6.3
Mixtures
Page 144
Time
PRESCRIBED LEARNING OUTCOMES
45–60 min
• classify substances as elements, compounds, and mixtures
Key Ideas
KNOWLEDGE
Mixtures can be classified
as mechanical mixtures,
suspensions, or solutions.
• matter is anything that has mass or volume; it is generally classified as
pure substances or mixtures
• changes to matter can be reversible (mixtures and changes of state) and
non-reversible (mechanical change such as grinding, chemical change
such as cooking)
• matter is made up of tiny particles (particle model theory)
• mixtures have two or more kinds of particles
• mixtures can be classified as solutions, suspensions, or mechanical
mixtures
• suspensions consist of solid particle pieces scattered throughout the
mixture
• solutions are mixtures that appear as a single substance
Vocabulary
•
•
•
•
mechanical mixture
suspension
emulsion
solution
Skills and Processes
Observing
Predicting
Creating Models
Lesson Materials
per student
• 2 clear plastic containers
(plastic graduated
cylinders)
• marbles
• washable marker or grease
pencil
• sand
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
• develop models to represent systems or analogies about matter
Program Resources
SM 6.3 Mixtures
Science Skills and Processes
Rubric 1: Creating Models
Science Skills and Processes
Rubric 2: Creating
Models—Self-Assessment
Nelson Science Probe 7
Web site
www.science.nelson.com
ICT OUTCOMES
• work cooperatively using information technology tools
• use a variety of information technology tools to create, modify, explore,
and present electronic documents that express ideas or concepts
• synthesize information from a variety of electronic sources for
presentations
• apply the principles of good design when developing electronic documents
• develop interactive hypertext documents for presentations
SCIENCE BACKGROUND
• Almost all of the substances in the
world, natural as well as humanmade and manufactured products,
are mixtures of pure substances.
• A mixture is a substance made up of
different elements and compounds.
As mentioned before, the elements
and compounds are not joined
chemically (no chemical bonds).
Mixtures can be separated by
physical or mechanical means.
• Mixtures are further classified as
mechanical mixtures (e.g., sooty air,
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salad, cornflakes and milk, concrete),
suspensions (e.g., muddy water,
tomato juice, farm-fresh milk) or
solutions (e.g., clean air, vinegar, tea,
flat cola, clear shampoo).
• Colloids, not covered in the student
book, are another kind of mixture,
with properties between that of a
solution and a suspension. The
suspended particles in a colloid are
very small, smaller than those in a
suspension, and the particles are
evenly distributed and will not settle
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out the way they do in a suspension.
Examples of colloids are fog, cheese,
butter, jellies, and whipped cream.
• Homogeneous mixtures are uniform
throughout; heterogeneous mixtures
do not have a uniform composition.
• Particle sizes distinguish
homogeneous mixtures from one
another.
• Solutions have particles between
0.2 and 1.0 nm (nanometres).
• Colloids have particles between
2.0 and 1000 nm.
• Suspensions have particles greater
than 1000 nm.
• When two liquids mix, they are said
to be miscible. Alcohol and water are
miscible. When two liquids do not
mix, they are said to be immiscible.
Water and oil are immiscible.
Related Resources
Darling, David. From
Glasses to Gases, The
Science of Matter.
Toronto: Dillon Press,
1992.
TEACHING NOTES
1 Getting Started
• Check for Misconceptions
– Identify: Students may think that mixtures and solutions are the
same.
– Clarify: Discuss the differences with students. Mixtures are
substances made up of different elements and compounds.
Mixture is an umbrella term for mechanical mixtures, suspensions,
and solutions. Solutions are mixtures formed when a solid, liquid,
or gas dissolves in another solid, liquid or gas. Mixtures can be
classified by appearance.
– Ask What They Think Now: Ask students how they would classify
mixtures according to their appearance. Finding out what students
already know can determine both the emphasis and approach to
this section.
• Ask students to skim the section and predict how many kinds of
mixtures there are. Use Reading and Thinking Strategies:
Predict/Anticipate.
