Physical Science—Chemistry/Introductory Physics*
Concept and Skill Progressions
Sequenced concepts and skills to support student learning of science and
technology/engineering from PreK to high school, informed by preconception, conceptual change, and learning progression research
Massachusetts Department of Elementary and Secondary Education
November 15, 2010
* Please note there are corresponding documents available for:
Earth and Space Science
Life Science—Biology
Technology/Engineering
The concept and skill progressions are meant to inform and support curriculum and instruction,
but are not meant to replace the current Science and Technology/Engineering (STE) standards.
Curricular and instructional goals should continue to be aligned with current STE standards;
the state’s STE MCAS tests will also continue to reference current STE standards.
November 15, 2010
Table of Contents
Section
Page
Introduction to the Concept and Skill Progressions
2
Visual organization of the Concept and Skill Progressions (Figure 1)
4
Physical Science—Chemistry/Introductory Physics Concept and Skill Progressions**
Force & Motion
5
Conservation & Transformation of Energy
10
Matter & Its Transformations
17
Atomic Structure & Periodicity
29
Chemical Bonding & Reactions
35
Solution Chemistry
44
Contributors:
Dr. Alicia C. Alonzo, Michigan State University, Michigan
Dr. Muammer Çalık, Karadeniz Technical University, Trabzon, Turkey
Dr. Jazlin Ebenezer, Wayne State University, Michigan
Dr. Arthur Eisenkraft, University of Massachusetts, Boston, Massachusetts
Dr. David Fortus, Weizmann Institute, Israel
Dr. Phil Johnson, Durham University, England
Dr. Alan Kiste, University of Michigan, Michigan
Dr. Jim Minstrell, A.C.T. Systems for Education, Washington
Dr. Hannah Sevian, University of Massachusetts, Boston, Massachusetts
Shawn Stevens, University of Michigan, Michigan
Dr. David Treagust, Curtin University, Australia
Dr. Stamatis Vokos, Seattle Pacific University, Washington
Dr. Marianne Wiser, Clark University, Massachusetts
** There is not a concept and skill progression for every topic typically found in state Physical
Science—Chemistry/Introductory Physics standards; authors were only available for the six
topics included. **
1
November 15, 2010
Introduction to the Concept and Skill Progressions
This document presents concept and skill progressions for six common Physical Science—
Chemistry/Introductory Physics topics. These concept and skill progressions articulate idealized
sequences of concepts and skills that can effectively support student learning of core scientific
ideas from PreK to high school. These summaries draw from a variety of research genres,
including pre-conception, conceptual change, and learning progression research on science
education. These summaries are written and reviewed by educational researchers who study
student learning of each science and technology/engineering (STE) topic. They are set up to
reflect a learning progression approach to student understanding of core STE ideas. These are
research-based resources that can inform work in curriculum development, instruction, and
assessment. These are also have been referenced, in conjunction with the many other available
STE resources, by the Massachusetts STE Review Panel in the revision of Massachusetts STE
student learning standards.
Learning progression research is beginning to provide a framework for understanding student
preconceptions, obstacles to learning, and transitional ideas about the world as they learn
science. A learning progression makes explicit the successively more complex ways of thinking
about STE concepts and skills that students develop over time (Smith, Wiser, Anderson, &
Krajcik, 2006). While learning progressions are research-based, they are hypothetical; they
propose how to bridge the intuitive ideas children have developed about core ideas before formal
instruction with the scientific version of that idea if students are exposed to appropriate curricula
(Corcoran et al, 2009). Additionally, ideas in learning progressions are not always scientifically
accurate. For example, the idea that any piece of matter, however small, has weight is not
completely scientifically accurate as it only applies to matter in a gravitational field. It belongs in
the learning progression, however, because it makes the idea that atoms are the key components
of matter easier to accept (students often believe that weight is not a property of matter, and if a
piece of material gets very small it has no weight). Considering student cognition from a learning
progression basis allows us to take students’ initial ideas into account, to characterize productive
transitional ideas, and to design curricula that move students' network of ideas toward scientific
understanding in a purposeful way.
The Massachusetts Department of Elementary and Secondary Education has asked educational
researchers to draw from the research literature on students’ pre-conceptions, conceptual change,
and, where available, learning progressions to provide up-to-date summaries of how to sequence
student thinking and learning of common STE topics. The research base to complete this task is
certainly not complete, so for the grade ranges, domains, and/or concepts for which learning
progression research is not available, each author used available pre-conception and conceptual
change research to provide informed estimates of what a progression of learning is likely to look
like. So while the authors have made informed recommendations about when certain concepts
and skills should be introduced, these do not limit what or when students can learn those
concepts and skills. These are idealized articulations of how we would want students to progress.
