Chapter 14 Liquids and Solids Chapter 14 Table of Contents 14.1 14.2 14.3 14.4 14.5 14.6 Water and Its Phase Changes Energy Requirements for the Changes of State Intermolecular Forces Evaporation and.
Download ReportTranscript Chapter 14 Liquids and Solids Chapter 14 Table of Contents 14.1 14.2 14.3 14.4 14.5 14.6 Water and Its Phase Changes Energy Requirements for the Changes of State Intermolecular Forces Evaporation and.
Chapter 14
Liquids and Solids
Chapter 14 Table of Contents
14.1 Water and Its Phase Changes
14.2 Energy Requirements for the Changes of State
14.4 Evaporation and Vapor Pressure
14.5 The Solid State: Types of Solids
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Chapter 14
+ + Solid H Dipole-Dipole Forces H δ+ O δ H δ+ δ+ O δ H δ+ H δ+ O δ H δ+ Liquid Gas 3
Section 14.1
Water and Its Phase Changes
•
Reviewing What We Know
Gases Low density Highly compressible Fill container • Solids High density Slightly compressible Rigid (keeps its shape) Copyright © Cengage Learning. All rights reserved
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Section 14.1
Water and Its Phase Changes Heating/Cooling Curve
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Section 14.1
Water and Its Phase Changes 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
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Section 14.1
Water and Its Phase Changes Concept Check
During the process of melting ice by adding heat, the slurry temperature of the ice/liquid water a) stays constant.
b) increases.
c) decreases.
d) cannot be predicted.
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Section 14.2
Energy Requirements for the Changes of State
• Changes of state are physical changes. No chemical bonds are broken. • 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.
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Section 14.2
Energy Requirements for the Changes of State
• • Molar heat of fusion mol of a substance.
– energy required to melt 1 Molar heat of vaporization – energy required to change 1 mol of a liquid to its vapor.
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Section 14.2
Energy Requirements for the Changes of State Concept Check
Which would you predict to be larger given substance: H vap or H fus ?
for a Explain why.
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Section 14.2
Energy Requirements for the Changes of State 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.
o C.
a) 4.27 × 10 5 kJ b) 3.15 × 10 4 kJ c) 2.37 × 10 4 kJ d) 1.18 × 10 3 kJ 2 1000 g 1 kg 1 mol H O 2 18.016 g H O 2 40.6 kJ mol
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Section 14.2
Energy Requirements for the Changes of State Intramolecular Forces
• “Within” the molecule.
• Molecules are formed by sharing electrons between the atoms.
• Hold the atoms of a molecule together.
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Section 14.2
Energy Requirements for the Changes of State Intermolecular Forces
• Forces that occur between molecules.
• Intramolecular bonds are stronger than intermolecular forces.
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Section 14.2
Energy Requirements for the Changes of State Concept Check
Which are stronger , intramolecular bonds or intermolecular forces?
How do you know?
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Section 14.3
Intermolecular Forces
• Forces that occur between molecules.
Dipole –dipole forces Hydrogen bonding London dispersion forces
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Section 14.3
Intermolecular Forces Dipole –Dipole Attraction
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Section 14.3
Intermolecular Forces 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.
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Section 14.3
Intermolecular Forces Hydrogen Bonding
• Strong dipole-dipole forces.
• Hydrogen is bound to a highly electronegative atom – nitrogen, oxygen, or fluorine.
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Section 14.3
Intermolecular Forces Hydrogen Bonding in Water
• Blue dotted lines are the intermolecular forces between the water molecules.
Hydrogen Bonds hold DNA together.
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Section 14.3
Intermolecular Forces Hydrogen Bonding
• Affects physical properties Boiling point Melting point Copyright © Cengage Learning. All rights reserved
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Section 14.3
Intermolecular Forces
About 70% of our planet is covered by water. Perhaps we should call it not “earth” but “ocean”. Where did the water come from?
Section 14.3
Intermolecular Forces
Some say the water came from comets (mostly water) colliding with earth…Why did thy not collide with other planets that have no water??? Jupiter is 317 times the mass of the earth! Shoemaker-Levi colliding with Jupiter.
Section 14.3
Intermolecular Forces
Moon rocks have been found to be as old as 4.527 billion years while the oldest earth rock has been found to be 4.28 billion years old. Moon rocks have been found to be magnetic (when they cooled they were under a magnetic field caused by a rapidly rotating planet). The moon is not rotating rapidly now. The moon and the earth have not always been together!!!
Johnson Space Center Moon Rock Bldg.
