9/14/2015
2.2 Mixtures >
2.2 Mixtures > Describing Matter
• A salad bar provides a range of items, such as
lettuce, tomatoes, cheese, and green peppers.
Chapter 2
Matter and Change
• Customers choose which items to use in their
salads and how much of each item to use.
2.1 Properties of Matter
• So, each salad mixture has different types and
amounts of components.
2.2 Mixtures
2.3 Elements and Compounds
2.4 Chemical Reactions
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2.2 Mixtures >
– A mixture is a physical blend of two or more
components.
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2.2 Mixtures > Describing Matter
CHEMISTRY & YOU
Why aren't there coffee grounds in a cup
of coffee?
Most samples of matter are mixtures.
• Some mixtures are easier to recognize
than others.
Coffee is often
brewed by mixing
hot water with
ground coffee
beans.
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• You can easily recognize chicken noodle
soup as a mixture of chicken, noodles,
and broth.
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2.2 Mixtures > Classifying Mixtures
Recognizing air as a mixture of gases is
more difficult.
How can mixtures be classified?
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2.2 Mixtures > Describing Matter
Describing Matter
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• But the fact that air can be drier or more
humid shows that the amount of one
component of air—water vapor—can vary.
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9/14/2015
2.2 Mixtures > Describing Matter
2.2 Mixtures > Describing Matter
Homogeneous Mixtures
The substances in the
olive oil are evenly
distributed throughout
the mixture.
Based on the distribution of their
components, mixtures can be
classified as heterogeneous mixtures
or homogeneous mixtures.
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• So, olive oil doesn’t
look like a mixture.
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2.2 Mixtures > Describing Matter
2.2 Mixtures > Describing Matter
Homogeneous Mixtures
Heterogeneous Mixtures
In chicken noodle soup, the ingredients in
the soup are not evenly distributed
throughout the mixture.
The same is true for
vinegar.
• Vinegar is a mixture of
water and acetic acid,
which dissolves in the
water.
• There is likely to be different amounts of
chicken and noodles in each spoonful.
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2.2 Mixtures > Describing Matter
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2.2 Mixtures > Describing Matter
Homogeneous Mixtures
Heterogeneous Mixtures
Olive oil and vinegar
are homogeneous
mixtures.
A mixture in which the composition is not
uniform throughout is a heterogeneous
mixture.
• A homogeneous
mixture is a mixture in
which the composition
is uniform throughout.
• Another name for a homogeneous mixture is a
solution.
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9/14/2015
2.2 Mixtures > Describing Matter
2.2 Mixtures >
Homogeneous Mixtures
At the beach, you realize that both
ocean water and sand are mixtures.
Which is a homogeneous mixture (or
solution)? Which is a heterogeneous
mixture?
Many solutions are liquids.
• But some are gases, like air.
• And some are solids, like stainless steel, which is
a mixture of iron, chromium, and nickel.
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Salt water is a homogeneous mixture, or
solution. Sand is a heterogeneous mixture.
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2.2 Mixtures > Describing Matter
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2.2 Mixtures > Separating Mixtures
Homogeneous Mixtures
Separating Mixtures
The term phase is used to describe any
part of a sample with uniform composition
and properties.
How can mixtures be separated?
• By definition, a homogeneous mixture consists of
a single phase.
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2.2 Mixtures > Describing Matter
2.2 Mixtures > Separating Mixtures
A heterogeneous
mixture consists of two
or more phases.
If you have a salad containing an
ingredient you don't like, you can
remove it with a fork.
• When oil and vinegar
are mixed, they form
a heterogeneous
mixture with two
layers, or phases.
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• The oil phase floats
on the water, or
vinegar, phase.
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• Many mixtures are not as easy to separate.
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2.2 Mixtures > Separating Mixtures
2.2 Mixtures > Separating Mixtures
Filtration
• To separate a mixture of olive oil and
vinegar, for example, you could decant, or
pour off, the oil layer.
The coffee filter at right can
separate ground coffee
beans from brewed coffee.
• Or, you might cool the mixture until the oil
turned solid.
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• The liquid brewed coffee
passes through the paper
filter, but the solid coffee
grounds cannot pass
through the filter.
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2.2 Mixtures > Separating Mixtures
2.2 Mixtures > Separating Mixtures
Filtration
• To separate a mixture of olive oil and
vinegar, for example, you could decant, or
pour off, the oil layer.