The concept and skill progressions do, however, help to convey how to move young children’s
initial conceptualizations to scientific theory over time.
2
November 15, 2010
Each concept and skill progression includes both a “narrative storyline” as well as a “concept
and skill details” section that are intended to convey a story of how students’ conceptual growth
can develop over time. Both sections tell the same story, just at different levels of detail. Each
concept and skill progression is organized to reflect the nature of initial ideas in a topic (lower
anchor); the 'stepping stones' that can serve as intermediary targets between initial ideas and
scientific theory; and specify the scientific core ideas, concepts and skills in that domain students
should achieve as the result of their education (upper anchor). It is important to note that each
grade-span cell in the details section should be read in its entirety; the individual concepts and
skills should be viewed as a set rather than individually. See Figure 1 on page 4 for more details
on the organization of the summaries. Providing a common template across topics allows
curriculum developers, educators, and others to make sense of particular core ideas, concepts and
skills in relation to each other across grade levels and topics. It is important to be clear that the
individual elements in the concept and skill progressions are not standards; taken together they
describe what students can know and do over time as they come to learn core scientific ideas.
These concept and skill progressions can be used in conjunction with the 2001/2006 STE strand
maps (http://www.doe.mass.edu/omste/maps/default.html; modeled on the AAAS Atlases of
Science Literacy) to visualize student learning over time. Productively building upon
relationships between ideas that span multiple grade levels will require greater communication
and coordination than is currently typical. Teaching that honors progressions of learning will also
require educators to clearly understand where their students currently are relative to desired
outcomes. This can be accomplished with pre-assessment strategies—including strategies that
move beyond simple identification of misconceptions—as well as greater differentiation of
lessons to meet the needs of particular students. Being able to access a variety of instructional
and learning resources, such as through the National Science Digital Library (NSDL;
http://strandmaps.nsdl.org/), will help educators implement these strategies. Coordinated use of
strand maps will help educators approach teaching and learning from a perspective where ideas
are consistently related to each other over extended periods of time. Such an approach can
effectively account for student conceptions and more effectively promote achievement of science
and technology/engineering standards.
Please note: Topics included in this document were selected based on both available research
and the availability of an author to write the summary. In some cases research is available but an
author was not, or some common concepts within a topic were omitted due to lack of a research
base; these are not exhaustive summaries. These concept and skills progressions will likely be
updated in the future as additional research and information is available. Please direct any
comments, feedback, resources or research that may inform edits or additions to these concept
and skill progressions to mathscitech@doe.mass.edu.
References
Corcoran, T., Mosher, F., Rogat, A. (2009). Learning Progression in Science: An evidence-based
approach to reform. Philadelphia, PA: Consortium for Policy Research in Education.
Smith, C.L., Wiser, M., Anderson, C.W., Krajcik, J. (2006). Implications of research on
children’s learning for standards and assessment: A proposed learning progression for
matter and the atomic molecular theory. Focus Article. Measurement: Interdisciplinary
Research and Perspectives, 14, 1-98.
3
Possible misconceptions, placed in the grade span
before they are addressed, are highlighted gray.
Read concept and skill detail section from left to right, from initial
ideas (pre-instruction) to culminating scientific ideas (high school).
Page 1:
Narrative
storyline
provides an
overview of
how student
ideas develop
across grade
spans.
Page 2+:
Concept and
skill detail
section (pg 2 &
3 of this
example)
provide specific
concepts by
core idea (rows)
and grade-span
(columns).
Stepping
stones move
students from
initial ideas to
scientific
understanding
(read each
grade-span cell
in its entirety).
Key
vocabulary
is indicated
in the grade
span it is
introduced.
Endnotes on
final page(s)
include
comments on
particular
concepts,
including
instructional
strategies, limits
to student
understanding,
and additional
explanation.
Figure 1. Features of the concept and skill progressions, using Plate Tectonics as an example.
4
Force and Motion
November 15, 2010
Force and Motion
Concept and Skill Progression for Force and Motion
This progression traces conceptual changes in children’s ideas about ways the motion of objects can be described and the effect of forces on motion. Students’ understanding of
motion proceeds from qualitative descriptions of everyday encounters with moving objects to increasingly complex models that employ mathematical representations (e.g., graphs,
force diagrams, equations) and general principles (e.g., Newton’s laws) to describe, predict and explain the motion of objects, and account for the range of forces acting on them.
