6.1
Pure Substances and Mixtures
Page 137
Time
PRESCRIBED LEARNING OUTCOMES
45–60 min
• classify substances as elements, compounds, and mixtures
Key Ideas
KNOWLEDGE
All matter can be classified
as pure substances or
mixtures.
• matter is anything that has mass and volume; it is generally classified
as pure substances or mixtures
• matter is made up of tiny particles (particle model theory)
• mixtures have two or more kinds of particles
Vocabulary
•
•
pure substance
mixture
Skills and Processes
Observing
Interpreting Data
Lesson Materials
per pair
• filter paper
• scissors
• black water-soluble marker
• 250-mL beaker
• water
Program Resources
BLM 0.0-6 Three-Column
Table
SM 6.1 Pure Substances and
Mixtures
Nelson Science Probe 7
Web site
www.science.nelson.com
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Unit B: Chemistry
SKILLS AND ATTITUDES
• demonstrate curiosity, skepticism, creativity, open-mindedness, accuracy,
precision, honesty, and persistence as important scientific attributes
• use appropriate tools and techniques to gather, analyze, interpret, and
share information
SCIENCE BACKGROUND
• Having discussed the classification of
science into many sub-branches (in
the preview), students should readily
understand why chemists must group
all matter. Classifications are often
used in science because grouping
together objects that have things in
common makes it easier for scientists
to compare and contrast them. Matter
can be grouped into two categories:
pure substances and mixtures.
• Mixtures can be homogeneous or
heterogeneous. In homogeneous
(meaning “same kind”) mixtures, the
particles of the pure substance mix
together so completely that the
mixture looks and feels as though it
is only made of one substance.
Homogeneous mixtures are also
called solutions (covered in Section
6.3 of the student book).
Heterogeneous (meaning “different
kinds”) mixtures are those in which
two or more substances can be
seen and felt. Heterogeneous
mixtures are also called mechanical
mixtures (covered in Section 6.3 of
the student book).
• A general rule for classification
systems is given below (Dewey
Classification System). You might ask
students why only a few groups
should be used.
• Most libraries use the Dewey
Classification System for print
matter. In this system, books are
grouped first into broad subject
areas and then into subgroups. Ask
students to find out how this system
works. The Dewey System uses the
following groupings:
• 000 Generalities
• 500 Sciences
• 100 Philosophy
• 600 Technology
• 200 Religion
• 700 The Arts
• 300 Social
Sciences
• 800 Literature
• 400 Language
• 900 History,
Geography
• The Greek philosopher Democritus is
credited with proposing a theory of
atomism (an early form of particle
theory), which states that everything
in the universe is composed of
particles called atoms. (Atoms are
not mentioned by name in the
student book. Atoms are tiny
particles of which all things are
made. Each atom is made up of
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protons and neutrons in a nucleus,
and electrons, which revolve around
the nucleus. Every substance has its
own kind of atom.) Democritus also
stated that there must be spaces
between the atoms (“the void”),
otherwise atoms could not move.
• Democritus’ theory remained
unchanged until about the 17th
century. From this point on,
scientists such as John Dalton,
George Thomson, Ernst Rutherford,
Niels Bohr, and others further
developed the particle theory.
TEACHING NOTES
1 Getting Started
• Check for Misconceptions
– Identify: Students may think that a mixture and a compound are
the same, and the terms can be used interchangeably.
– Clarify: Discuss the meanings of these terms with students.
A compound is a substance made up of different elements (pure
substances that cannot be broken down) joined together. For
example, water is a compound, made up of the elements oxygen
and hydrogen. Compounds can be separated into elements or
simpler compounds by breaking these chemical bonds. A mixture
is a substance that contains different elements and compounds that
are not joined chemically (by chemical bonds). For example, the
air we breathe is a mixture. It contains elements, such as oxygen
and nitrogen, and some compounds, such as carbon dioxide.
– Ask What They Think Now: Ask students to list two things that are
mixtures and two things that are compounds. Have them justify
their answers. Engage the class in a discussion.
• This section introduces the method that chemists use for classifying
matter. Ensure students know that all matter is made up of particles.
There are many different kinds of particles. Different substances
have different properties because they contain different kinds of
particles. The particles of one pure substance are different from the
particles of other pure substances.
• Emphasize that everything is made of particles (the desk, a pencil, a
goldfish, students, and so on). Encourage students to visualize that
everything around them is made of particles.
• Tell students that they will learn to classify matter into pure
substances and mixtures. Ask students to define classification.
Finding out what students already know can determine both your
emphasis and your approach to this section. Classification means
putting things into groups. The groups in a classification system may
be based on observable differences (properties that you can see), or
on any other predetermined criteria.
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Chapter 6
Matter can be classified.
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2 Guide the Learning
• This section’s main purpose is to introduce the concept of pure
substances and mixtures. As with mixtures, the key criteria for
distinguishing pure substances are properties. Students might record
the meaning of pure substance along with several examples (some are
provided). A pure substance is a substance that contains only one
kind of particle.
• Ask students how they would classify the following items: cement,
orange juice, chocolate drink mix, milk, plastic from a plastic bag,
ink, etc. Everyday examples of pure substances (in the above list,
only plastic is a pure substance) could be added to students’
notebooks. All of the other substances are mixtures.
• Use models to illustrate pure substances and mixtures. You may use
different colours of modelling clay to illustrate Figure 3.
• In this section, students should begin a graphic organizer, similar to
the one on page 138. Use Reading and Thinking Strategies:
Synthesize.
• Use Try This: Test Ink to show students that ink, which looks like a
pure substance, is actually a mixture. This activity illustrates a
procedure called chromatography, which is a method of separating
materials out of a mixture. Ink is actually a mixture of several dyes,
and the colours can be separated using chromatography. The
banding pattern produced as the ink creeps up filter paper is called a
chromatograph.
