Chapter 14 Liquids and Solids. Chapter 14 Table of Contents Copyright © Cengage Learning. All...
-
Upload
eleanore-victoria-gray -
Category
Documents
-
view
224 -
download
0
Transcript of Chapter 14 Liquids and Solids. Chapter 14 Table of Contents Copyright © Cengage Learning. All...
Chapter 14
Liquids and Solids
Chapter 14
Table of Contents
Copyright © Cengage Learning. All rights reserved 2
14.1 Water and Its Phase Changes
14.2 Energy Requirements for the Changes of State
14.3 Intermolecular Forces
14.4 Evaporation and Vapor Pressure
14.5 The Solid State: Types of Solids
14.6 Bonding in Solids
Section 14.1
Water and Its Phase Changes
Return to TOC
Copyright © Cengage Learning. All rights reserved 3
Reviewing What We Know
• Gases Low density Highly compressible Fill container
• Solids High density Slightly compressible Rigid (keeps its shape)
Section 14.1
Water and Its Phase Changes
Return to TOC
Copyright © Cengage Learning. All rights reserved 4
Heating/Cooling Curve
Section 14.1
Water and Its Phase Changes
Return to TOC
Copyright © Cengage Learning. All rights reserved 5
Heating/Cooling Curve
• Normal boiling point: at 1 atm = 100°C • Normal freezing point: at 1 atm = 0°C • Density
Liquid water = 1.00 g/mL Ice = 0.917 g/mL
Section 14.1
Water and Its Phase Changes
Return to TOC
Copyright © Cengage Learning. All rights reserved 6
Concept Check
During the process of melting ice by adding heat, the temperature of the ice/liquid water slurry
a) stays constant.b) increases.c) decreases.d) cannot be predicted.
Energy Requirements for the Changes of State
Section 14.2
Return to TOC
Copyright © Cengage Learning. All rights reserved 7
• Changes of state are physical changes. No chemical bonds
are broken.
Energy Requirements for the Changes of State
Section 14.2
Return to TOC
Copyright © Cengage Learning. All rights reserved 8
Phase Changes
• When a substance changes from solid to liquid to gas, the molecules remain intact.
• The changes in state are due to changes in the forces among molecules rather than in those within the molecules.
Energy Requirements for the Changes of State
Section 14.2
Return to TOC
Copyright © Cengage Learning. All rights reserved 9
Phase Changes
• Solid to Liquid As energy is added, the motions of the
molecules increase, and they eventually achieve the greater movement and disorder characteristic of a liquid.
• Liquid to Gas As more energy is added, the gaseous state
is eventually reached, with the individual molecules far apart and interacting relatively little.
Energy Requirements for the Changes of State
Section 14.2
Return to TOC
Copyright © Cengage Learning. All rights reserved 10
Intramolecular Forces
• “Within” the molecule.• Molecules are formed by sharing electrons
between the atoms.• Hold the atoms of a molecule together.
Energy Requirements for the Changes of State
Section 14.2
Return to TOC
Copyright © Cengage Learning. All rights reserved 11
Intermolecular Forces
• Forces that occur between molecules.
• Intramolecular bonds are stronger than intermolecular forces.
Energy Requirements for the Changes of State
Section 14.2
Return to TOC
Copyright © Cengage Learning. All rights reserved 12
• Molar heat of fusion – energy required to melt 1 mol of a substance.
• Molar heat of vaporization – energy required to change 1 mol of a liquid to its vapor.
Energy Requirements for the Changes of State
Section 14.2
Return to TOC
Copyright © Cengage Learning. All rights reserved 13
Concept Check
Which are stronger, intramolecular bonds or intermolecular forces?
How do you know?
Energy Requirements for the Changes of State
Section 14.2
Return to TOC
Copyright © Cengage Learning. All rights reserved 14
Concept Check
Which would you predict should be larger for a given substance: Hvap or Hfus?
Explain why.
