Liquids, Solids, and Materials

1
Chapter 11

• Liquids, Solids, and Materials

2
Overview

• The liquid state
• Vapor pressure
• Phase changes Solids, Liquids, Gases
• Water An Important Liquid with unusual
  properties
• Types of solids
• Crystalline solids
• Network solids
• Materials Science
• Metals, Semiconductors, and Insulators

3
Review States of Matter

• States of Matter

State
Shape and Volume
Compressibility
Ability to Flow
Gas
Conforms to shape and volume of container
high
high
Liquid
Conforms to shape of container volume limited by
surface
very low
moderate
Solid
Maintains its own shape and volume
almost none
almost none
4
Review Intramolecular forces

• College Chemistry I
• Ionic Compounds
• comprised of positive and negative charged ions
• The intermolecular force is great due to forming
  a lattice among the ions hence high boiling and
  melting points
• Covalent compounds
• Comprised of atoms attracted to each other so
  that each atom achieves an octet
• The covalent bond itself is extremely strong
• Intermolecular forces are not strong

5
Review - Intermolecular Forces
6
The Liquid State

• Most liquids are substances whose condensation
  temperatures are above room temperature
• Condensation - point at which a gas forms a
  liquid
• Occurs because the gas molecules no longer posses
  the energy to overcome intermolecular forces

7
The Liquid State

• Property
• Viscosity ability to flow
• Stronger the force lower the viscosity
• Viscosity is increased as temperature increases
• Surface Tension ability to expand a liquid
  surface
• Surface Tension increases with increased
  intermolecular forces

8
Problems

• Which of the following factors contributes to a
  low viscosity for a liquid?
• A)low temperature
• B)spherical molecular shape
• C)hydrogen bonding
• D)high molecular weight
• E)high boiling point

9
Problems

• Which of the following should have the highest
  surface tension at a given temperature?
• A)
• B)
• C)
• D)
• E)

10
The Liquid State

• Properties
• Capillary Action
• Meniscus

11
Problems

• When the adhesive forces between a liquid and the
  walls of a capillary tube are greater than the
  cohesive forces within the liquid
• A)the liquid level in a capillary tube will rise
  above the surrounding liquid and the surface in
  the capillary tube will have a convex meniscus.
• B)the liquid level in a capillary tube will rise
  above the surrounding liquid and the surface in
  the capillary tube will have a concave meniscus.
• C)the liquid level in a capillary tube will drop
  below the surrounding liquid and the surface in
  the capillary tube will have a convex meniscus.
• D)the liquid level in a capillary tube will drop
  below the surrounding liquid and the surface in
  the capillary tube will have a concave meniscus.
• E)none of the above will occur.

12
Vapor Pressure

• Volatility of a liquid is the tendency of the
  liquid to vaporize
• Increases with increase in temperature

13
Vapor Pressure

• Vapor pressure point at which a dynamic
  equilibrium occurs the rate at which a liquid
  turns into a gas is the same as the rate when a
  gas turns into a liquid
• Increased intermolecular forces increase the
  temperature where the dynamic equilibrium occurs

14
Problems

• Select the pair of substances in which the one
  with the higher vapor pressure at a given
  temperature is listed first.
• A)C7H16, C5H12
• B)CCl4, CBr4
• C)H2O, H2S
• D)CH3CH2OH, CH3OCH3
• E)Xe, Kr

15
Vapor Pressure

• When the vapor pressure in an open container
  equals the atmospheric pressure bubbles rise
  and the liquid reaches its boiling point.
• At atmospheric pressure of 1 atm normal boiling
  point

16
Vapor Pressure

• Clausius- Clapeyron Equation Relates vapor
  pressure and temperature

17
Vapor Pressure

• Clausius- Clapeyron Equation

18
Problems

• Octane has a vapor pressure of 40. torr at 45.1C
  and 400. torr at 104.0C. What is its heat of
  vaporization?
• A)39.0 kJ/mol
• B)46.0 kJ/mol
• C)590 kJ/mol
• D)710 kJ/mol
• E)none of the above

19
Problems

• Liquid sodium can be used as a heat transfer
  fluid. Its vapor pressure is 40.0 torr at 633C
  and 400.0 torr at 823C. Calculate its heat of
  vaporization.
• A)43.4 kJ/mol
• B)52.5 kJ/mol
• C)70.6 kJ/mol
• D)1.00 x 102 kJ/mol
• E)none of the above

20
Phase Changes Solids, Liquids, and Gases

• Vaporization and Condensation
• Vaporization liquid changes to gas
• Surface molecules have higher kinetic energy than
  potential energy
• Endothermic
• Condensation gas changes into a liquid
• Gas molecules lose some of their kinetic energy
• Collision
• exothermic

21
Phase Changes Solids, Liquids, and Gases

• ?Hvap - ?Hcond

22
Phase Changes Solids, Liquids, and Gases

• Melting and Freezing
• Melting solid changes to liquid
• A temperature was reached so that the molecules
  have sufficient energy to break the
  intermolecular forces of a solid
• Endothermic process
• Heat required is the heat of fusion
• Freezing (solidification, crystallization)
  liquid changes to solid
• Exothermic process
• ?Hfus -?Hcrys

23
Cooling Curve
24
Problems

• Liquid ammonia (boiling point -33.4C) can be
  used as a refrigerant and heat transfer fluid.
  How much energy is needed to heat 25.0 g of
  NH3(l) from -65.0C to -12.0C?
• Specific heat capacity, NH3(l) 4.7 J/(gK)
• Specific heat capacity, NH3(g) 2.2 J/(gK)
• Heat of vaporization 23.5 kJ/mol M
• Molar mass, M 17.0 g/mol
• A)5.5 kJ
• B)6.3 kJ
• C)39 kJ
• D)340 kJ
• E)590 kJ

