Solutions
Chapter 22
Sections 1 - 4
Solutions
Section 1 How Solutions Form slides 3-14
Section 2 Solubility & Concentration slides
15-28
Section 3 Particles in Solution slides 29-38
Section 4 Dissolving Without Water slides
39-49
1 How Solutions Form
What You’ll Learn:
Three types of solutions
How things dissolve
The rate solids and gases dissolve
What is a solution?
A solution is a mixture that has the same
ingredients, color, density, and even taste
mixed evenly throughout.
You can’t see the sugar crystals because
they have broken up into molecules that
mix with water molecules and food
coloring.
Solutes and Solvents
The solute is the substance that
dissolves.
The solvent is the substance that is doing
the dissolving.
In sugar-water, sugar is the solute and
water is the solvent.
What can dissolve in a liquid?
In a solution made with a liquid & a solid,
the solid is the solute & the liquid is the
solvent. Which is which in salt water?
What can dissolve in a liquid?
In a solution made with a liquid & a solid,
the solid is the solute & the liquid is the
solvent. Which is which in salt water?
Some solutions are gas dissolved in a
liquid like carbonated soda in which
carbon dioxide is dissolved in water.
What can dissolve in a liquid?
In a solution made with a liquid & a solid,
the solid is the solute & the liquid is the
solvent. Which is which in salt water?
Some solutions are gas dissolved in a
liquid like carbonated soda in which
carbon dioxide is dissolved in water.
Other solutions have a liquid dissolved in
another liquid like food coloring in water
with the solvent being the one present in a
larger amount.
Are there solutions that do not contain a
liquid?
 Solutions can be mixtures of gases or
even mixtures of solids.
Air 78% N, 20% O, etc of other gases
Sterling silver is a mixture of silver & copper, a
solid solution or alloy is melted together
Brass is copper & tin
How Substances Dissolve
A solid starts to dissolve at its surface.
Water molecules are always moving and
they are polar. Polar means they have a
positive end and a negative end. Sugar is
also polar so that the positive ends of the
sugar molecules attract the negative ends
of the water molecules. The water pulls
the sugar into solution removing layer after
layer of sugar until the crystal is dissolved.
How do liquid & gas solutions form?
It is similar but more complex because
liquids and gases move much faster than
solid particles.
The movement separates the solute
particles and mixes them evenly in the
solvent resulting in a homogeneous
solution.
How do solids dissolve in other solids?
 Solids must be melted into liquids & then mixed
together.
 In the liquid state, atoms move more freely to
spread and form a homogeneous solution which
stays even after cooling.
Rate of Dissolving:
 Can be increased by
stirring or heating.
Increases particle
speed
 If the solute is a solid
you can break it into
smaller pieces.
Increases surface area
Can you combine these methods?
o The rate of dissolving
increases with each
additional method you
use.
2 Solubility & Concentration
What You’ll Learn:
What solubility is
About the concentration of solutions
Three types of solutions
Factors that affect gas solutions
How much can dissolve?
Solubility is the greatest amount of solute
that can dissolve in a specific amount of
solvent at a given temperature.
How much can dissolve?
Solubility is the greatest amount of solute
that can dissolve in a specific amount of
solvent at a given temperature.
The difference of solubilities of solutes
depends on the nature of the solute and
the nature of the solvent.
How much solute is in a concentrated
solution?
 Concentration may be
stated as a
percentage by volume
of the solute.
 A drink with 10
percent fruit juice has
10 mL of juice in 100
mL of the drink.
Types of Solutions
 You can use the
amount of solute
dissolved to describe
3 different types:
Saturated
Unsaturated
supersaturated
What is a saturated solution?
A saturated solution is one that contains
all the solute it can hold at a given
temperature.
If you increase the temp of the mixture,
more solute can dissolve.
As shown in the following table, the
solubility of solid solutes increases as the
temperature of the liquid solvent
increases.
Solubility of Compounds
in g/100 g of Water
compound
0°C
20°C
100°C
Copper(II) sulfate
23.1
32.0
114
Potassium
bromide
53.6
65.3
104
Potassium
chloride
28.0
34.0
56.3
Potassium nitrate
13.9
31.6
245
Sodium chlorate
79.6
95.9
204
Sodium chloride
35.7
35.9
39.2
Sucrose (sugar)
179.2
203.9
487.2
What is a solubility curve?
 Each line on the
graph is a solubility
curve for a
substance.
 To find how much of a
substance dissolves
at a particular temp,
find the temp on the
x-axis & trace the line
upward to the curve
for that substance.
What is an unsaturated solution?
www.sunflowerlearning.com/images/di.gif
 An unsaturated
solution can dissolve
more solute at a given
temperature.
 An unsaturated
solution can have any
amount of copper (II)
sulfate less than 32 g
in 100 g of water at
20°C.
How can a solution be supersaturated?
 Honey is naturally a
supersaturated
solution.
 A supersaturated
solution has more
solute than a saturated
solution at the same
temperature. These
solutions are unstable
& may crystallize w/
any addition of solute.
When do solutions give off energy?
Supersaturated sodium acetate solution
becomes hot as sodium acetate
crystallizes. Sometimes when bonds form,
energy is given off in the form of heat.
Some heat packs are filled with a
supersaturated solution that gives off heat
as the solute crystallizes.
When do solutions give off energy?
Some solutes take energy from their
surroundings to dissolve. As a result, the
temperature of the solution is reduced.
Ammonium nitrate is an example. A cold
pack has inner bags of water & ammonium
nitrate. A solution forms when the inner
bags are broken; energy is drawn from the
water as the solution forms causing the
temperature to drop thus the pack feels
cool.
