Curriculum Topic Study: Mixtures and Solutions
FOSS kit: Mixtures and Solutions
Curriculum Topic Study
SCED 480
Laura Holzer, Ashley Stone, and Meagan Follett
Big Ideas: (adapted from Page 1 of FOSS kit mixtures and solutions)
 Gain experience with the concepts of mixture and solution, concentration and saturation, and chemical reactions.
 Apply an operational definition to determine the relative concentrations of solutions.
 Use group problem solving techniques to plan investigations, measurement in the context of scientific investigations, and
scientific thinking processes to conduct investigations and build explanations. (Observing, communicating, organizing,
comparing, and relating).
 Apply mathematics in the context of science.
 Acquire vocabulary associated with chemistry and the periodic table.
Identify Adult
Content
Knowledge
What enduring understanding should all adults, including
teachers, know about this topic (Keeley, 37)?
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“…everything is really made up of a relatively few
kinds of basic material combined in various ways”
(SFAA, 46).
“When two or more substances interact to form
new substances (as in burning, digestion, corrosion,
and cooking), the elements composing them
combine in new ways… The basic premise of the
modern theory of matter is that the elements consist
of a few different kinds of atoms—particles too tiny
to see in a microscope—that join together in
different configurations to form substances. There
are one or more—but never many—kinds of these
atoms for each of the approximately 100 elements.
There are distinct patterns of properties among the
elements” (SFAA, 47).
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These first two quotes emphasize the
importance for adults to understand how
atoms are constructed and how they connect
to form elements. This knowledge is
important background information for
understanding why solutions interact in
certain ways. This big idea is not explicitly
represented in the Mixtures and Solutions
FOSS kit. Instead, the FOSS kit facilitates
and supports the notion that kids need to
experience things firsthand and see what
chemical reactions look like on a meaningful
level. The knowledge gained through the
FOSS kit investigations may serve as a base
for learning about atoms and the structure of
matter in later years. However, it is important
that instructors understand the big picture so
that they can effectively guide and make
connections for students.
“The arrangement of the outermost electrons in an
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This third quote is specifically important
atom determines how the atom can bond to others
and form materials…Depending on what kinds of
bonds are made, the atoms may link together in
chaotic mixtures, in distinctive molecules that have
a uniform number and configuration of atoms or in
the symmetrically repeated patterns of crystal
arrays” (SFAA, 48).
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The rates at which reactions occur in large
collections of atoms depend on how often the
reactants encounter one another—and so depend on
the concentration of reactants and how fast they are
moving (that is, on temperature)… In particular,
reactions occurring in water solution may be
affected significantly by the acidity of the solution”
(SFAA, 48-49).
because it strongly correlates with the
observing crystals section in the FOSS kit. It
is essential for adults and teachers to
understand how atoms are constructed so that
they can understand how crystals are formed
in order to effectively to support students’
inquiry and learning.
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We feel that this quote is quite relevant to the
Mixtures and Solutions FOSS kit. Once you
understand this idea you can understand
many different areas of science. This
information is specifically relevant to this
FOSS kit in relation to saturation and
concentration of solutions and how they
impact chemical reactions. It is essential for
teachers to be confident in their knowledge
of this topic so that they can successfully
facilitate student learning. If teachers
understand this information, they can take
this knowledge and pose thought provoking
questions to students in order to promote
inquiry based learning. Inquiry learning will
help students internalize knowledge about
molecular structures, which is an abstract
idea to students. Teachers need to know this
information to successfully lead students’
inquiry.
Examine
Research on
Student Learning
What specific misconceptions or alternative ideas might a
student have about this topic (Keeley, 38)?
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Mixtures & Solutions
“Most of the materials children encounter in
everyday life are mixtures and therefore, from a
science viewpoint, cannot be regarded as ‘pure’.
However, some materials (such as air, water,
honey, yogurt, and other foods) are frequently
labeled ‘pure’, although they are really mixtures of
substances” (Driver, 74).
“The tendency for pupils to regard everyday
materials as single substances was evident in an
interview study where many 15-year-olds were
unable to give examples of mixtures or explain
them. Children could more readily recognize
heterogeneous mixtures, such as granite, than
homogeneous ones, such as solutions” (Driver, 74).
“Children do not always appreciate that their
statements about the properties of a mixture are of
little value unless they state the composition of the
mixture too” (Driver, 74).
“Other children, because they did not see a
boundary between solute and solvent, regarded a
solution as a single substance rather than as a
homogeneous mixture” (Driver, 84).
