

Answer 29

Energy required to melt 1 mole of a solid

Question 30

Why is ΔHfus smaller than ΔHvap?

Answer 30

Molecules in a liquid are fairly closely packed, so some energy is required to bring about the rearrangement from solid to liquid.
When a liquid evaporates, molecules are completely separated and a considerably greater amount of energy is required to overcome the attractive force.

Question 31

Sublimation

Answer 31

Process in which molecules go directly from solid into vapor phase

Question 32

Deposition

Answer 32

Molecules make the transition from vapor to solid directly

Question 33

Molar heat of sublimation (ΔHsub)

Answer 33

Energy required to sublime 1 mole of a solid
ΔHsub = ΔHfus + ΔHvap