Energy Requirements for the Changes of State
Section 14.2
Return to TOC
Copyright © Cengage Learning. All rights reserved 15
Concept Check
The unusually high value of the molar heat of vaporization of water (40.6 kJ/mole) is an important factor in moderating the temperature of the earth’s surface, and results in an enormous transfer of energy to the atmosphere as liquid water evaporates as part of the hydrologic cycle. Calculate the amount of heat in kJ needed to evaporate 10.5 kg of liquid water at 100.oC.
a) 4.27 × 105 kJb) 3.15 × 104 kJc) 2.37 × 104 kJd) 1.18 × 103 kJ
422
2
1 mol H O1000 g 40.6 kJ10.5 kg H O 2.37 10 kJ
1 kg 18.016 g H O mol
Intermolecular Forces
Section 14.3
Return to TOC
Copyright © Cengage Learning. All rights reserved 16
• Forces that occur between molecules. Dipole–dipole forces
Hydrogen bonding London dispersion forces
Intermolecular Forces
Section 14.3
Return to TOC
Copyright © Cengage Learning. All rights reserved 17
Dipole–Dipole Attraction
Intermolecular Forces
Section 14.3
Return to TOC
Copyright © Cengage Learning. All rights reserved 18
Dipole-Dipole Forces
• Dipole moment – molecules with polar bonds often behave in an electric field as if they had a center of positive charge and a center of negative charge.
• Molecules with dipole moments can attract each other electrostatically. They line up so that the positive and negative ends are close to each other.
• Only about 1% as strong as covalent or ionic bonds.
Intermolecular Forces
Section 14.3
Return to TOC
Copyright © Cengage Learning. All rights reserved 19
Hydrogen Bonding
• Strong dipole-dipole forces.• Hydrogen is bound to a highly electronegative
atom – nitrogen, oxygen, or fluorine.
Intermolecular Forces
Section 14.3
Return to TOC
Copyright © Cengage Learning. All rights reserved 20
Hydrogen Bonding in Water
• Blue dotted lines are the intermolecular forces between the water molecules.
Intermolecular Forces
Section 14.3
Return to TOC
Copyright © Cengage Learning. All rights reserved 21
Hydrogen Bonding
• Affects physical properties Boiling point
Intermolecular Forces
Section 14.3
Return to TOC
Copyright © Cengage Learning. All rights reserved 22
London Dispersion Forces
• Instantaneous dipole that occurs accidentally in a given atom induces a similar dipole in a neighboring atom.
• Significant in large atoms/molecules.• Occurs in all molecules, including nonpolar
ones.
Intermolecular Forces
Section 14.3
Return to TOC
Copyright © Cengage Learning. All rights reserved 23
London Dispersion Forces – Nonpolar Molecules
Intermolecular Forces
Section 14.3
Return to TOC
Copyright © Cengage Learning. All rights reserved 24
London Dispersion Forces
• Become stronger as the sizes of atoms or molecules increase.
Intermolecular Forces
Section 14.3
Return to TOC
Copyright © Cengage Learning. All rights reserved 25
Melting and Boiling Points
• In general, the stronger the intermolecular forces, the higher the melting and boiling points.
Intermolecular Forces
Section 14.3
Return to TOC
Copyright © Cengage Learning. All rights reserved 26
Concept Check
Which molecule is capable of forming stronger intermolecular forces?
N2 H2O
Explain.
Intermolecular Forces
Section 14.3
Return to TOC
Copyright © Cengage Learning. All rights reserved 27
Concept Check
Draw two Lewis structures for the formula C2H6O and compare the boiling points of the two molecules.
C
H
H C
H
H
H
O H C
H
H C
H
H
H
O H
Intermolecular Forces
Section 14.3
Return to TOC
Copyright © Cengage Learning. All rights reserved 28
Concept Check
Which gas would behave more ideally at the same conditions of P and T?
CO or N2
Why?
Intermolecular Forces
Section 14.3
Return to TOC
Copyright © Cengage Learning. All rights reserved 29
Concept Check
Consider the following compounds:
NH3 CH4 H2
How many of the compounds above exhibit London dispersion forces?
a) 0
b) 1
c) 2
d) 3
Section 14.4
Evaporation and Vapor Pressure
Return to TOC
Copyright © Cengage Learning. All rights reserved 30
Vaporization or Evaporation
• Molecules of a liquid can escape the liquid’s surface and form a gas.
• Endothermic process – requires energy to overcome the relatively strong intermolecular forces in the liquid.