Solubility of Gases
Soda is a solution of carbon dioxide gas
dissolved in flavored water. When you
shake an open bottle of soda, it bubbles.
Shaking or stirring a solution of a gas in a
liquid allows more gas molecules to reach
the surface of the liquid, where they
escape into the air.
How do pressure & temperature affect a
gas dissolved in a liquid?
Soda is bottled under a great amount of
pressure to force more gas to dissolve in the
soda & to keep the gas in solution.
When you open the can, the pressure is
released & bubbles of gas come out of
solution.
Cooling a liquid increases the amount of gas
that will dissolve in it (opposite of solids).
Warm soda bubbles more than cold.
3 Particles in Solution
What You’ll Learn:
How some solutes form positively or
negatively charged particles
How some solutions conduct electricity
How antifreeze works
Particles with a Charge
A particle with a charge is an ion. Ions are
throughout your body in fluids helping
nerve cells send messages controlling
your muscles.
An electrolyte is a compound that
produces solutions of ions that conduct
electricity in water. Strong electrolytes,
like NaCl dissolve completely into ions,
conduct a strong electric current.
Particles with a Charge
Weak electrolytes, like acetic acid in
vinegar, stay mainly as molecules when
they dissolve in water, produce only a few
ions and conduct current weakly.
Nonelectrolytes are substances that do
not form ions in water and cannot conduct
electricity. Organic molecules like sucrose
(sugar) and ethyl alcohol are examples.
How do ionic solutions form?
Ionization, the process of forming ions,
happens when molecules are broken apart
so that the atoms take on a charge.
Polar molecules divide into ions, ex. HCl &
waterH3O+ (hydrogen ion in water)
The separation of ionic compounds into positive
and negative ions is called dissociation. The next
slide shows what happens to NaCl as it dissociates
with H drawn to Cl & Na to O due to opposite
charges.
Sodium & Chloride Ions Mixed w/ Water
Effects of Solute Particles
 All solute particles can affect physical properties
of a solvent, such as freezing point & its boiling
point.
How does antifreeze lower the freezing
point?
As a substance freezes, its particles
arrange themselves in an orderly pattern.
Solute particles interfere with this pattern
making it harder for the solvent to freeze.
A lower temperature is needed to freeze
the solvent.
Why can some animals live in a cold
climate?
Caribou have substances in their bodies
that keep their legs from freezing.
Fish also have a natural kind of antifreeze
that keeps ice crystals from forming in
their tissues.
Many insects have a similar chemical to
protect them.
How can the boiling point of water be
raised?
Antifreeze also raises the boiling point of
water by interfering with the evaporation of
solvent particles.
More energy is needed for the solvent
particles to escape from the liquid
surfaces.
The more solute particles in the solution,
the higher the boiling point of the solution
will be.
How does antifreeze work in a car
radiator?
Solute particles block part of the surface
so fewer water molecules can reach the
surface & vaporize.
The solution cannot boil because the
vapor pressure of the solution is lower
than the vapor pressure of the solvent.
Added energy is required to raise the
vapor pressure & make it boil.
4 Dissolving Without Water
What You’ll Learn:
What solutes do not dissolve in water
How polar and nonpolar solvents work in
water
How to choose the right solvent for
cleaning
When Water Won’t Work
There are some things, such as salad
dressing with vinegar and oil, that water
cannot dissolve.
Water molecules dissolve polar solutes but
not most nonpolar ones without positive &
negative areas.
How do nonpolar solutes behave?
Salad oils are made of large hydrocarbon
molecules which share electrons in a
nearly equal way. These nonpolar oil
molecules are not attracted to polar water
molecules. This is also why you have to
shake oil and vinegar dressing to mix it
before using it.
Why are alcohols special?
 Molecules of some
substances have a
polar end and a
nonpolar end so they
can form solutions
with polar and
nonpolar solutes.
 This is ethanol with
an OH group that’s
polar & the rest which
is nonpolar.
It can dissolve both nonpolar iodine
and polar water.
Useful Nonpolar Molecules
Mineral oil can be used to remove candle
wax from candleholders, bubble gum from
some surfaces.
To remove wet paint or make it thinner use
turpentine.
Gasoline is a solution of different
hydrocarbons.
Dry cleaners use nonpolar solvents.
Remember “like dissolves like”.
When are nonpolar solvents not helpful?
Many nonpolar solvents are flammable or
burn easily.
Some are toxic & should never be used in
a closed room.
They evaporate readily so you must
always have fresh air when using them.
How does soap work?
 Natural oils on your
skin and hair keep
them from drying out,
but they also attract
and hold dirt in a
nonpolar mixture.
You need to use soap
with both polar and
nonpolar properties to
wash it away.
How does soap work?
 Soaps start out as
large fatty acid
molecules with long
hydrocarbon ends
that are nonpolar. A
carboxylic acid group,
COOH, is at the other
end. Without the H
atom, the end has a
negative charge.
How does soap work?
 The ionic end of a
soap molecule
dissolves in water.
The nonpolar end
dissolves in oily dirt.
Together the two ends
of a soap molecule
remove dirt so it can
be rinsed away.
Polarity & Vitamins
 Vitamin A from liver,
lettuce, cheese, eggs,
carrots, sweet
potatoes, and milk
can dissolve in body
fat because both are
nonpolar. Fat-soluble
vitamins can be very
harmful at high
concentrations.
 Polar vitamins, such
as B & C dissolve in
the water in your
body. Excess
vitamins wash away.
Eat a healthful diet to
avoid harmful
overdose.