• Have students brainstorm different ways to classify mixtures using
appearance. Write their answers on chart paper and post for
discussion. Students may suggest state, colour, density, size of
particles, etc.
2 Guide the Learning
• Reflection of light by suspended particles is called the Tyndall effect,
named after the scientist John Tyndall.
• Set up a small introductory demonstration to observe the Tyndall
effect, using a small box, two jars of water, one teaspoon of flour, a
spoon, a flashlight, and scissors.
– Cut a small, square viewing hole in the front of the box. The hole
must be close to the corner of the box and as high as the jar of
water. Poke a small hole with the tip of the scissors in the end of
the box (as high as the jar of water). Add flour to only one of the
jars of water, and stir. Place a jar inside the box near the viewing
square opening. Shine the flashlight into the small poked hole with
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Chapter 6
Matter can be classified.
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the flashlight. Observe the contents of both of the jars through the
viewing hole.
– The glass of flour and water looks brighter than the glass with
water only. The reason is that the flour and water formed a
suspension. Light strikes the floating particles of flour in the water
and is reflected, or bounced back. The water without the flour
does not reflect light. Inform students that the flour floating in the
water is a suspension. Ask students if they have seen other liquids
that have similar qualities.
• Next show the class some granola, a glass of tomato juice, and a glass
of saltwater from the ocean. Ask students how they would classify
these items. Have students write their responses in their notebooks.
– Granola is a mechanical mixture. In a mechanical mixture you can
easily see two or more parts of the mixture.
– Tomato juice is a suspension. In suspensions, such as tomato juice,
solid pieces are scattered throughout a liquid.
– Saltwater is a solution. In saltwater (sea water), the substances are
so completely mixed that they look like one substance.
• Emulsions are dispersions of one liquid in a second immiscible
liquid. When a salad dressing of oil and vinegar is shaken up, an
emulsion is made. When emulsions are shaken, the droplets of oil
get very small and become scattered uniformly throughout the
vinegar. Sometimes, emulsifying agents are used to stabilize a
mixture and ensure that it does not separate.
• Have students examine some examples of solutions, mechanical
mixtures, suspensions, and emulsions, and describe them using key
vocabulary terms.
• Mayonnaise is an emulsion. The two immiscible liquids are oil and
vinegar (or lemon juice). The emulsifying agent in mayonnaise is egg
yolk.
• Emulsions have many applications in medications, photography,
paints, and food production.
• Ensure that students understand that solutions can be liquids, gases,
or solids. Brass is a solution of copper and zinc. Steel is a solution of
iron, oxygen, and carbon.
• For students who need additional support with the reading in this
section, use SM 6.3 Mixtures.
• Have students complete Try This: Model a Solution.
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TRY THIS: MODEL A SOLUTION
Purpose
• Students will make a model to show how particles mix in a solution.
Notes
• Ensure that all students try the activity so that they can see firsthand how
particles mix in a solution.
Suggested Answers
• Predictions may vary.
• In general, the sand will fill the space between the marbles, giving the
appearance of only one substance. If you gently shake the graduated cylinder,
you can see that the particles of sand and marble are not so completely mixed
that they cannot be seen. If it were a true solution, it would be so completely
mixed that the parts would not be visible, even under a microscope.
3 Consolidate and Extend
• Review the terms mechanical mixtures, suspensions, and solutions with
students.
• Use Table 1 in the student book as a review.
• When students go home, ask them to look around their homes to
find two or three examples of mechanical mixtures, suspensions,
emulsions, and solutions. Compile a master list of these different
types of mixtures.
• Assign the Check Your Understanding questions.
CHECK YOUR UNDERSTANDING—SUGGESTED ANSWERS
1. Student answers may vary. Mechanical mixtures include yogurt with fruit, stir-fry
of different vegetables, pizza, Jell-O with fruit, etc. Solutions include contact
lens solution, window cleaner, soda, etc.
