Download Ch 11a Outline

Dr. Pérez
CHM1046C - Chapter 11a
pg 1 of 12
This number corresponds to the slide number on the top right corner of PowerPoint
(1) CH. 11 Intermolecular Forces, Liquids and Solids
Objectives
 Determine intermolecular forces of covalent compounds and atoms
 Predict properties of liquids
 Understand/calculate Vapor Pressure
 Understand boiling and freezing points
 Understand/calculate heat involved in phase changes
 Understand Phase Diagrams, recognize components
 Know types of crystalline Solids
 Predict properties of solids
(Note: We will skip sections 11.10, 11.11, 11.13)
(2) GOAL (11.2): Understand and determine the type of intermolecular force present
(3) Boiling Points of Selected Compounds
M.M. (g/mol)
Bp (oC)
Butane CH3CH2CH2CH3
58.1
-0.5
Pentane CH3CH2CH2CH2CH3
72.2
36.1
Hexane CH3CH2CH2CH2CH2CH3
86.2
69
58.1
56.2
Alkanes and Ketones
Acetone
O
CH3CCH3
O
2-pentanone
86.1
102
CH3CH2CH2CCH3
O
2-hexanone
100
128
CH3CH2CH2CH2CCH3
Compare the boiling point of two compounds of roughly the same molar mass. Propose a
hypothesis that explains the cause of the observations.
Dr. Pérez
CHM1046C - Chapter 11a
(4) Dipole-Dipole Forces
 Occurs when ________ molecules interact.
 Stronger Strength of Attraction
_____ Polarity
 Stronger Strength of Attraction
_____ Distance
Draw a picture that illustrates this force:
(5) London Dispersion Forces
 Due to motion of ____________
 Causes ____________ dipole:
Polarizability
 Present in all uncombined atoms, polar and non-polar molecules
pg 2 of 12
Dr. Pérez
CHM1046C - Chapter 11a
pg 3 of 12
(6) STRENGTH OF London Dispersion Forces DEPENDS ON:
(1) Molecules:
 The greater the number of places on molecule (chain), the ____________ the
strength of attraction to other molecules of the same type.
 Long, skinny molecules tend to have ____________ dispersion forces than short,
fat ones.
(2) Uncombined atoms:
 The more ____________, the greater the chances for distortion of the electron cloud
(polarizability), and thus the ____________ the strength of attraction to other
molecules of the same type.
(7) Which of the following two hydrocarbons would have the greater boiling point?
A. Propane (C3H8)
B. Hexane (C6H14)
(8) Read the answers you recorded on slide 4. Answer and complete table.
Alkanes and Ketones
M.M. (g/mol)
Bp (oC)
Butane CH3CH2CH2CH3
58.1
-0.5
Pentane CH3CH2CH2CH2CH3
72.2
36.1
Hexane CH3CH2CH2CH2CH2CH3
86.2
69
Acetone
58.1
56.2
86.1
102
100
128
O
CH3CCH3
2-pentanone
O
CH3CH2CH2CCH3
2-hexanone
O
CH3CH2CH2CH2CCH3
Type of
Covalent
Compound
Intermolecular
Force
Dr. Pérez
CHM1046C - Chapter 11a
pg 4 of 12
(9) More Boiling Points
Alcohols
M.M. (g/mol)
Bp (oC)
1-propanol CH3CH2CH2OH
60.1
97.4
1-butanol CH3CH2CH2CH2OH
74.1
117
1-pentanol CH3CH2CH2CH2CH2OH
86.2
137
1-hexanol CH3CH2CH2CH2CH2CH2OH
102
158
The data from slide 8 was plotted in the graph below.
•
•
•
Data for alkanes and ketones from slide 9 are graphed below. Draw a smooth line to show
their trends.
Plot the alcohols on the graph. Add a smooth trend line.
Propose an explanation for the observations.
Boiling Points of Selected Compounds
160
140
Alkanes
120
Ketones
100
Boiling
Point
o
( C)
Alcohols
80
60
40
20
0
-20
0
20
40
60
Molar Mass (g/mol)
80
100
120
Dr. Pérez
CHM1046C - Chapter 11a
pg 5 of 12
(10) Hydrogen Bonding
 A ________ ________ dipole-dipole force due to
 The small size of the elements enables the  + to closely approach the  - creating
a very strong dipole.
 The relatively large ________ difference leads to especially polar bonds.
 The H of an N–H, O–H, or F–H group is strongly attracted to the ________ pair electrons
of an O, N, or F of ________ molecule
(11) The Boiling Points of the Covalent Hydrides of Elements
ce Hall, 2001.
(12) Ion-Dipole Forces
 Present in ________ of ________.
 The strength of these forces are
what make it possible for ________
substances to dissolve in ________ solvents.
 Stronger Strength of Attraction
_____ Polarity
 Stronger Strength of Attraction
_____ Ion Size
Dr. Pérez
CHM1046C - Chapter 11a
pg 6 of 12
(13) Forces
 Intramolecular:
–
Attractions between atoms _________ a molecule (=_________)
–
Determines ___________ properties
–
Approximate energy 100 – 1000 kJ/mol
 Intermolecular:
–
Attractions that occur _____________ particles (atoms or molecules).
–
Determines ____________ properties
–
Approximate energy 1 – 50 kJ/mol
Type
Strength
Occurs between
Ion – Dipole
Moderate:10-50 kJ/mol
Hydrogen Bonding
Moderate:10-40 kJ/mol
Dipole-Dipole
Weak 3-4 kJ/mol
London Dispersion
Weak 1-10 kJ/mol
Collectively referred to as van der Waals forces. Present ONLY in ________ ________
Compounds
(14) Practice: What type of intermolecular attractive forces are present in the following
substances?