“[Holding] asked five groups of pupils to place
some sugar in water and stir the mixture until the
sugar could no longer be seen. He then asked them
to draw their idea of what was ‘there’…The
majority of children depicted ‘bits of sugar’
distributed in several ways without drawing the
water….The next most prevalent picture of a
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Mixtures & Solutions
Some of children’s misconceptions of
science terminology are brought into the
class with them. Words such as ‘pure’ have
connotations of being ‘clean’ or ‘untainted’.
Students see substances such as yogurt as
pure because it is seen as ‘purely yogurt’.
Students must relearn some terminology
from a science perspective, to understand that
words can have different meanings in
everyday life and in a science context. FOSS
addresses these misconceptions in
investigation 1 part 1 where students
differentiate between a mixture and solution;
students make and separate mixtures of water
and solid materials. They discover that water
and salt make a special kind of mixture: a
solution, which cannot be separated with a
filter. In investigation 1 part 4 students
separate a dry mixture using the techniques
of filtering and evaporation.
Even adults confuse the idea of solvents and
single substances. We do not often think of
substances such as Pepsi as a solution; rather
we see it as a single substance. The students
we teach have similar misconceptions, it is
important to confront these misconceptions
with hands on experience. The FOSS kit
addresses these misconceptions; in
investigation 1 part 2, students separate salt
solution was ‘continuous’ shading throughout…
Molecules were rarely mentioned in the earlier
years but later an appreciable proportion depicted
‘molecular particles’ of sugar – at age 15 and age
17 – but only half of these pupils also depicted
molecules of water. It would appear that a
continuous view of water is still quite prevalent in
older pupils’ thinking about solutions (Driver, 95).”
from a water solution.
Concentration & Saturation
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“…there are several conceptions of
‘dissolving’…Up to age 8, there is a tendency to
focus on the solute only and say it ‘just goes’,
‘disappears’, melts away’, ‘dissolves away’, or
‘turns into water’….Frequently, older pupils
imagine that as sugar dissolves it ‘goes into tiny
little bits’. Later on some say that ‘sugar molecules
fill spaces between water molecules’ or else ‘mix
with water molecules’” (Driver, 83).
“…when probed about the weight of the solution,
only about 50 percent of those who said the sugar is
‘there’ also say that ‘it weighs something’” (Driver,
84).
Concentration & Saturation
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As stated earlier, students experience
difficulty with differentiating science
vocabulary from everyday vocabulary. In
order for students to understand that there are
actual parts (atoms and molecules) within a
substance, they must experience various
substances first hand. One way to experience
this is through experiments. Students are
able to physically ass a solute into a solvent
(such as salt into water) before they will ever
understand concentration and saturation of
water. Students take their understanding to
the next level, in investigation 2 part 1
students learn that a solution is saturated
when as much solid material (such as salt)
has dissolved in the liquid as possible.
Investigation 2 part 3 requires students to
experiment with an unknown material
(Epsom salts) which leads to an
understanding that solubility is the property
that substances have of dissolving in
solvents, and solubility is different for
different materials and can change with
temperature and different solvents.
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“After age 8, pupils increasingly generate more
ideas about the kind of changes they imagine the
solute undergoes…However, they do not regard
weight as a gravitational force acting on the
‘bits’…After age 12, many pupils begin to develop
a gravitational view of weight and also a science
conception of mass so that eventually many, but by
no means at all, conserve both weight and mass of a
solute” (Driver, 84).
“Although some students may think that
substances can be divided up into small particles,
they do not recognize the particles as building
blocks, but as formed of basically continuous
substances under certain conditions” (Atlas, 336).
“Although some 3rd graders may start seeing weight
as a fundamental property of all matter, many
students in 6th and 7th grade still appear to think of
weight simply as “felt weight”—something whose
weight they can’t feel is considered to have no
weight at all” (Atlas, 336).
Chemical Reactions
“By 5 grade, many students can understand
qualitatively that matter is conserved in
transforming from solid to liquid. They also start to
understand that matter is quantitatively conserved
in transforming from solid to liquid and
qualitatively in transforming from solid or liquid to
th
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These three quotes address students’
misconceptions about weight; students tend
to believe that if they cannot see of feel
something, then it does not have weight. This
misconception has to be addressed before the
weight of solutions can be understood. This
concept is important to understanding that all
things are made up of some kind of material.
For example students don’t think that air has
weight, but air is not just blank space, it is
made up of atoms and molecules that do
indeed have weight. The FOSS kit first
introduces the concept of weight in
investigation 1 part 2 when they separate salt
from the water solution; they compare the
total mass of the mixture from the mass of its
parts. Then in investigation 2 part 2 students
compare the solubility of salt and citric acid
by comparing the mass solid materials
dissolved in the saturated solution.
