Chapter 16 Liquids and Solids

Question 1

Surface tension (y)

Answer 1

Resistance of the surface of a liquid to an external force because of the attractive forces between molecules. Because of this it resists any increase to its surface area.

Question 2

Surface tension relasonships

Answer 2

Surface tension decreases with increasing temp because higher temp means greater KE

Question 3

Relasonship between KE and attractive forces

Answer 3

Greater KE = movement of molecules which decreases the pontential for attractive forces between molecules.
Lower attractive forces —-> surface tension will decrease

Question 4

Cohesive Forces

Answer 4

Forces between like molecules. Water droplet will stay intact on top of a surface. This phenomenon is observed with water droplets on a recently waxed car.

Question 5

Adhesive Forces

Answer 5

Forces between unlike molecules. A water droplet will spread out over a surface because the water molecules prefer the surface over each other

Question 6

Viscosity

Answer 6

Resistance to flow of a liquid and is a result of cohesive forces.
- As temp increases viscosity decreases because of higher kinetic energy
- Large complicated molecules tend to be more viscous because they become entangled more easily.

Question 7

Vapor Pressure(vp)

Answer 7

Every liquid will have a partial pressure of the gas directly above the liquid, which is called a vapor pressure(vp). Every liquid will have a vapor pressure which will be low. Less than atmospheric pressure

Question 8

Energy of Evaporation as Hvap, or enthalpy of vaporization.

Answer 8

• change in H vap is an endothermic process which is greater than zero.
  Change in H vap = H vap - Hliq >0

Heat is absorbed and enters system

Question 9

Enthalpy of condensation (Hcond) is less than zero.

Answer 9

Heat is being released by the process in order to allow condensation from gas to liquid state.

Change in Hcond = Hliq - Hvap = - Hvap <0

Question 10

Vapor Pressure relationships

Answer 10

As temperature increases will the vapor pressure,
Vapor pressure = atmospheric pressure, the liquid will begin to boil = boiling point
Stronger forces = lower vapor pressures

Question 11

Tips to remember with gas pressure relation

Answer 11

Density of the gas increases as density of liquid decreases
- Surface tension between the phases will approach zero and the interface will disappear
- The density of liquid = gas + surface tension = 0
Substance reached its critical temp and critical pressure = Critical point

Question 12

Clausius Clapeyron equation

Answer 12

Ln P2/P1 = Hvap / R (1/T1 - 1/T2)

Question 13

Constants

Answer 13

8.314 J/mol K
- Temperature must be in Kelvin
- Pressure can be any units as long as they are consistent
- Change in H vap can be found in tables given in Kj/mol. All units must be converted to J.
Normal boiling point P =1atm. T= 373K and P = 1atm

Question 14

Ideal gas law

Answer 14

N = PV/RT

Question 15

What causes states to change

Answer 15

Deposition: G ——> S
Sublimation S—-> G
Freezing: Liquid —-> solid
Melting : solid —-> liquid
Vaporization: liquid —-> gas
Condensation gas—-> liquid

Question 16

Sublimination formula

Answer 16

Change in Sublimination = change in H fusion + change in H vaporization

Question 17

Deposition formula

Answer 17

• Change in H deposition = H vaporization + change in H fusion

Question 18

Graph order of Physical states Least temp to greater temp

Answer 18

Solid, melting, liquid, boiling, vapor
-With time and increase in temp the physical states change

Question 19

Isobar

Answer 19

Phase diagram is a line at constant pressue

Question 20

Isotherm

Answer 20

On the phase diagram is a line at constant temp

Question 21

Real gas equation

Answer 21

(P + n^2a/(V^2)) (V-nb) = nRT

Question 22

Intramolecular forces

Answer 22

• Ionic
• Covalent
• Metallic

Question 23

Energy or strength of intramolecular forces (Kj/mol)

Answer 23

Ionic: (400-4000)
Covalent ( 150-1100)
Metallic (75-1000)

Question 24

Intermolecular forces

Answer 24

Ion Dipole
H-Bon
Dipole-Dipole
Ion-induced dipole
Dipole-induced Dipole
Dispersion(London)

Question 25

Energy or Strength (kJ/mol )

Answer 25

Ion-Dipole: 40-600
H-Bond: 10-40
Dipole-Dipole: 5-25
Ion-induced Dipole: 3-15
Dipole-Induced Dipole 2-10
Dispersion(London): 0.05-40

Question 26

Instaneous dipole

Answer 26

Created in the molecule with a partially negative charge and a partially positive charge. Points from positive to negative.

Question 27

London force release ship with molar mass of a molecule

Answer 27

London force will also increase as molar mass of a molecule increases.

Question 28

Polarizability

Answer 28

Is the ability for an atom or molecule to form instanous dipoles and it increases as volumes occupied by electrons increases.

Question 29

Hydrogen-bonding (H-bonding)

Answer 29

A third common intermolecular force, which is a very strong dipole force that earned it a category of its own.

Question 30

H-bonding occurs when

Answer 30

H atom is directly bonded to an electronegative element (usually an N,O, or F atom) forming a very strong dipole
0 H-bond actually occurs between the of one molecule and electronegative element of the other.

Question 31

How do identify the dominant force present.

Answer 31

If yes, the dominant force is ionic
If no, ask if there is an H atom with either an N, O, or F atom.
i. Yes the dominant force is H-bonding
ii. If no, ask if the molecule is asymmetric?
1. If yeast the dominant force is dipole
2. If no, the dominant force is London

Question 32

Strengths of intermolecular forces ranked greater to weak

Answer 32

Ionic(Strongest)
H-bond
Dipole
London (weakest, but increase as the molecule increases in size

Question 33

If the force is high then all the following are true

Answer 33

Viscosity is high
Surface tension is high
Boiling point (bp) is high
Vapor pressure (vp) is low
Enthalpy of vaporization (Change in H vaporization) is high.

Question 34

Five different unit cells along with characteristics

Answer 34

Location of Atom in Unit Cell
Corner
Edge
Face
Center
Number of Atoms in Unit Cell
1/8
1/4
1/2
1

Question 35

5 types of crystal structures you need to know

Answer 35

Simple cubic :
Body-centered cubic (bcc)
Face-centered cubic (fcc)
Hexagonal-close packed (hcp)
Cubic close packed (ccp)

Question 36

Density formula

Answer 36

D=m/v

Question 37

Mass equation

Answer 37

M= (atoms/unit cell) ( mol/6.022e^23 atoms) (grams/mol) = (atoms/unit cell) (Molar Mass/NA)

Question 38

Common conversions of length

Answer 38

1m =10^10 A
1m= 100cm
1m =10^9
1m = 10^12

Question 39

Bragg’s Law

Answer 39

N( wavelength) = 2d sin theta
D: is the distance between atom or diffracting planes
Wavelength of the x ray
Theta is the incident angle of the X-rays
N is an integer usually 1

Question 40

Boiling point definition