Technology Connections
2. a) Green relish is a mechanical mixture. Two or more parts can be seen with
the unaided eye (chunks of pickle, jelly).
b) Freshly squeezed orange juice is a suspension. It is a cloudy mixture in which
clumps of a solid or droplets of liquid are scattered throughout the liquid.
c) Soda pop in a glass is a solution. It appears to be only one substance.
d) Bubble tea is a mechanical mixture. Two or more parts can be seen with the
unaided eye (tapioca bubbles, tea).
e) Trail mix is a mechanical mixture. Two or more parts can be seen with the
unaided eye (nuts, raisins, seeds, etc.).
f) Traditional Aboriginal paint, made of red ochre and grease, is a suspension.
It is a cloudy mixture in which clumps of a solid or droplets of liquid are
scattered throughout the liquid.
g) Vegetable soup is a mechanical mixture. Two or more parts can be seen with
the unaided eye (carrots, celery, potatoes, broth).
3. Similarities between suspensions and solutions: both are mixtures that appear to be
one substance; they’re usually liquids, but they can also be gases and solids.
Differences between suspensions and solutions: suspensions, if not stirred, may
separate into layers; solutions are so completely mixed that particles cannot be
seen.
Have students work on
their own or with a partner
using a computer graphics
program to create a
graphic organizer that
illustrates how matter is
classified. Once students
have created their graphic
organizers, they can add
appropriate text to define
each term used and
explain the characteristics
of each classification. This
activity can be extended
by using a hypertext
computer program that
allows students to add
illustrations and
animations to their
explanations.
4. You get 1175 mL of drink rather than 1250 mL, because the crystal particles
slide in between the particles of water to fill in the spaces between the particles
of water, reducing the total volume produced. This is an example of a solution.
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Reading and Thinking Strategies:
Predict/Anticipate
Mechanical Mixtures
A mechanical mixture is a mixture in which two or more different
parts can be seen with the unaided eye. Granola cereal is an example
of a mechanical mixture (Figure 2). Concrete is another example.
Before reading the section, ask students to skim through
the section and predict how many categories of mixtures
there are. Students should be able to do this by looking at
the subheads in the section. After they have read the
section, have students comment on how their findings
from the reading match their predictions.
Figure 2
This cereal is a mechanical mixture.
What other foods can you classify
as mechanical mixtures?
Suspensions
A suspension is a cloudy mixture in which clumps of a solid or
droplets of a liquid are scattered throughout a liquid or gas. Muddy
water and tomato juice are suspensions. The parts of a suspension
may separate into layers if the suspension is not stirred.
Farm-fresh milk is a suspension. If the milk is left standing,
the fatty part (the cream) floats to the top and the watery part sinks
to the bottom (Figure 3). Commercially available milk does not
separate. It is a special kind of suspension, called an emulsion,
which has been treated to keep it from separating. In a process
called homogenization, the milk is sprayed through very small
openings. This breaks down the fat into droplets that are so tiny
they stay suspended.
Figure 3
Cream floats to the top of farmfresh milk.
6.3
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Meeting Individual Needs
Mixtures
145
Extra Support
• Ensure that students work in mixed-ability groups so they can support
each other with their individual strengths.
• For students who need additional support with the reading in this
section, use SM 6.3 Mixtures.
ESL
• Encourage students to participate. They may require a scribe to note
their observations.
Extra Challenge
• Have students find the definition for the term emulsion and find out
more about how homogenized milk is produced using emulsification.
• Have students conduct research to find other common examples of
emulsions (examples given earlier—in medicine, paint, foods).
Students should be able to explain why emulsification is important in
these applications and how the emulsions are produced.
ASSESSMENT FOR LEARNING
What To Look For in Student Work
Suggestions for Teaching Students Who Are Having Difficulty
Evidence that students can
• describe how mixtures can be classified
• make predictions (e.g., volume when you
combine marbles and sand)
• interpret observations (e.g., model how
particles mix in a solution)
• use technical language correctly
(mechanical mixture, suspension,
emulsion, solution)
Have students review the section with a resource person. Review vocabulary and
terms in the previous sections. Use familiar examples.
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