• Chromatography has many uses; it can be used to help doctors
diagnose diseases; it can be used in forensic science; and it can also
be used to purify chemicals.
• For students who need additional support with reading in this
section, use SM 6.1 Pure Substances and Mixtures.
TRY THIS: TEST INK
Purpose
• Students will observe what happens as the water soaks into the filter paper.
Notes
• Ensure that all students try the activity so that they can see firsthand how the
ink creeps up the filter paper.
• The marker used in this activity must be water soluble.
• Coffee filters can be used in the place of filter paper.
Suggested Answers
• Answers may vary. In general, the ink will creep up the filter paper. There should
be different bands of colour produced because the black marker is made from a
number of different dyes. The different bands of colour show that ink is a mixture.
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Unit B: Chemistry
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At Home
3 Consolidate and Extend
• Review the terms classification, pure substances, and mixtures.
• Provide students with a number of materials, including mixtures
such as fruit punch, trail mix, table salt and sand, oil and vinegar
salad dressing, and yogurt, and pure substances such as aluminum
foil, sugar, salt, and iron. Ask students to identify whether each is a
pure substance or a mixture on BLM 0.0-6 Three-Column Table.
• Ask students, Is pure water a pure substance? (Yes.) Is methanol a pure
substance? (Yes.) How about sodium chloride? (Yes.) We cannot tell
from the name of a material (long or short, common language or
chemical name) whether or not it is a pure substance or a mixture.
Sand, for example, is a short word, but it is a mixture. Sodium
chloride might sound like a mixture, but is actually a pure substance.
Again, we must use properties such as density, hardness, melting
point, freezing point, and boiling point to distinguish pure
substances.
• Assign the Check Your Understanding questions.
CHECK YOUR UNDERSTANDING—SUGGESTED ANSWERS
1. Pure substances contain only one kind of particle, whereas mixtures contain
two or more pure substances. Examples of pure substances include pure water
and diamond. Examples of mixtures include soft drinks and bread.
2. Pure substances have only one kind of particle. Pure substances contain the
same type of particle throughout. Mixtures have two or more pure substances
mixed together and, therefore, contain a number of different types of particles.
In mixtures, there may be more or less of the different kinds of particles. For
example, the air you breathe is a mixture. It contains elements, such as oxygen
and nitrogen, and compounds, such as carbon dioxide.
3. Student answers may vary. Examples of pure substances include aluminum foil,
table sugar, and table salt. Examples of mixtures include orange juice, cement,
and milk.
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Chapter 6
Ask students to explain to
family members why
classification is important.
Have students ask their
families if they can think of
two other classifications
they use every day.
Students should look for
examples of classifications
used at home (e.g., the
cutlery drawer in the
kitchen, the linens in the
linen closet, nails and
screws in the workshop,
canned goods in the
grocery cupboard, etc.).
Math Connections
Discuss why classification
in mathematics is
important. We classify
numbers according to
factors (prime and
composite). We classify
polygons according to the
number of lines of
symmetry they have.
Triangles are classified
according to the measure
of their angles or the
number of equal sides.
Quadrilaterals are
classified according to
pairs of parallel sides,
congruent sides, and right
angles.
Matter can be classified.
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Reading and Thinking Strategies: Synthesize
LEARNING TIP
Before you read this
chapter, begin a graphic
organizer that shows how
different types of matter
can be classified. The first
level in your organizer will
look like the diagram to the
right. As you work through
this chapter, add more
levels to your organizer.
MATTER
PURE SUBSTANCES
MIXTURES
All samples of a pure substance have the same properties, no
matter what size the samples are or where in the world the samples
are found. For instance, all samples of pure gold have the same
melting and boiling points and the same density. Because every
sample of a pure substance has the same properties, scientists have
made reference lists of pure substances and their properties. These
reference lists can help you to identify an unknown substance based
on its properties.
Mixtures
Almost all the natural substances and manufactured products in the
world are mixtures of pure substances. A mixture contains two or
more pure substances, as shown in Figure 3.
pure substance
• Sometimes it is helpful for students to make a graphic
organizer as they study new information. Before they
read this chapter, ask students to begin a graphic
organizer or a mind map that explains how different
types of matter can be classified. The first level in the
organizer will look like the diagram on page 138 of the
student book. As students work through this chapter,
they will add more levels to their organizer. Tell them
that making a graphic organizer can help them
summarize information in a way that will help them to
remember it. Ask them to continue their organizer in
Sections 6.2 and 6.3.
mixture
pure substance
Figure 3
Most substances that you encounter are mixtures. Mixtures contain at least two
pure substances.
Mixtures can be any combination of
solids, liquids, and gases. For example,
soft drinks are mixtures made from
liquid water, solid sugar, and carbon
dioxide gas (Figure 4).
Figure 4
Soft drinks may look like pure substances, but they
are mixtures.
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Unit B
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Meeting Individual Needs
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Extra Support
• Use the diagrams to aid comprehension for students who find reading
science content a challenge.
• For students who need additional support with reading in this section,
use SM 6.1 Pure Substances and Mixtures.
ESL
• Have students who have difficulty with the language draw diagrams of
the vocabulary terms and/or observations. Students can add items to
their visual dictionaries.
• Prepare and maintain a vocabulary list for the classroom on chart
paper, using visual representations where possible.
ASSESSMENT FOR LEARNING
What To Look For in Student Work
Suggestions for Teaching Students Who Are Having Difficulty
Evidence that students can
• explain how all matter can be classified as
pure substances or mixtures
• interpret observations (e.g., test ink)
• use technical language correctly
(pure substance, mixture)
Use examples that are familiar to students.
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Unit B: Chemistry
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