Substance
NH3
PH3
BH3
KBr(aq)
Structure
Ion-
Dipole-
Hydrogen London
Dipole?
Dipole?
Bonding?
Forces?
Dr. Pérez
CHM1046C - Chapter 11a
pg 7 of 12
(15) Quiz
Substance
Structure
IonDipole?
DipoleDipole?
Hydrogen London
Bonding? Forces?
H2 S
Kr
SF4
Assignment: EOCE (end-of-chapter excercises): 11.49, 11.51
(16) GOALS (11.4)
 Define the following properties of liquids, and relate these properties to the intermolecular
forces involved:





Surface Tension
Capillary Action
Viscosity
Phase changes
Vapor Pressure
(17) 11.4 PROPERTIES OF LIQUIDS: VISCOSITY
 A measure of the liquid’s ____________ to flow.
 ↑intermolecular force ____viscosity
 The longer the molecule the ____ viscosity.
 ↑ temperature ____ viscosity.
 The more spherical the molecular shape, the ____ viscosity
Dr. Pérez
CHM1046C - Chapter 11a
pg 8 of 12
(18) PROPERTIES OF LIQUIDS: SURFACE TENSION
 Resistance of a liquid to increase in ____________ ____________.
–
Caused by the net ____________ force experienced by the molecules on the surface
of a liquid.
–
Shape with smallest surface area - ____________
 ↑intermolecular force ____ surface tension
 ↑ temperature ____ surface tension
(19) PROPERTIES OF LIQUIDS: CAPILLARY ACTION
 The ____________ rising of a liquid in a narrow tube.
Exercise: Draw graduated cylinder and meniscus for:
Concave:
CF ___AF
Convex:
CF ___AF
 Two forces involved:
 Cohesive forces (CF) hold the liquid molecules together.
 Adhesive forces (AF) attract the outer liquid molecules to the tube’s surface.
(20) 11.2 Changes in Physical State
Tro, “Chemistry”,
3rd ed. Pearson,
2014.
Dr. Pérez
CHM1046C - Chapter 11a
pg 9 of 12
(21) Some Phase Changes
 Boiling point (Tb) – The ____ at which the liquid’s ______ _______ equals the _____
_____ .
–
Normal boiling point – boils at _____.
–
↑atmospheric pressure ___Tb
–
↑ Intermolecular force ____ Tb
 Freezing point - the _____ at which a pure ________ changes to a ________ ______.
 Melting point - the ________ at which a ________ becomes a ________ .
–
identical to the freezing point
–
↑atmospheric pressure ________ Tf /Tm
–
↑ Intermolecular force __________ Tf /Tm Ex. __________
(23) PROPERTIES OF LIQUIDS: EVAPORATION
 Molecules in the liquid are constantly in ____________.
 The average kinetic energy is proportional to the temperature.
Fig. 11.4 Tro, “Chemistry”, 3rd ed. Pearson, 2014
 Vaporization – process by which ___________ energy can overcome intermolecular forces
producing phase change from liquid to gas
 Rate of evaporation is dependent on:
–
The strengths of intermolecular force : ↑ intermolecular force _______ rate
–
The temperature: ↑ T _____ Ek _____ rate
–
The surface area: ↑ surface area _____ rate
 Volatile - ___________________________________________________________
Dr. Pérez
CHM1046C - Chapter 11a
pg 10 of 12
(24) 1. Greater intermolecular force:
A. NF3
B. PF3
(25) 2. Highest boiling point:
A. CBr4
B. CF4
C. CI4
(26) 3. Lowest freezing point:
A. NaBr
B. N2
C. HCl
(27) 4. Lowest vapor pressure at 25oC
A. CH3CH2OCH2CH3
B. CH3CH2CH2CH2OH
C. CH3CH2CH2CH3
(28) 5.Greatest a viscosity:
A. H2S
B. H2O2
C. SiH4
(29) 6. Lower melting point:
A. Left
B. Right
Assignment: EOCE Assignment: EOCE 11.53, 11.55, 11.57, 11.59, 11.61, 11.63, 11.65, 11.67,
11.69
Dr. Pérez
CHM1046C - Chapter 11a
pg 11 of 12
(30) GOAL: Calculate the heat change involved over a range of temperatures (section 11.7)
(31) Energy Changes Associated with Changes of State
Fig. 11.36: Heating curve for water. Tro, “Chemistry”, 3rd ed. Pearson, 2014
(32) Heat of Phase Transition
 Heat of vaporization ( Hovap)- The amount of energy required to vaporize 1 mole of a
substance (measured at 1 atm & the temperature of the change).
 Heat of fusion ( Hofus)- The amount of energy required to melt 1 mole of a substance
(measured at 1 atm & the temperature of the change).
 Heat of sublimation ( Hosub)- The amount of energy required to sublime 1 mole of a
substance (measured at 1 atm & the temperature of the change).
(33) Quantitative Aspects of Phase Changes
The total enthalpy change is the __________of the changes of the individual steps.
-
Calculating the enthalpy during the change in temperature within a phase (Chapter 6):
-
Calculating the enthalpy of a phase change:
Note: You need to assign the  Hphase change sign.
Dr. Pérez
CHM1046C - Chapter 11a
pg 12 of 12
(34) Problem 1 Calculate Energy
 How much energy does it take to convert 1.000 kg of steam at 300.0 oC ice at – 32.0 oC?
 The specific heat capacities of H2O are:
ice, 2.1 J/g· oC
liquid, 4.2 J/g· oC
steam, 2.0 J/g· oC
 For H2O, Δ Hvap = 40.67 kJ/mol and Δ Hfus = 6.01 kJ/mol.
 Assignment: 11.79, 11.83, 11.127, 11.154
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