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Unit 6 – Solids, Liquids
and Solutions
Intermolecular Forces
Forces of attraction between
different molecules rather than
bonding forces within the same
molecule.
Dipole-dipole attraction
Hydrogen bonds
Dispersion forces
Forces and Phases
o Substances with very little intermolecular
attraction exist as gases
o Substances with strong intermolecular
attraction exist as liquids
o Substances with very strong
intermolecular (or ionic) attraction exist
as solids
Phase
Differences
Solid – definite volume and shape; particles packed
in fixed positions; particles are not free to move
Liquid – definite volume but indefinite shape;
particles close together but not in fixed positions;
particles are free to move
Gas – neither definite volume nor definite shape;
particles are at great distances from one another;
particles are free to move
Three Phases of Matter
Effect of Pressure on Boiling Point
Boiling Point of Water at Various Locations
Location
Feet above
sea level
Patm (kPa)
Boiling
Point (C)
Top of Mt. Everest, Tibet
29,028
32
70
Top of Mt. Denali, Alaska
20,320
45.3
79
Top of Mt. Whitney, California
14,494
57.3
85
Leadville, Colorado
10,150
68
89
Top of Mt. Washington, N.H.
6,293
78.6
93
Boulder, Colorado
5,430
81.3
94
900
97.3
99
10
101.3
100
-282
102.6
100.3
Madison, Wisconsin
New York City, New York
Death Valley, California
Types of Solids
Crystalline Solids: highly regular arrangement
of their components [table salt (NaCl), pyrite
(FeS2)].
Representation of Components in
a Crystalline Solid
Lattice: A 3-dimensional
system of points
designating the centers
of components (atoms,
ions, or molecules) that
make up the substance.
Unit Cell
The smallest portion of a crystal lattice that
shows the three-dimensional pattern of the
entire lattice
Packing in Metals
Model: Packing uniform, hard spheres
to best use available space. This is
called closest packing. Each atom has
12 nearest neighbors.
Types of Solids
Amorphous solids:
considerable
disorder in their
structures (glass
and plastic).
constant
Temperature remains __________
during a phase change.
Water phase changes
Phase Diagram
Represents phases as a function of
temperature and pressure.
Critical temperature: temperature above
which the vapor can not be liquefied.
Critical pressure: pressure required to
liquefy AT the critical temperature.
Critical point: critical temperature and
pressure (for water, Tc = 374°C and 218
atm).
Phase changes by Name
Water
Water
Carbon dioxide
Carbon
dioxide
Carbon
Carbon
Sulfur
Solutions Classification
are
homogeneous
mixtures
of Matter
Solute
A solute is the dissolved substance in a
solution.
Salt in salt water
Sugar in soda drinks
Carbon dioxide in soda drinks
Solvent
A solvent is the dissolving medium in a
solution.
Water in salt water
Water in soda
Solvents
Solvents at the hardware store
Dissolution of sodium Chloride
Concentrated vs. Dilute
Heat of Solution
The Heat of Solution is the amount of heat
energy absorbed (endothermic) or released
(exothermic) when a specific amount of
solute dissolves in a solvent.
Substance Heat of Solution
(kJ/mol)
NaOH
-44.51
NH4NO3
+25.69
KNO3
+34.89
HCl
-74.84
Electrolytes vs. Nonelectrolytes
The ammeter measures the flow of electrons (current)
through the circuit.
If the ammeter measures a current, and the bulb
glows, then the solution conducts.
If the ammeter fails to measure a current, and the
bulb does not glow, the solution is non-conducting.
Definition of Electrolytes and
Nonelectrolytes
An electrolyte is:
A substance whose aqueous solution conducts
an electric current.
A nonelectrolyte is:
A substance whose aqueous solution does not
conduct an electric current.
Try to classify the following substances as
electrolytes or nonelectrolytes…
Electrolytes?
1.Pure water
2.Tap water
3.Sugar solution
4.Sodium chloride solution
5.Hydrochloric acid solution
6.Lactic acid solution
7.Ethyl alcohol solution
8.Pure sodium chloride
ELECTROLYTES:
NONELECTROLYTES:
Tap water (weak)
Pure water
NaCl solution
Sugar solution
HCl solution
Ethanol solution
Lactate solution (weak)
Pure NaCl
But why do some compounds conduct electricity in
solution while others do not…?
Answers to Electrolytes
Suspensions and Colloids
Suspensions and colloids are NOT solutions.
Suspensions: The particles are so large that
they settle out of the solvent if not
constantly stirred.
Colloids: The particle is intermediate in size
between those of a suspension and those of a
solution.
Types of Colloids
Examples
Dispersing
Medium
Dispersed
Substance
Colloid Type
Fog, aerosol sprays
Gas
Liquid
Aerosol
Smoke, airborne bacteria
Gas
Solid
Aerosol
Whipped cream, soap suds
Liquid
Gas
Foam
Milk, mayonnaise
Liquid
Liquid
Emulsion
Paint, clays, gelatin
Liquid
Solid
Sol
Marshmallow, Styrofoam
Solid
Gas
Solid foam
Butter, cheese
Solid
Liquid
Solid emulsion
Ruby glass
Solid
Solid
Solid sol
The Tyndall Effect
Colloids scatter
light, making a
beam visible.
Solutions do not
scatter light.
Which glass
contains a colloid?
colloid
solution
Factors Effecting Solubility
 The solubility of MOST solids increases
with temperature.
 The rate at which solids dissolve
increases with increasing surface area of
the solid.
 The solubility of gases decreases with
increases in temperature.
 The solubility of gases increases with
the pressure above the solution.