Filter paper used in a laboratory is similar
to coffee filters.
• Or, you might cool the mixture until the oil
turned solid.
• Filter paper is often placed in a funnel.
• Then the mixture is poured into the funnel.
– Pouring off the oil layer takes advantage of the fact
that oil floats on water.
• Solid particles that cannot pass through the
filter remain in the funnel.
– Cooling until the oil layer turns solid takes
advantage of a difference in the temperatures at
which the olive oil and vinegar freeze.
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• The rest of the particles pass through.
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2.2 Mixtures > Separating Mixtures
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2.2 Mixtures > Separating Mixtures
Filtration
Differences in physical properties can
be used to separate mixtures.
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The process that separates a solid from a
liquid in a heterogeneous mixture is
called filtration.
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9/14/2015
2.2 Mixtures >
2.2 Mixtures > Separating Mixtures
CHEMISTRY & YOU
Distillation
Brewed coffee is a mixture of ground
coffee beans and water. What process
is used to separate ground coffee
beans from brewed coffee?
The figure below shows an apparatus used to perform
a small-scale distillation.
Filtration is used to separate ground coffee
beans from brewed coffee.
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2.2 Mixtures > Separating Mixtures
Distillation
Tap water is a homogeneous mixture of
water and substances that are dissolved
in the water.
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2.2 Mixtures > Separating Mixtures
Distillation
As water in the distillation flask is heated, water vapor forms,
rises in the flask, and passes into a glass tube in the condenser.
• The tube is surrounded
by cold water, which
cools the vapor to a
temperature at which it
turns back into a liquid.
• One way to separate water from the other
components in tap water is through a
process called distillation.
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• The liquid
water is
collected in a
second flask.
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2.2 Mixtures > Separating Mixtures
2.2 Mixtures > Separating Mixtures
Distillation
Distillation
The solid substances that were dissolved in the water
remain in the distillation flask.
• This is because their
boiling points are much
higher than the boiling
point of water.
During a distillation, a liquid is boiled to
produce a vapor that is then condensed
into a liquid.
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9/14/2015
2.2 Mixtures >
2.2 Mixtures >
Sample Problem 2.1
Sample Problem 2.1
2 Solve Apply concepts to this situation.
Separating a Heterogeneous Mixture
Identify a property that can be used to
separate different substances from each
other.
How could a mixture of
aluminum nails and iron
nails be separated?
• The ability to be attracted by a magnet is a
property that iron and aluminum do not
share.
• You could use a magnet to remove the iron
nails from a mixture of iron and aluminum.
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2.2 Mixtures >
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2.2 Mixtures >
Sample Problem 2.1
1 Analyze Identify the relevant concepts.
Which physical property does
filtration rely on to separate
mixtures? Which does distillation
rely on?
In order to identify how to separate
aluminum and iron nails, the properties of
both aluminum and iron must be known.
Filtration relies on the size of a particle, or
molecule, of a substance. Distillation relies
on the boiling point of the substance.
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2.2 Mixtures >
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2.2 Mixtures > Key Concepts
Sample Problem 2.1
2 Solve Apply concepts to this situation.
List the properties of each substance in
the mixture.
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Aluminum
• metal
• gray color
• doesn’t dissolve
in water
• not attracted to
magnet
Iron
• metal
• gray color
• doesn’t dissolve
in water
• attracted to
magnet
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Mixtures can be classified as
heterogeneous mixtures or as
homogeneous mixtures, based on the
distribution of their components.
Differences in physical properties can
be used to separate mixtures.
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9/14/2015
2.2 Mixtures > Glossary Terms
• mixture: a physical blend of two or more
substances that are not chemically combined
• heterogeneous mixture: a mixture that is not
uniform in composition; components are not
evenly distributed throughout the mixture
• homogeneous mixture: a mixture that is
uniform in composition; components are
evenly distributed and not easily distinguished
• solution: a homogeneous mixture; consists of
solutes dissolved in a solvent
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2.2 Mixtures > Glossary Terms
• phase: any part of a sample with uniform
composition and properties
• filtration: a process that separates a solid
from the liquid in a heterogeneous mixture
• distillation: a process used to separate
components of a mixture using differences in
boiling points
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