Intermolecular forces, Liquids, and Solids

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Chapter 11

• Intermolecular forces, Liquids, and Solids

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Intermolecular Forces

• Forces between molecules

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Intermolecular forces are important because they
determine if a substance is a solid, liquid, or
gas

• Intermolecular Force

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Important!!!

• Intermolecular forces are much weaker than ionic,
  metallic, or covalent bonds!!!

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4 Types

• Ion-Dipole

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4 Types

• 2. Dispersion Forces

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4 Types

• 2. Dispersion Forces
• Between nonpolar molecules
• Melting point I2 ? 113oC

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4 Types

• 2. Dispersion Forces
• Between nonpolar molecules
• Melting point I2 ? 113oC
• Br2 ? -8 oC

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4 Types

• 2. Dispersion Forces
• Between nonpolar molecules
• Melting point I2 ? 113oC
• Br2 ? -8 oC
• Cl2 ? -101oC

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4 Types

• 2. Dispersion Forces
• Between nonpolar molecules
• Melting point I2 ? 113oC
• Br2 ? -8 oC
• Cl2 ? -101oC

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4 Types

• 2. Dispersion Forces
• Between nonpolar molecules
• boiling point pentane ? 36oC

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4 Types

• 2. Dispersion Forces
• Between nonpolar molecules
• boiling point pentane ? 36oC
• neopentane?10 oC

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4 Types

• 2. Dispersion Forces
• Between nonpolar molecules
• boiling point pentane ? 36oC
• neopentane?10 oC

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4 Types

• 3. Dipole-Dipole Force

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4 Types

• 3. Dipole-Dipole Force

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4 Types

• 4. Hydrogen Bond

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Consequences of hydrogen bonding in water

• 1. Solid is less dense than liquid
• Ice floats on water!

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Water ? Ice

Hydrogen bonds

More Dense
Less Dense
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Consequences of hydrogen bonding in water

• 2. Water expands when it freezes

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Water ? Ice

Hydrogen bonds

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Consequences of hydrogen bonding in water

• 3. Water has a very high boiling point compared
  to similar substances.

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Consequences of hydrogen bonding in water

• 3. Water has a very high boiling point compared
  to similar substances.
• H2Se ? -45o C

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Consequences of hydrogen bonding in water

• 3. Water has a very high boiling point compared
  to similar substances.
• H2Se ? -45o C
• H2S ?-61o C

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Consequences of hydrogen bonding in water

• 3. Water has a very high boiling point compared
  to similar substances.
• H2Se? -45o C H2S ?-61o C
• H2O ?

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Consequences of hydrogen bonding in water

• 3. Water has a very high boiling point compared
  to similar substances.
• H2Se? -45o C
• H2S ?-61o C
• H2O ? 100o C

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Liquids

• Properties

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Liquids

• Properties
•        

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Heating Curves and Phase Changes

• Shows how the temperature of an object changes as
  it is heated and transforms from a solid to a
  liquid to a gas

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Heating curve of water
HeatHeat
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What happens during a phase change?

• In the case of melting ice, the energy is used to
  actually melt the ice (break the hydrogen bonds).
  Only once all the ice has melted can the
  temperature begin to rise again.

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Energy used to break these hydrogen bonds
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The energy needed to melt one mole of ice at 0o
C is called the heat of fusion or ?Hfus  
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The energy needed to boil one mole of water at10
0o C is called the heat of vaporization or
?Hvap  
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Vapor Pressure

• Evaporation Conversion of a liquid to vapor
  .-a vapor is the gaseous state of a substance
  that is normally a liquid at room
  temperature-    

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Vapor Pressure

• Evaporation Conversion of a liquid to vapor .
• Occurs On the surface
• At any temperature but does require energy
•    
•    
•    

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When there is no change in the level of the
liquid the system is at equilibrium.   
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When there is no change in the level of the
liquid the system is at equilibrium.  The
pressure exerted by the vapor on the walls of the
container at this point is called vapor
pressure.       

•    

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When there is no change in the level of the
liquid the system is at equilibrium.  The
pressure exerted by the vapor on the walls of the
container at this point is called vapor
pressure.     As temperature increases, vapor
pressure increases  
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Boiling

• Conversion of a liquid to a gas
• Occurs  In the body of the liquid At a
  specific temperature
•    
•    
•          

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 Boiling point is the temperature at which the
force exerted by the air (air pressure) equals
the pressure exerted by the vapor (vapor
pressure).  
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Phase Diagrams

• Phase diagrams show the relationship between the
  temperature, pressure and phase of matter

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Phase diagram for water
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Phase diagram for carbon
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Solids

• Amorphous
• Crystalline

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Molecular Solids

• Made of molecules
• Held together by weak IMF
• Soft
• Low MP
• Many are gases and liquids

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Covalent Network Solids

• Giant molecule held together by covalent bonds
• Very hard
• Very high MP

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Ionic Solids

• Made of ions
• Held together by electrostatic attractions
• Hard and brittle
• Intermediate MP

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Metallic Solids

• Made of metal atoms
• Bonding is due to a sea of electrons
• Soft to hard
• Various MP
• Conduct heat and electricity

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Chapter 13

• Solutions

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Solutions

• A homogeneous mixture
• Solvent - does the dissolving
• Solute - substance being dissolved

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Types of Solutions

• Solid dissolved in a liquid

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Types of Solutions

• Solid dissolved in a liquid
• Salt and water
• Sugar and water

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Types of Solutions

• Gas dissolved in a liquid

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Types of Solutions

• Gas dissolved in a liquid
• Soda (carbon dioxide in water)
• Glass cleaner (ammonia in water)

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Types of Solutions

• Liquid dissolved in a liquid

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Types of Solutions

• Liquid dissolved in a liquid
• Whiskey, beer , wine (alcohol dissolved in water)

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Types of Solutions

• Gas dissolved in a Gas

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Types of Solutions

• Gas dissolved in a Gas
• Air (oxygen dissolved in nitrogen)

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Types of Solutions

• Solid dissolved in a Solid

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Types of Solutions

• Solid dissolved in a Solid
• Steel (carbon dissolved in iron)

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Types of Solutions

• Solid dissolved in a Solid
• Steel (carbon dissolved in iron)
• Stainless Steel (carbon and chromium dissolved in
  iron)

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The Solution Process

• What happens when salt dissolves in water

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Energy Changes in Solution

• Simply put, three processes affect the energetics
  of solution
• separation of solute particles,
• separation of solvent particles,
• new interactions between solute and solvent.