NARRATIVE STORYLINE
Initial Ideas
Before instruction children hold many ideas about the motion of objects that are consistent with scientific ideas. 1 They recognize that some action is required to start an object in
motion and have a sense of the effect of pushing and pulling on objects. However, children also hold ideas about force and motion that are inconsistent with the physicist’s view of the
world.2 Students often believe force is a property belonging to an object, rather than an interaction between two objects; heavier objects exert more force than lighter objects and all
objects will slow down without a force to keep them moving.
Conceptual Stepping Stones
Early Elementary students can qualitatively describe the motion of objects in terms of speed and direction; distinguish between constant and changing motion, and associate
changes in motion with pushes and pulls. Students may continue to believe that force is only exerted by objects that are in direct contact with the object they are affecting, and that the
amount of motion is proportional to the amount of force.
Later Elementary students can recognize that some forces act at a distance and that force does not always act in the direction of motion. Students may continue to believe that there
are “active” and “passive” objects and that all objects eventually slow down without a force to keep them moving.
Middle School students can recognize that all objects can exert a force during an interaction of objects, identify friction as a mechanism by which one object exerts a force on
another, and recognize that more than one force may be acting upon an object. Students can effectively apply these ideas to describe and analyze one-dimensional motion.
Culminating Scientific Ideas
High School students can describe, analyze and model the motion of objects. They also understand Newton’s three laws of motion and recognize that these govern the behavior of all
objects.3 Students can identify the forces acting in both idealized and real-world situations of interacting objects. These situations include those involving objects at rest and in
linear motion, including uniform circular motion.
Massachusetts Department of Elementary and Secondary Education
Force and Motion
5
Force and Motion
November 15, 2010
Lower Anchor
Reflective of student concepts
Force and Motion
Upper Anchor
Reflective of science concepts
Reconceptualization
CONCEPT & SKILL DETAILS
Initial Ideas
Conceptual Stepping Stones
Culminating Scientific Ideas
Before instruction, students often believe
and can:
Students who view the world in this way believe and can:
Students who fully understand this topic
believe and can:
Pre-instruction
K-2
3-5
6-8
High School
Describing motion
Describing motion
Describing motion
Describing Motion
Children observe and expect that
objects move in consistent ways, unless
something acts to change their motion.
For example, after viewing an object
moving in a straight line at a constant
speed, infants make predictions
consistent with the belief that the object
will continue moving at the same speed
and in the same direction (Gopnik, et
al., 1999; von Hofsten, et al., 1998).
Students can describe motion
(qualitatively) in terms of
speed and direction.4
Describing the motion of objects
Effect of forces on motion
Effect of forces on motion
Effect of forces on motion
Effect of forces on motion
Effect of forces on motion
Children know some action is required
to start an object in motion.
Children associate changes in
motion with pushes/pulls.
Students identify pushes and
pulls as forces.8
Children know from experience that
actions are involved when an object at
rest starts to move (a particular instance
of a change in motion):
 If an object is pushed/pulled in a
particular direction, it will often
start to move in that direction.
 Not all objects will move when
they are pushed/pulled.
 More push/pull is required to get a
heavy object moving; less
push/pull is required to get a light
object moving.
Possible misconceptions:
Students may believe that
force is only exerted by
“active” objects6 which are in
direct contact with the object
they are affecting (Halloun &
Hestenes, 1985; Minstrell,
n.d.).
Students associate changes in
motion with forces.
Students identify friction as a
mechanism by which one
object exerts a force on
another. Friction acts in a
direction parallel to the
surface that is exerting the
friction force and always acts
to decrease an object’s
speed.11
Students can represent
constant motion and changing
motion (speeding up, slowing
down, reversing direction) on
distance-time and positiontime graphs.5
Students can distinguish
between constant and
changing motion.4
Students believe that the
amount of motion is
proportional to the amount of
force (Champagne, et. al.,
Students recognize that some
forces (i.e., magnetic,
gravitational, and electric)9act
at a distance.
(Link to gravitational,
magnetic, and electrical
forces.)
Students identify weight as a
force due to gravity.10
Massachusetts Department of Elementary and Secondary Education
Recognize that more than one
force may be acting upon an
object.
Recognize that if an object’s
motion is not changing in
Students understand Newton’s three
laws of motion and recognize that
these govern the behavior of all
objects.13 In particular:
 Every object in a state of uniform
motion remains in that state of
motion, unless an external net
force is applied to it and changes
its direction or speed.