Therefore…
Solids tend to dissolve best when:
o Heated
o Stirred
o Ground into small particles
Liquids tend to dissolve best when:
o The solution is cold
o Pressure is high
Saturation of Solutions
 A solution that contains the maximum amount of
solute that may be dissolved under existing
conditions is saturated.
 A solution that contains less solute than a
saturated solution under existing conditions is
unsaturated.
 A solution that contains more dissolved solute
than a saturated solution under the same
conditions is supersaturated.
Solubility Chart
Calculations of Solution Concentration
Concentration - A measure of the amount of
solute in a given amount of solvent or solution
Grams per liter - the mass of solute divided
by the volume of solution, in liters
Molarity - moles of solute divided by the volume
of solution in liters
Parts per million – the ratio of parts (mass) of
solute to one million parts (mass) of solution
Percent composition - the ratio of one part of
solute to one hundred parts of solution, expressed
as a percent
Colligative Properties
Colligative properties are those that depend
on the concentration of particles in a
solution, not upon the identity of those
properties.
 Boiling Point Elevation
 Freezing Point Depression
 Osmotic Pressure
Freezing Point Depression
Each mole of solute particles lowers the
freezing point of 1 kilogram of water by
1.86 degrees Celsius.
Kf = 1.86 C  kilogram/mol
Boiling Point Elevation
Each mole of nonvolatile solute particles
raises the boiling point of 1 kilogram of
water by 0.51 degrees Celsius.
Kb = 0.51 C  kilogram/mol
Freezing Point Depression and Boiling
Point Elevation Constants
Properties of Acids
 Acids taste sour
 Acids effect indicators
 Blue litmus turns red
 Methyl orange turns red
 Acids have a pH lower than 7
 Acids are proton (hydrogen ion, H+) donors
 Acids react with active metals, produce H2
 Acids react with carbonates
 Acids neutralize bases
Acids you SHOULD know:
Strong Acids
Weak Acids
Sulfuric acid, H2SO4
Phosphoric acid, H3PO4
Hydrochloric acid, HCl
Acetic acid, HC2H3O2
Nitric acid, HNO3
Sulfuric Acid
 Highest volume production of any chemical in
the U.S.
 Used in the production of paper
 Used in production of fertilizers
 Used in petroleum refining
Thick clouds of sulfuric acid are a
feature of the atmosphere of Venus.
(image provided by NASA)
Nitric Acid
• Used in the production of
fertilizers
• Used in the production of
explosives
• Nitric acid is a volatile acid
– its reactive components
evaporate easily
• Stains proteins (including
skin!)
Hydrochloric Acid
• Used in the pickling of
steel
• Used to purify magnesium
from sea water
• Part of gastric juice, it
aids in the digestion of
protein
• Sold commercially as
“Muriatic acid”
Phosphoric Acid
o A flavoring agent in sodas
o Used in the manufacture
of detergents
o Used in the manufacture
of fertilizers
o Not a common laboratory
reagent
Acetic Acid
Used in the manufacture of
plastics
Used in making
pharmaceuticals
Acetic acid is the acid
present in vinegar
Acids are Proton Donors
Monoprotic acids
Diprotic acids
HCl
H2SO4
HC2H3O2
H2CO3
HNO3
Triprotic acids
H3PO4
Strong Acids vs. Weak Acids
Strong acids are assumed to be 100%
ionized in solution (good proton donors).
HCl
H2SO4
HNO3
Weak acids are usually less than 5%
ionized in solution (poor proton donors).
H3PO4
HC2H3O2
Organic acids
Strong Acid Dissociation
Weak Acid Dissociation
Organic Acids
Organic acids all contain the “carboxyl” group,
sometimes several of them.
The carboxyl group is a poor proton donor,
so ALL organic acids are weak acids.
Examples of Organic Acids
Citric acid in citrus fruit
Malic acid in sour apples
Deoxyribonucleic acid, DNA
Amino acids, the building blocks of
protein
 Lactic acid in sour milk and sore muscles
 Butyric acid in rancid butter




Acids Effect Indicators
Blue litmus paper turns red in contact
with an acid.
Acids Have
a pH less
than 7
Acids React with Active Metals
Acids react with active metals to form
salts and hydrogen gas.
Mg + 2HCl  MgCl2 + H2(g)
Zn + 2HCl  ZnCl2 + H2(g)
Mg + H2SO4  MgSO4 + H2(g)
Acids React with Carbonates
2HC2H3O2 + Na2CO3
2 NaC2H3O2 + H2O + CO2
Effects of Acid Rain on Marble
(calcium carbonate)
George Washington:
BEFORE
George Washington:
AFTER
Acids Neutralize Bases
Neutralization reactions ALWAYS produce a
salt and water.
HCl + NaOH  NaCl + H2O
H2SO4 + 2NaOH  Na2SO4 + 2H2O
2HNO3 + Mg(OH)2  Mg(NO3)2 + 2H2O
Properties of Bases
 Bases taste bitter
 Bases effect indicators
 Red litmus turns blue
 Phenolphthalein turns purple
 Bases have a pH greater than 7
 Bases are proton (hydrogen ion, H+) acceptors
 Solutions of bases feel slippery
 Bases neutralize acids
Examples of Bases




Sodium hydroxide (lye), NaOH
Potassium hydroxide, KOH
Magnesium hydroxide, Mg(OH)2
Calcium hydroxide (lime), Ca(OH)2
Bases Effect Indicators
Red litmus paper turns blue
in contact with a base.
Phenolphthalein
turns purple in a
base.
Bases have
a pH
greater
than 7
Bases Neutralize Acids
Milk of Magnesia contains
magnesium hydroxide, Mg(OH)2,
which neutralizes stomach acid,
HCl.
2 HCl + Mg(OH)2
MgCl2 + 2 H2O