25
Phase Changes Solids, Liquids, and Gases

• Sublimation and Deposition
• Sublimation solid changes directly to a gas
• Exothermic process
• Deposition gas directly converted to solid
• Endothermic process
• ?Hsub - ?Hdep

26
Phase Changes Solids, Liquids, and Gases

• Phase Diagram

27
Problems

• Examine the following phase diagram and identify
  the feature represented by point B.
• A)melting point
• B)triple point
• C)critical point
• D)sublimation point
• E)boiling point

28
Problems

• Examine the phase diagram for the substance
  Bogusium (Bo) and select the correct statement.
• A)Bo(s) has a lower density than Bo(l).
• B)The triple point for Bo is at a higher
  temperature than the melting point for Bo.
• C)Bo changes from a solid to a liquid as one
  follows the line from C to D.
• D)Bo changes from a liquid to a gas as one
  follows the line from C to D.
• E)Point B represents the critical temperature and
  pressure for Bo.

29
Water An Important Liquid with Unusual Properties

• The H-bonding abilitiy of the water molecule

30
Water An Important Liquid with Unusual Properties
31
Types of Solids

• Ionic
• Structural Unit
• Positive and negative ions
• No discrete units
• Intermolecular Force
• Attraction among charges lattice energy
• Properties
• Hard
• Brittle
• High melting Points
• Poor conductors as solids but good as liquids
• Often water soluble

32
Types of Solids

• Metallic
• Structural Units
• Metal atoms positive metal ions surrounded by
  electrons sea
• Forces
• Metallic Bonding electrostatic attraction among
  metal ions and electrons
• Properties
• Malleable
• Ductile
• Good electrical conductors in solid or liquid
• Good heat conductors
• Wide range of hardness and melting points

33
Types of Solids

• Molecular Solid
• Structural Unit
• Molecules with covalent bonds
• Forces
• London Forces
• Dipole dipole forces
• Hydrogen bonding
• Properties
• Low to moderate melting points and boiling points
• Soft
• Poor electrical conductors as solids or liquids

34
Types of Solids

• Network Solids
• Structural Unit
• Atoms are held in an infinite one-, two- or three
  dimensional network
• Forces
• Covalent Bonds
• Directional electron-pair bonds
• Properties
• Wide range of hardness and melting points
• Mostly poor electrical conductors

35
Types of Solids

• Amorphous
• Structural Units
• Covalently bonded networks or atoms or collection
  of large molecules with no long range regularity
  in their arrangement
• Forces
• Covalent bonds
• Directional electron-pair bonds
• Properties
• Noncrystalline
• Wide temperature range for melting
• Poor electrical conductors with some exceptions
• Examples
• Polymers, glass

36
Crystalline Solids

• The regularity of the atoms within a crystal can
  help explain
• A solids properties
• Chemical formula
• The shape of a crystalline solid reflects the
  shape of the crystal lattice
• Crystal lattice the orderly repeating
  arrangement of ions, molecules, or atoms that
  shows the position of each individual particle

37
Crystalline Solids

• Unit cell - smallest segment of a crystal lattice

38
Crystalline Solids

• 3-D Crystalline Lattices can be divided into 7
  types of unit cells
• Cubic Unit Cell
• Simple cubic (sc)
• Body-centered cubic (bcc)
• Face-centered cubic (fcc)
• Unit Cells and Density
• Dependent on packing

39
Problems

• A metal such as chromium in the body-centered
  cubic lattice will have _______________ atom(s)
  per unit cell.
• A)1
• B)2
• C)3
• D)4
• E)9

40
Problems

• A metal such as chromium in the body-centered
  cubic lattice will have _______________ atom(s)
  per unit cell.
• A)1
• B)2
• C)3
• D)4
• E)9

41
Network Solids

• Network Solids huge molecule in which all atoms
  are connected to all others via a network
• Planar network solid
• Dimensional network

42

• Which one of the following substances does not
  exist in the indicated solid type?
• A)graphite - network
• B)Na - metallic
• C)SiO2 - molecular
• D)NaCl - ionic
• E)diamond - network

43
Material Science

• Science of the relationships between the
  structure and the chemical and physical
  properties of materials
• Properties
• Strength
• Density
• Ease of formation
• Reaction to acid, stress, magnetic field, high
  pressure, and heat
• Electrical conductivity
• Structure
• Crystallinity

44
Material Science
45
Material Science
46
Material Science

• n? 2dsin?
• n 1 most of the time
• ? wavelength of the x-ray
• ? angle of scattering
• d distance between atomic layers

47
Metals, Semiconductors, and Insulators

• Metals
• High electrical conductivity
• High thermal conductivity
• Ductile and malleable
• Insoluble in water and other common solvents

48
The band of molecular orbitals in lithium metal
49
Electrical conductivity in a conductor,
semiconductor, and insulator
conductor
insulator
semiconductor
50
Problems

• A temperature increase causes __________________
  in the conductivity of a semiconductor.
• A)a decrease
• B)an increase
• C)a modulation
• D)an increase or decrease (depending on the
  semiconductor)
• E)no change

51
Problems

• The energy gap between the conduction band and
  the valence band is large for
• A)conductors
• B)semiconductors
• C)superconductors
• D)insulators
• E)alloys

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Homework

• 18, 20, 22, 24, 29, 30, 31, 34, 38, 42, 48, 50, 75