Chemical Reactions
Once students have gained an understanding
of concentration they are prepared to move
on to chemical reaction experiments.
Investigation 4 focuses on chemical reaction
experiments with the ultimate goal of
teaching students they can apply techniques
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Examine
Coherency and
Articulation
gas –if the gas is visible. For chemical reactions,
especially those that evolve or absorb gas, weight
conservation is more difficult for students to grasp”
(Atlas, 337).
“Middle—and high-school student thinking about
chemical change tends to be dominated by the
obvious features of the change…further, many
students do not view chemical changes as
interactions. They do not understand that
substances can be formed by the recombination of
atoms in the original substances. Rather, they see
chemical change as the result of a separate change
in the original substance, or changes, each one
separate, in several original substances” (Atlas,
337).
“They lack an appreciation of the very small size of
particles; attribute macroscopic properties to
particles; believe there must be something in the
space between particles; have difficulty in
appreciating the intrinsic motion of particles in
solids, liquids, and gases; and have problems in
conceptualizing forces between particles” (Atlas,
337).
of separating mixtures and solutions to
chemical reactions. In the investigation
students mix combinations of solid materials
with water and observe the changes that
occur; they identify changes such as gas, and
white precipitate as evidence of chemical
reactions. They use the techniques of filtering
and evaporating that they acquired in
previous investigations to separate and study
the products of reactions. Students conduct
chemical reaction experiments in closed
systems such as Ziploc bags, which enable
them to observe the gas more critically.
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In the FOSS kit investigation 2 part 4 the
students observe and compare citric acid and
salt crystals and learn that crystals have
specific shapes and patterns. Through
observations students will gain an
understanding of how the specific shape of
individual atoms and molecules is a smallscale version of the large-scale crystals they
have made.
What pre-requisite ideas can you identify for learning the
topic at your grade level (Keeley, 39)?
The following points are from the Atlas of Science
Literacy web of student understanding, found on page 57.
K-2:
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“Objects can be described in terms of the materials
 These concepts are key in laying the
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3-5:
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6-8:
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they are made of.”
“Things can be done to materials to change some of
their properties, but not all materials respond the
same way to what is done to them.”
Most things are made of parts.”
“People can keep track of some things, seeing
where they come from and where they go.”
“Some features of things may stay the same, even
when other features change.”
groundwork towards understanding mixtures
and solutions. Students must understand that
“things are made up of parts” and “objects can
be described by the materials they are made of”
to understand the basic concepts of mixtures and
solutions. In the FOSS curriculum, students
work with examining large scale manipulatives
to build an understanding pf smaller scale
unseen particles.
“No matter how parts of an object are assembled,
the weight of the whole object is the same as the
sum of the parts.”
“Substances may move from place to place, but
they never appear out of nowhere, and the never
just disappear.”
 Weight can be a tricky concept for kids,
especially when they cannot see a substance, of
the parts of a whole. Understanding the sum of
an objects parts and that all substances are
constant is integral to understanding mixtures
and solutions. If students mix together salt and
water they must understand that the salt is still
‘there’ and it still has weight.
“No matter how substances within a closed system
interact, the total mass of the system remains the
same.”
“All matter is made up of atoms, which are far too
small to see directly through a microscope.”
“The idea of atoms explains the conservation of
matter; if the number of atoms stays the same no
matter how the same atoms are rearranged, then
their total mass stays the same.”
 Once students understand the concepts
outlined for K-5th graders, they have laid the
groundwork for understanding more abstract
concepts such as mass, atoms, and molecules.
These higher-level concepts are not addresses
directly in the FOSS kit, but those lessons do
address the pre-requisite knowledge that must
be gained at the younger grades in order to
move on to these concepts.
References
Key
American Association for the Advancement of Science, National Science Teachers Association. (2001). Atlas of
Science Literacy. Washington D.C.
American Association for the Advancement of Science. (1993). Benchmarks for Science Literacy. New York,
Oxford: Oxford University Press.
American Association for the Advancement of Science. (1990). Science For All Americans. New York, Oxford:
Oxford University Press.
Driver, R., Squires, A., Rushworth, P., & Wood-Robinson, V. (1994). Making Sense of Secondary Science.
London and New York: Routeledge Falmer.
Keeley, P. (2005). Science Curriculum Topic Study. Thousand Oaks, California: Corwin Press.
Atlas= Atlas of Science Literacy
Benchmarks= Benchmarks for Science Literacy
FOSS= Full Option Science System
SFAA= Science for all Americans