A combination of two or more
substances that are not chemically
combined and can be separated
by physical means.
A solution is a homogeneous mixture of two
or more substances in a single phase.
Thoroughly mixed
Same Composition
Throughout
Same Properties
Throughout
What makes up a solution?
• Solute: the substance being dissolved
• Solvent: the substance doing the
dissolving
Name the solute and solvent:
solution
solute(s)
solvent
Ocean water
salt
water
Coca-cola
Sugar, carbon dioxide
water
Humid air
Water vapor
air
Examples of
solutions
Gas
S
o
l
u
t
e
Solvent
Gas
Oxygen and
other gases in
nitrogen (air)
Liquid
Solid
Carbon dioxide
in water
(carbonated
water)
Hydrogen dissolves
rather well in
metals; platinum
has been studied as
a storage medium
Water in
activated
charcoal;
moisture in
wood
Steel, brass,
other metal
alloys
Liquid
Water vapor in
air (humidity)
Ethanol (common
alcohol) in water;
various
hydrocarbons in
each other
(petroleum)
Solid
The odor of a solid
results from
molecules of that
solid being
dissolved in the air
Sucrose (table
sugar) in water;
sodium chloride
(table salt) in
water
Adapted from http://en.wikipedia.org/wiki/Solution
What types of solutions are
there?
•Aqueous solutions (aq): solutions in
which water is the solvent.
•Electrolytes: specific aqueous solutions in
which the solute dissolves to form ions.
•Tinctures: solutions in which alcohol is
the solvent.
•Alloys: solid solution of two or more metals.
•Amalgams: specific alloys in which one of the
metals is mercury.
If the particles in a
solvent are so large that
they settle out unless
the mixture is constantly
stirred or agitated, the
mixture is called a
suspension.
Muddy Water
Particles that are intermediate in
size between those in solutions
and suspensions form mixtures
known as colloidal dispersions,
or colloids.
paints, mud, gelatin, milk,
mayonnaise, shaving cream,
smoke, fog, butter
•A beam of light
distinguishes a colloid
from a solution.
•The particles in a
colloid will scatter light,
making the beam
visible.
NaCl
Solution
Gelatin and
Water
Dissolves in water to give
a solution that conducts
an electric current.
Ionic Compounds (NaCl)
Highly Polar Molecular
Compounds (HCl)
Dissolves in water to give
a solution that does not
conduct electrical current.
Neutral solute molecules (not
charged particles).
Sugar is a nonelectrolyte.
What does soluble
mean?
Is sugar more
soluble in hot
tea or iced
tea?
By experience you know
that sugar will dissolve in
tea.
Sugar is described as
being “soluble” in tea.
Soluble – capable of
dissolving in a particular
solvent.
Back to tea. Why does sugar dissolve faster in hot
tea versus iced tea?
Temperature
•Heating a solvent
allows solvent
molecules to move
faster and their kinetic
energy increases.
•At higher temperatures, collisions between
solvent molecules and the solute are more
frequent and are of higher energy.
•Helps to separate solute particles from each other and
have better dispersion among the solvent molecules.
•Dissolution can be sped
up if surface area of solute is
increased.
•Crushing sugar cubes
increases its surface area.
•The more finely divided a substance is, the greater
the surface area and more quickly it dissolves.
•Stirring or shaking helps to
disperse the solute particles
and bring fresh solvent into
contact with the solute surface.
•Contact between the solute
and solvent is increased.
Is there a limit to the amount of salt that will dissolve
in a glass of water?
Suppose you spoon copper sulfate into
water until no more will dissolve.
There is a little copper sulfate in the bottom.
This means that copper sulfate is dissolving
into the water as fast as copper sulfate is
crystallizing out onto the bottom.
That is dynamic equilibrium.
Solution equilibrium is the physical
state in which the opposing
processes of dissolution and
crystallization of a solute occur at
equal rates.
A solution that contains the maximum amount of
dissolved solute is described as a saturated solution.
A solution that contains less solute than a saturated
solution under the existing conditions is an
unsaturated solution.
A supersaturated solution is a solution that
contains more dissolved solute than a saturated
solution contains under the same conditions.
How does a supersaturated solution form?
Heat
saturated
solution
Let cool
slowly –
unstable
If disturbed –
will rapidly
crystallize
The solubility of a substance is the
amount of that substance required
to form a saturated solution with a
specific amount of solvent at a
specified temperature.
Why does vinegar dissolve in water but
not in vegetable oil?
Type of bonding, polarity or nonpolarity of molecules,
and the intermolecular forces between the solute and
the solvent.
Ionic Compounds
Nonpolar Compounds
Polar Solvents
Nonpolar Solvents
Double, Double, Toil and
Trouble…
• What can happen when we mix
two liquids together?
Either they mix, or they don’t!
• If two liquids mix well together, and one
dissolves in the other, we call them miscible
(think “mixable”)
• If two liquids do not mix well together, and
they separate, we call them immiscible
(think “unmixable”)
Like Oil & Water…
• How do we know that two liquids will be
miscible or immiscible?
• Rule of thumb: “Like dissolves Like”
– Polar solutes will dissolve in polar solvents.
– Nonpolar solutes will dissolve in nonpolar
solvents.
• Water is the “universal solvent”.
…And never the two shall
meet?
• How can we mix polar and nonpolar
molecules into solutions? Can it be
done?
• We use emulsifiers – agents that have
both polar and nonpolar ends to join the
two unlike molecules together.
– Creates an emulsion: A suspension of
small globules of one liquid in a second
liquid with which the first will not mix.
The concentration of a solution is a measure
of the amount of solute in a given amount of
solvent or solution.
Concentration Units
Molarity is the number of
moles of solute in one
liter of solution.
The symbol for molarity is M.
For example, a “one molar” solution of sodium hydroxide, NaOH,
contains one mole of NaOH in every liter of solution.
The concentration of this solution would be written as 1 M NaOH.
amount of solute (mol)
molarity (M) 
volume of solution (L)
Note that a 1 M solution is not made by adding
1 mol of solute to 1 L of solvent.
Molality is the concentration
of a solution expressed in
moles of solute per kilogram
of solvent.
The symbol for molality is m.
For example, a “one molal” solution of sodium hydroxide, NaOH,
contains one mole of NaOH dissolved in exactly 1 kg of solvent.
The concentration of this solution would be written 1 m NaOH.
moles solute
molality 
mass of solvent (kg)