Section 14.3
Intermolecular Forces London Dispersion Forces
• Instantaneous dipole that occurs accidentally when a given atom induces a similar dipole in a neighboring atom.
• Significant in large atoms/molecules.
• Occurs in
all molecules
, including nonpolar ones.
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Section 14.3
Intermolecular Forces London Dispersion Forces – Nonpolar Molecules
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Section 14.3
Intermolecular Forces London Dispersion Forces
• Become stronger as the sizes of atoms or molecules increase.
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Section 14.3
Intermolecular Forces Melting and Boiling Points
• In general, the stronger the intermolecular forces, the higher the melting and boiling points.
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Section 14.3
Intermolecular Forces Concept Check
Which molecule is capable of forming stronger intermolecular forces?
N 2 H 2 O Explain.
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Section 14.3
Intermolecular Forces Concept Check
Draw two Lewis structures for the formula C 2 H 6 O and compare two molecules. the boiling points of the H H C H H C H O H Copyright © Cengage Learning. All rights reserved H H C H O H C H H
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Section 14.3
Intermolecular Forces Concept Check
Which gas would behave more ideally same conditions of P and T?
at the CO or N 2 Why?
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Section 14.3
Intermolecular Forces Concept Check
Consider the following compounds: NH 3 CH 4 H 2 How many of the compounds above exhibit London dispersion forces ?
a) 0 b) 1 c) 2 d) 3 Copyright © Cengage Learning. All rights reserved
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Section 14.4
Evaporation and Vapor Pressure 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.
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Section 14.4
Evaporation and Vapor Pressure
• • •
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 Copyright © Cengage Learning. All rights reserved
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Section 14.4
Evaporation and Vapor Pressure 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.
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Section 14.4
Evaporation and Vapor Pressure Ilustration of Vapor Pressure
Who’s this?
Budda Water Budda (air pressure) will keep the liquid water down while the heat vaporizes the surface water.
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Section 14.4
Evaporation and Vapor Pressure Ilustration of Vapor Pressure
When the vapor pressure exceeds the air pressure, Budda cannot keep the liquid water down.
Water Then Budda rises and vapor bubbles form throughout the liquid. And it boils!
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Section 14.4
Evaporation and Vapor Pressure Concept Check
What is the vapor pressure of water at 100 °C? How do you know?
1 atm Copyright © Cengage Learning. All rights reserved
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Section 14.4
Evaporation and Vapor Pressure Vapor Pressure
• Liquids in which the intermolecular forces are strong have relatively low vapor pressures.
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Section 14.4
Evaporation and Vapor Pressure Concept Check
Which of the following would be expected to have the highest vapor pressure at room temperature?
a) CH 3 CH 2 CH 2 OH b) CH 3 CH 2 CH 2 NH 2 c) CH 3 CH 2 CH 2 CH 3 d) CH 3 CH 2 CH 3 Copyright © Cengage Learning. All rights reserved
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Section 14.5
The Solid State: Types of Solids Crystalline Solids
• Regular arrangement of their components.
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Section 14.5
The Solid State: Types of Solids Types of Crystalline Solids
Diamonds
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Section 14.5
The Solid State: Types of Solids
• • •
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.
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Section 14.5
The Solid State: Types of Solids Examples of Three Types of Crystalline Solids
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Section 14.6
Bonding in Solids Examples of the Various Types of Solids
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Section 14.6
Bonding in Solids Ionic Solids
• Stable substances with high melting points. • Held together by strong forces between ions.
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Section 14.6
Bonding in Solids Molecular Solids
• Fundamental particle is a molecule. • Melt at relatively low temperatures. • Held together by weak intermolecular forces. Copyright © Cengage Learning. All rights reserved
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Section 14.6
Bonding in Solids Atomic Solids
• Fundamental particle is the atom. • Properties vary greatly. Group 8 – low melting points Diamond – very high melting point
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Section 14.6
Bonding in Solids
Dr. Tacy Hall’s Artificial Diamond Presses Pictures to the left and below are of diamonds made from graphite. Dr. Hall made diamonds from peanut butter as well.
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Section 14.6
Bonding in Solids Bonding in Metals
• Metals are held together by nondirectional covalent bonds (called the electron sea model) among the closely packed atoms.
The word ICE made from Nitinol wire, stretched, reforms in warm water.
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Section 14.6
Bonding in Solids Bonding in Metals
• Metals form alloys of two types.
Substitutional – different atoms are substituted for the host metal atoms.
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Section 14.6
Bonding in Solids Bonding in Metals
• Metals form alloys of two types.
Interstitial – small atoms are introduced into the “holes” in the metallic structure.
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