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Energy Changes in Solution

• The enthalpy change of the overall process
  depends on ?H for each of these steps.

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Why Do Endothermic Processes Occur?

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The rate of solution is affected by
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Solubility

• How much solute can be dissolved in a solvent

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Saturated

• The maximum amount of solute that the solvent can
  hold is dissolved

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Unsaturated

• Less than maximum amount of solute that the
  solvent can hold is dissolved

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The amount of solute that is dissolved is called
concentration
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The amount of solute that is dissolved is called
concentration

• Molarity(M) moles solute/liter of solution

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The amount of solute that is dissolved is called
concentration

• Mass mass solute/mass solution x 100

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The amount of solute that is dissolved is called
concentration

• ppm mass of solute/mass of solution x 106

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The amount of solute that is dissolved is called
concentration

• Mole fraction(X) moles solute/total number of
  moles

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The amount of solute that is dissolved is called
concentration

• Molality(m) moles of solute/kilograms of
  solvent

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Supersaturated

• More than maximum amount of solute that the
  solvent can hold is dissolved unstable!

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Factors that influence solubility
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Factors that influence solubility

• 1. Nature of solute and solvent

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Factors that influence solubility

• 2. Pressure

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Factors that influence solubility

• 3. Temperature

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Properties of Solutions

• When a solute is dissolved in a solvent there are
  changes in certain physical properties of the
  solvent. We call these properties colligative
  properties

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Vapor Pressure Lowering
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Vapor Pressure Lowering

• The addition
• of a solute to a
• solvent will cause
• a decrease in the
• vapor pressure of
• the solution Pure Water Salt Water
• Higher vapor
  pressure Lower vapor pressure
• 
  Evaporates faster Evaporates slower

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Raoults Law

• PA XAPoA
• Where XA mole fraction of solvent and PoA
  vapor pressure of the pure solvent

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PA XAPoAWhere XA mole fraction of solvent
and PoA vapor pressure of the pure solvent

• At 25o C the vapor pressure of pure water is 24
  mm Hg. Calculate the vapor pressure of a
  solution made by adding 5 moles of alcohol to 75
  moles of water

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Boiling Point Elevation
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Boiling Point Elevation

• The addition of a solute to a solvent will cause
  the solvent to boil at a higher temperature than
  the pure solvent.

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• Calculate the boiling point 2.0 kg of water that
  has 0.50 moles of ethanol dissolved in it.

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• Calculate the boiling point 2.0 kg of water that
  has 0.50 moles of ethanol dissolved in it.
• ?Tb kbm

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• Calculate the boiling point 2.0 kg of water that
  has 0.50 moles of NaCl dissolved in it.
• ?Tb kbm

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Freezing Point Depression
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Freezing Point Depression

• The addition of a solute to a solvent will cause
  the solvent to freeze at a lower temperature than
  the pure solvent

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calcium chloride
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Calculate the freezing point 2.0 kg of water that
has (a) 0.5 moles of alcohol dissolved in
it.(b)sodium chloride. (c)calcium chloride.?Tf
kf m
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Osmosis

• The passage of solvent molecules through a
  semipermeable membrane from a dilute solution to
  a more concentrated one

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Salt water
Cell wall
Water (small amount salt)
Na1
H2O
.
Cl-1
H2O
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Hypertonic Solution
Salt water
Water
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Cell shrinks
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Applications

• Food preservation
• Making pickles
• Dehydration from drinking alcohol

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Pure water
Cell wall
Na1
Water (small amount salt
Cl-1
H2O
.
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Hypotonic Solution
Salt water
Water
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Cell swells
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Isotonic Solution
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Reverse Osmosis

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Reverse Osmosis
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Reverse Osmosis

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Reverse Osmosis

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Colloids
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Colloids

• Solutions particles are invisible and do not
  settle out.

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Colloids

• Solutions - particles are invisible and do not
  settle out.
• Suspension particles are visible and some do
  settle out.

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Colloids

• Solutions - particles are invisible and do not
  settle out.
• Suspensions - particles are visible and some do
  settle out.
• Colloids particle are visible with
  magnification but do not settle out, they are
  trapped.

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Intermolecular Forces, Liquids, Solids, and
Solutions

• Explain the different types of IMF

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Intermolecular Forces, Liquids, Solids, and
Solutions

• Consequences of Hydrogen Bonding

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Intermolecular Forces, Liquids, Solids, and
Solutions

• Relate IMF to physical properties

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Intermolecular Forces, Liquids, Solids, and
Solutions

• Identify the attractive forces in solids

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Intermolecular Forces, Liquids, Solids, and
Solutions

• Explain the difference between colloids,
  suspensions, and solutions and give examples

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Intermolecular Forces, Liquids, Solids, and
Solutions

• Calculate , ppm, X, M, m

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Intermolecular Forces, Liquids, Solids, and
Solutions

• Explain the factors that influence solubility

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Intermolecular Forces, Liquids, Solids, and
Solutions

• Calculate PA, ? TB, ?TF, ?, and molecular weight

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