Section 14.4
Evaporation and Vapor Pressure
Return to TOC
Copyright © Cengage Learning. All rights reserved 31
Vapor Pressure
• Amount of liquid first decreases then becomes constant. • Condensation - process by which vapor molecules
convert to a liquid. • When no further change is visible the opposing
processes balance each other – equilibrium
Section 14.4
Evaporation and Vapor Pressure
Return to TOC
Copyright © Cengage Learning. All rights reserved 32
Vapor Pressure
• Pressure of the vapor present at equilibrium.• The system is at equilibrium when no net
change occurs in the amount of liquid or vapor because the two opposite processes exactly balance each other.
Section 14.4
Evaporation and Vapor Pressure
Return to TOC
Copyright © Cengage Learning. All rights reserved 33
Concept Check
What is the vapor pressure of water at 100°C? How do you know?
1 atm
Section 14.4
Evaporation and Vapor Pressure
Return to TOC
Copyright © Cengage Learning. All rights reserved 34
Vapor Pressure
• Liquids in which the intermolecular forces are strong have relatively low vapor pressures.
Section 14.4
Evaporation and Vapor Pressure
Return to TOC
Copyright © Cengage Learning. All rights reserved 35
Concept Check
Which of the following would be expected to have the highest vapor pressure at room temperature?
a) CH3CH2CH2OHb) CH3CH2CH2NH2
c) CH3CH2CH2CH3
d) CH3CH2CH3
Section 14.5
The Solid State: Types of Solids
Return to TOC
Copyright © Cengage Learning. All rights reserved 36
Crystalline Solids
• Regular arrangement of their components.
Section 14.5
The Solid State: Types of Solids
Return to TOC
Copyright © Cengage Learning. All rights reserved 37
Types of Crystalline Solids
Section 14.5
The Solid State: Types of Solids
Return to TOC
Copyright © Cengage Learning. All rights reserved 38
Types of Crystalline Solids
• Ionic Solids – ions at the points of the lattice that describes the structure of the solid.
• Molecular Solids – discrete covalently bonded molecules at each of its lattice points.
• Atomic Solids – atoms at the lattice points that describe the structure of the solid.
Section 14.5
The Solid State: Types of Solids
Return to TOC
Copyright © Cengage Learning. All rights reserved 39
Examples of Three Types of Crystalline Solids
Section 14.6
Bonding in Solids
Return to TOC
Copyright © Cengage Learning. All rights reserved 40
Examples of the Various Types of Solids
Section 14.6
Bonding in Solids
Return to TOC
Copyright © Cengage Learning. All rights reserved 41
Ionic Solids
• Stable substances with high melting points. • Held together by strong forces between ions.
Section 14.6
Bonding in Solids
Return to TOC
Copyright © Cengage Learning. All rights reserved 42
Molecular Solids
• Fundamental particle is a molecule. • Melt at relatively low temperatures. • Held together by weak intermolecular forces.
Section 14.6
Bonding in Solids
Return to TOC
Copyright © Cengage Learning. All rights reserved 43
Atomic Solids
• Fundamental particle is the atom. • Properties vary greatly.
Group 8 – low melting points Diamond – very high melting point
Section 14.6
Bonding in Solids
Return to TOC
Copyright © Cengage Learning. All rights reserved 44
Bonding in Metals
• Metals are held together by nondirectional covalent bonds (called the electron sea model) among the closely packed atoms.
Section 14.6
Bonding in Solids
Return to TOC
Copyright © Cengage Learning. All rights reserved 45
Bonding in Metals
• Metals form alloys of two types. Substitutional – different atoms are substituted for
the host metal atoms.
Section 14.6
Bonding in Solids
Return to TOC
Copyright © Cengage Learning. All rights reserved 46
Bonding in Metals
• Metals form alloys of two types. Interstitial – small atoms are introduced into the
“holes” in the metallic structure.
Section 14.6
Bonding in Solids
Return to TOC
Copyright © Cengage Learning. All rights reserved 47Copyright © Cengage Learning. All rights reserved 47
Homework
• Reading assignment– Pages 447 through 467
• Homework Problems– Questions and problems 9, 11, 21, 23, 27, 29, 33, 37,
45, 49.
• Due on
Chapter 14 Homework