Solutions
SPS6. Students will investigate the properties of
solutions.
a. Describe solutions in terms of:
-solute/solvent
-conductivity
-concentration
b. Observe factors affecting the rate a solute
dissolves in a specific solvent.
c. Demonstrate that solubility is related to
temperature by constructing a solubility curve.
Solutions

Solution (homogeneous mixture): a mixture
that has the same composition, color,
density, and taste throughout

Solute - substance
being dissolved

Solvent – substance
doing the dissolving
and is present in a
greater amount
Nonliquid Solutions

Solutions can also be gaseous or even
solid.

Air is a solution of 78 percent nitrogen, 20
percent oxygen, and small amounts of
other gases such as argon, carbon dioxide,
and hydrogen.
Nonliquid Solutions


Solid solutions are
known as alloys.
They are made by
melting the metal
solute and solvent
together.
Sterling silver contains
92.5 percent silver
and 7.5 percent
copper.
Rate of Dissolving

Solids dissolve faster...
1.
More stirring
2.
Small particle size
(increased surface area)
3.
High temperature
4.
Controlling the process (all
3 at the same time)
Rate of Dissolving

Gases dissolve faster...
1.
No shaking or stirring
2.
High pressure
3.
Low temperature
Solubility
• If you continue adding
sugar to lemonade,
NaCl dissolving in water
eventually the point is
reached when no more
sugar dissolves, and the
excess granules sink to the
bottom of the glass.
Animation
Animation
Solubility

Solubility
Maximum grams of solute that will dissolve in
100 g of solvent at a given temperature
 Varies with temperature
 Based on a saturated solution

Solubility

In the beaker to the right, 1 g of
solute A dissolves completely,
but additional solute does not
dissolve and falls to the bottom
of the beaker.

However, 1 g of solute B
dissolves completely and two
more grams also dissolve
before solute begins to fall to
the bottom of the beaker.

If the temperature of the
solvent is the same in both
beakers, you can conclude that
substance B is more soluble
than substance A.
Solubility Curve
• Each line on the graph is
called a solubility curve for a
particular substance.
•You can use a solubility curve
to figure out how much solute
will dissolve at any temperature
given on the graph.
•Line = Saturated Solution
•Above the Line = Supersaturated Solution
•Below the Line = Unsaturated
Solution
Solubility Curve

Solubility Curve
 shows the dependence of
solubility on temperature
Solubility Curves of Pure Substances
150
140
130
KI
120

Solutes whose curves move
upward with an increase in
temperature are typically
solids because the solubility
of solids increases with
increased temperature.
Solutes whose curves move
downward with an increase
in temperature are typically
gases because the solubility
of gases decreases with
increased temperature.
110
NaNO3
100
grams solute per 100 grams H2O

90
KNO3
80
70
60
NH4Cl
NH3
50
KCl
40
NaCl
30
20
KClO3
10
Ce2(SO4)3
0
0
10
20
30
40
50
60
Tem perature/Celsuis
70
80
90
100
Solubility Curve
Solubility Curves of Pure Substances
Solubility Curve
 Which substance is the
most soluble at 0°C?
150
140
130
KI
120
110


What is the most NH3
that can be dissolved in
100 g of water at 65°C?
How much NH4Cl will
dissolve in 100 g of
water at 90°C?
NaNO3
100
grams solute per 100 grams H2O

90
KNO3
80
70
60
NH4Cl
NH3
50
KCl
40
NaCl
30
20
KClO3
10
Ce2(SO4)3
0
0
10
20
30
40
50
60
Tem perature/Celsuis
70
80
90
100
Solubility Curve
Concentration

Concentrated solution


Large amount of solute is dissolved in the
solvent
Dilute solution

Small amount of solute is dissolved in the
solvent
Concentration

Percent (%) by Volume
Usually liquid in liquid
 EX: 10% juice = 10mL juice + 90mL water


Percent (%) by Mass
Usually solid in liquid
 EX: 20% NaCl = 20g NaCl + 80g water

Concentration: Saturated

A saturated solution is a solution
that contains all the solute it can
hold at a given temperature.

Generally, as the temperature of a
liquid solvent increases, the amount
of solid solute that can dissolve in it
also increases. This table shows
the amounts of a few solutes that
can dissolve in 100 g of water at
different temperatures, forming
saturated solutions.

On a solubility chart, the curve
shows the number of grams of
solute in a saturated solution
containing 100 mL or 100 g of water
at a certain temperature.
Concentration: Unsaturated

An unsaturated solution is any solution
that can dissolve more solute at a given
temperature.

Each time a saturated solution is heated
to a higher temperature, it becomes
unsaturated.

On a solubility chart, any amount of
solute below the line indicates the
solution is unsaturated at that certain
temperature.
Concentration: Supersaturated

A supersaturated
solution is one that
contains more solute
than a saturated
solution at the same
temperature.

Supersaturated
solutions are unstable.

On a solubility chart, •
any amount of solute
above the line in which
all of the solute has
dissolved indicates that
the solution is
supersaturated.
Ex: If a seed crystal of sodium
acetate is dropped into the
supersaturated solution, excess
sodium acetate crystallizes out.
Concentration: Review
UNSATURATED
SOLUTION
more solute can
dissolve
SATURATED
SOLUTION
no more solute
can dissolve
concentration
SUPERSATURATED
SOLUTION
becomes unstable,
crystals form
Conductivity

For specific solutions…

The higher the concentration, the higher the
conductivity of electricity.
 The
higher the concentration, the brighter the light.
Electrolytes

Dissociation

separation of +/- ions
when an ionic
compound dissolves in
water
Electrolytes


Electrolytes: compounds that produce
solutions of ions (cations [positive] or
anions [negative]) that conduct electricity
in water
Examples:

Strong Electrolytes: conduct a strong
current



Most salts, strong acids, strong bases
Ex: NaCl (table salt), hydrochloric acid, sodium
hydroxide
Weak Electrolytes: conduct a weak current


Weak acids and bases
Ex: Acetic acid (vinegar), ammonia, water
Nonelectrolytes

Nonelectrolytes: substances that form no
ions in water and cannot conduct
electricity

Examples:
 Sucrose-
table sugar
 Ethyl alcohol
Electrolytes
-
-
+
salt
-
+
acetic acid
+
sugar
Strong
Electrolyte
Weak
Electrolyte
NonElectrolyte
solute exists as
ions only
solute exists as
ions and
molecules
solute exists as
molecules
only