 A change in motion of an object is
proportional to the applied force
and inversely proportional to the
mass.
 Whenever one object exerts a
force on another, an equal amount
of force is exerted back on the
object in the opposite direction.
Students recognize forces are always
due to an interaction between objects,
which can be represented as a force on
object A exerted by object B and a
force on object B exerted by object A.
Students can identify the forces14
acting in both idealized and real-world
situations, with objects at rest and in
linear motion.15
Force and Motion
6
Force and Motion

More push/pull is required to make
an object move quickly; less
push/pull is required to make an
object move slowly.
Possible misconceptions:
Children may believe that force is a
property that belongs to an object,
rather than an interaction between two
objects (Reiner, et. al., 2000); heavier
objects exert more force than lighter
objects (Ioannides & Vosniadou, 2001).
November 15, 2010
1980). 7 Therefore, motion
requires a force in the
direction of motion.
Students often believe weight
is a property of an object.
(Link to earth & space
science.)
Students recognize that force
does not always act in the
direction of motion.
Possible misconceptions:
Students believe that all
objects eventually slow down
without a force to keep them
moving (Halloun &
Hestenes, 1985).
Force and Motion
response to an applied force,
another force must be acting
on the object in the opposite
direction.12
.
Students recognize that both
“active” and “passive”
objects7 can exert a force
(Champagne, et. al., 1980).
Students can represent forces
acting on an object as arrows
(vectors) on an isolated
picture of the object (a force
diagram).
Represent and analyze idealized and
real-world situations using force
diagrams and position-, velocity-, and
acceleration-time graphs.
Qualitatively and quantitatively
describe, analyze, and represent the
motion of objects, including constant
and changing motion as well as
uniform circular motion16 when
provided with information about the
forces acting upon them.17
Grades
Pre-instruction
K-2
3-5
6-8
High School
friction, frame of reference,
position-time graph, distancetime graph
Newton’s Laws, normal force, circular
motion, force diagram, net force,
velocity-time graph, acceleration-time
graph
Key Vocabulary
motion, speed
force, weight, gravity
Notes
(1) Even infants have developed expectations about the behavior of moving objects (e.g., Gopnik, Meltzoff, & Kuhl, 1999, pp. 66-67; von Hofsten, Vishton, Spelke, Feng, &
Rosander, 1998).
(2) This can be attributed to a number of different factors, including:
 Everyday experiences are over-generalized – for example, ideas about objects starting to move are over-generalized to apply to any moving object.
 Words (such as “force”) have different meanings in the everyday world than they do in the specialized language of physics (e.g., Halloun & Hestenes, 1985)
 Experiences in the everyday world are influenced by the ubiquitous force of friction.
(3) LIMIT: These laws apply to “all” motion students will typically experience; these do not directly apply in, nor do we do not expect students to extend them to, relativistic,
nano, or quantum physics.
(4) Students at this age have many experiences with moving objects to draw upon; however, they will need tools (such as ways to represent motion) in order to recognize patterns
of motion (describing in terms of both speed and direction and characterizing motion by either constant or changing speed and/or direction).
(5) LIMIT: Analysis of interactions is expected for one dimension only. Forces are limited to the same dimension but may be in different directions. To effectively graph motion
students need to be able to describe motion relative to an observer or chosen point of reference.
(6) Although students would be unlikely to use such language, “active” and “passive” may be considered roughly similar to “animate” and “inanimate”. Students often think that
living things (such as people, but not necessarily plants) can exert forces, but that nonliving things (such as tables or walls) cannot (Halloun & Hestenes, 1985; Minstrell, n. d.).
(7) These seemingly simple statements contain a number of component ideas. For example, the idea that motion is proportional to force contains the following misconceptions:
Massachusetts Department of Elementary and Secondary Education
Force and Motion
7
Force and Motion
November 15, 2010
Force and Motion







If there is motion, there is a force acting (Clement, 1982; Ionnides & Vosniadou, 2001).
If there is no motion, there is no force acting (Halloun & Hestenes, 1985; Gilbert & Watts, 1983; Minstrell, n. d.)
If there is a force, there is motion (Champagne, Klopfer, & Anderson, 1980).
If there is no force, there is no motion (Champagne, Klopfer, & Anderson, 1980).
A constant speed results from a constant force (diSessa, 1983; Champagne, Klopfer, & Anderson, 1980; Gilbert & Watts, 1983; Halloun & Hestenes, 1985; Minstrell, n. d.).
