Solutions
Key Terms
 Suspension
 Colloid
 Emulsion
 Solution
 Solute
 Solvent
 Alloy
Any sample of matter is either a pure substance or a mixture
of pure substances
Heterogeneous Mixtures
The amount of each substance in different samples of a
heterogeneous mixture varies
Particles in a suspension are larger and eventually settle out
Suspension is a mixture in which particles of a material are
more or less evenly dispersed throughout a liquid or gas.
Particles in a suspension may be filter out.
Particles in suspensions are usually the size of or
larger than the tip of an extremely sharp
pencil.
Particles of this size are large enough that they can
be filtered out of the mixture.
You can classify a mixture as a suspension if the
particles settle out or can be filtered out.
Some mixtures of two liquids will separate.
The two liquids separate because they are immiscible.
Meaning they do not mix.
In order to separate two immiscible liquids we can pour the
less dense liquid of the top by a process called decanting .
Particles in a colloid are too small to settle out
Colloid is a mixture consisting of tiny particles that are
intermediate in size between those in solution and those in
suspension and that are suspended in a liquid, solid, or gas.
What is the Tyndall effect?
It is the scattering of light though a colloid mixture
Other familiar materials are also colloids
The particles in most colloids are composed of many atoms,
ions, or molecules, but individual protein molecules are
also large enough to form colloids.
Some immiscible liquids can form colloids
Mayonnaise is a colloid consisting of very small droplets of
oil suspended in vinegar.
Mayonnaise is an emulsion
An emulsion is a colloid in which
liquids that normally do not mix are spread
throughout each other.
Like other colloids, an emulsion has
particles so small that it may appear to be
uniform.
Homogeneous Mixtures
Homogeneous mixtures not only look uniform but
are uniform.
Homogeneous mixtures are solutions
Solutions are homogeneous mixtures of two or
more substances uniformly dispersed throughout a single
phase.
Solute in a solution, the substance that dissolves in
the solvent
Solvent in a solution, the substance in which the
solute dissolves
Mixtures are homogeneous when the smallest particles
of one substance are uniformly spread among similar
particles of another substance.
All homogeneous mixtures are also solutions
Miscible liquids mix to form solutions
Two or more liquids that form a single layer when
mixed are said to be miscible
How can we separate miscible liquids?
By a process call distillation. Distillation works
only when the two miscible liquids have different
boiling points.
Liquid solutions sometimes contain no water
What are some examples of liquid solutions that do
not contain water?
1. Nail-polish remover
2. paint strippers
3. gasoline
Other states of matter can also form solutions
Solutes and solvents can be in any state.
Solids can dissolve in other solids
Alloy is a solid or liquid mixture of two or more
metals.
The mixing of solids is when they are in a liquid
state then turned back into a solid.
Alloys are important because they have properties that the
individual metals do not have.
Not all alloys contain metals. Some types of steel are alloys
containing the nonmetal element carbon
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a. homogeneous b. homogeneous
c. heterogeneous d. heterogeneous
Particles in a suspension are larger than those in a colloid. As a
result, the particles in a suspension settle out and can be
filtered out, but those in a colloid do not settle out an cannot
be filtered out.
Air, Mixtures of gases, dental amalgam, sterling silver, brass,
bronze, and other metal alloys
Water is the solvent and baking soda or sodium hydrogen
carbonate is the solute.
Sugar water, egg white, muddy water
Distillation can separate liquids that have different boiling
points. The boiling points of formic acid and water are too
close together for separation by distillation.
Show her that the drink is sweet which is evidence that the
sugar is still present. Allow the water to evaporate, showing
that the crystalline sugar is regained, although contaminated
with the drinking flavoring.
Key Terms
 Polar Compound
 Hydrogen Bonding
 Nonpolar Compound
Water: A Common Solvent
Two-thirds of Earth’s surface is water and
three-fourths of your body weight is
water. Many different substances can
dissolve in water. For this reason water
is sometimes called the universal
solvent.
Water can dissolve ionic compounds
because of its structure
Polar Compound is a molecule that
has an uneven distribution of electrons.
A polar molecule has a distinct
positively and negatively charged side.
Water molecules attract both the
positive and negative ions of an ionic
compound.
Polar water molecules pull ionic crystals
apart.
Dissolving depends on forces between
particles
To dissolve an ionic substance,
water molecules must exert a force on
the ions that is more attractive than the
force between the ions in the crystal.
This is true for all solvents
Water dissolves many molecular
compounds
Water has a low molecular mass,
but it is a fairly dense liquid with a
high boiling point. Water has these
properties because of hydrogen
bonding.
Besides ionic compounds, water also
dissolves many molecular compounds,
such as ethanol, ascorbic acid, and table
sugar.
Like dissolves like
A rule of thumb in chemistry is that
like dissolves like. For example, water is a
polar molecule because it has positive and
negative ends. So, water dissolves ions and
polar molecules, which also have charges.
Nonpolar Compounds are
compounds whose electrons are
equally distributed among its
atoms. Usually will not dissolve in
water.
The Dissolving Process
Remember that molecules are always
moving (Kinetic theory of Matter).
Since the molecules are always moving
they are colliding with each other and
other objects. As the molecules of a
solvent collide with a solute the solute
begins to dissolve.
Solutes with a larger surface area
dissolve faster
Stirring or shaking a solution helps the
solute dissolve faster
Solutes dissolve faster when the solvent
is hot
Solutes affect the physical
properties of a solution
By adding sodium chloride to water
you can increase the boiling point
and also lower the freezing point
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Water is a polar molecule, which means that one end has
slight positive charge and the other end has a slight
negative charge. These charged ends are attracted to
opposite charges on the other polar molecules, such as
methanol and to charged ions in ionic substances, such
as ammonium chloride. As a result water molecules can
pull polar molecules and ions into solution.
Solvents can dissolve a substance only if the attraction of
the solvent molecules for the particles of the substance is
greater than the attraction between the particles of the
substance.
The larger crystals of salt have less surface area exposed
to water than the same mass of smaller crystals.
Therefore, more sodium and chloride ions are attracted
by water molecules at the surface of the smaller crystals.
Water will dissolve glycerol because the polar water
molecules attract the polar groups of glycerol and
pull it into solution.
5. Raising the temperature of the water, shaking, or
stirring the mixture would increase the rate of
dissolving of the salt.
6. The presence of a solute lowers the freezing point of
a solution below that of the pure solvent. So, the
freezing point of the drink mix is lower than that of
water, and the drink mix has not become cold
enough to freeze, although that water has.
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Key Terms
 Solubility
 Concentration
 Unsaturated Solution
 Saturated Solution
 Supersaturated Solution
 Molarity
Remember that not all substances dissolve in water. If a
substance does not dissolve it is said to be insoluble.
Solubility in Water
As you know substance are not soluble in water. However,
substance that are soluble in water have a limit to how
much of the substance will dissolve in water. The
maximum amount of substance that will dissolve in water
is called solubility.
Solubility is the maximum amount of a solute that will
dissolve in a given quantity of solvent at a given
temperature and pressure.
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Example:
The maximum amount of salt that can be dissolved
in 100g of water at room temperature is 36g.
There are some substances that are completely soluble in
water. This means no matter how much you add it will all
mix with water to form a solution.
Some ionic compounds, such as silver chloride (AgCl), are
almost completely insoluble in water.
Different substances have different solubilities (Table 1 pg
240).
Even closely related compounds can have very
different solubility. The solubility of a compound
depends on the forces acting between water molecules
and solute particles compared to the forces acting
between the solute particles
Concentration is the quantity of solute dissolved in a given
volume of solution. If the solution contains a large amount
of solute it is concentrated. If there is only a small amount
it is dilute.
Unsaturated solutions can dissolve more solute
An unsaturated solution is a solution that contains less
solution than a saturated solution does and that is able to
dissolve more solute.
At some point, most solution become saturated with
solutes
Once a solution becomes saturated with solutes it is no
longer able to dissolve the solute.
Saturated solutions cannot dissolve any more solute
under the given conditions
Heating a solution usually dissolves more solute
saturated
So by changing the given conditions, we are able to
dissolve more solute into a solution. This cause the
solution to become a supersaturated solution.
A supersaturated solution is a solution that is holding more
dissolved solute than is required to reach equilibrium at a given
temperature.
What happens to the solute when the temperature decreases?
The solute will remain in solution until something is added to
cause the solute to dropout. The solute will continue to fall out
until the solution is saturated at the cooler temperature.
Temperature and pressure affect the solubility of gases
Concentration of Solutions
Describing a solution as concentrated, dilute, saturated, or
unsaturated still does not reveal the quantity of dissolved
solute.
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Some substances are only slightly soluble in water. For
example, only 0.32g of calcium sulfate dissolves in 100g of
water. Such a solution is saturated because it contains the
maximum amount of solute, but still dilute because it
contains only a little solute per unit volume.
The solution can be heated and additional solute
dissolved. When the solution is cooled to the original
temperature, it will be supersaturated.
By adding small amounts of salts we can determine if the
saltwater is unsaturated, saturated, or supersaturated. If
it dissolves, the solution is unsaturated. If it remains
undissolved, the solution saturated. If new crystals form
in the solution, the solution is supersaturated.
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Acetic acid is completely soluble in water, while olive oil
is completely insoluble in water. The solubility of olive oil
is zero, and the solubility of acetic acid is effectively
infinite.
Evaporation would take place faster at 37% humidity
because the solution of water vapor in air is less
saturated than it is at 92% humidity.
0.5 M
Gases such as nitrogen and oxygen, from the air are
dissolved in the cold water. Gas solubility decreases with
increasing temperature, so the dissolved gas has come
out of solution, forming bubbles as the temperature of
the tap water increases.