Acceleration requires a constantly changing force (Champagne, Klopfer, & Anderson, 1980; Halloun & Hestenes, 1985; Minstrell, n. d.).
When an object slows down, it is because the force is being used up; it stops when the force is all gone (Halloun & Hestenes, 1985; McCloskey, 1983; Trumper & Gorsky,
1996).
Typically, each of these component ideas is treated as a separate misconception; however, each of the misconceptions is related to an overall idea about how the world works.
Rather than addressing each misconception individually, an overall idea is articulated.
(8) In expressing ideas about force and motion, students often use “force” to mean something more like the physicist’s definition for momentum. Making the distinction between
everyday uses of the word “force” and the physicist’s definition may help students to build upon intuitive ideas about motion (which tend to be correct, if “momentum” were
substituted for “force”).
(9) Students typically learn about electricity and magnets in elementary school. However, the idea of magnetic forces is seldom connected to the idea of mechanical forces. Ideas
about forces acting at a distance require such connections to be made.
(10) Students’ initial beliefs about falling, gravity, and weight should be included in earth and space science. Students often struggle to see gravity as the same as other types of
forces. Yet, we often use gravity as an example–and then assume that students understand more general ideas about forces because they have understandings related to gravity.
For example, students who can very clearly explain acceleration due to gravity (for falling objects) persist in the belief that forces cause motion (as opposed to changes in
motion). While some students explain this by saying that gravity increases close to the earth’s surface, many students see no inconsistency because they do not recognize
gravity as the same as other forces. Students should develop ideas about force and motion first and then add gravity as an example – rather than using gravity to build
understandings related to force and motion. Students can readily learn that magnetic (and electrostatically charged) objects exert forces across space (although the students
might wonder if the air has anything to do with it). Magnetic and electrostatic forces can be used through analogy to build a case for gravitation also being a force which “acts at
a distance.” In all three cases, the force exerted is determined by both a property of the objects (electrostatic charge, pole strength, or mass) and the distance between the
objects.
(11) To reduce dissonance between students’ everyday experiences and the ideas being taught, friction must be introduced and used as a means of explaining “real world” behavior
of objects. Be careful not to label gravity or friction as forces, as these are mechanisms by which one object exerts a force on another; these do not exert the forces, they just
identify the mechanism.
(12) At this level, students are expected to consider only one-dimensional motion. In this case, a force acting in the opposite direction would be required. However, for motion in
two- or three-dimensions, the requirement is only for there to be a force which has a component in the opposite direction. (For example, a force at a 45 degree angle to the
original force would be possible.) Students must realize that the interaction between two objects in contact with each other stops as soon as the objects stop touching and that
any forces which result from the contact interaction are no longer acting. Students will often believe, for example, that a ball tossed into the air is moving because of the force of
the person’s throw (Alonzo & Steedle, 2009; Ionnides & Vosniadou, 2001).
(13) While specific competencies noted below are required in order to achieve the broad, conceptual statements included here, too often, “plug & chug” or rote identification of
Newton’s laws are seen as evidence of student understanding of these concepts; instead, these concepts are intended to put discrete competencies in the context of larger
conceptual goals. The types of interactions of the objects and force laws involved must be identified in order to use Newton’s laws to explain and predict the motion of an object
or system.
(14) The “normal force” just tells a direction, but the use of the term can lead students to think of that as the thing that is exerting the force and they forget about the force that the
surface exerts, the force that is perpendicular to the surface.
(15) This should include mathematical representations of both kinetic and static friction.
(16) Motion is limited to straight-line motion (horizontally, up and/or down an incline, or vertically) and to uniform circular motion. Since motion is linear, the sign determines the
direction for all vector quantities.
Massachusetts Department of Elementary and Secondary Education
Force and Motion
8
Force and Motion
November 15, 2010
Force and Motion
(17) Students will need to be able to make reasonable simplifying assumptions to gain a basic understanding of a situation or interaction or to solve a problem (e.g., “massless”
ropes, “frictionless” sliding surfaces, “negligible” air resistance). Quantitative descriptions and analysis include distance and displacement, speed and velocity, and acceleration.
Authors and Reviewers
Dr. Alicia C. Alonzo, Michigan State University, Michigan (author)
Dr. Jim Minstrell, A.C.T. Systems for Education, Washington (reviewer)
References
Alonzo, A. C., & Steedle, J. T. (2008). Developing and assessing a force and motion learning progression. Science Education, 93, 389-421.
American Association for the Advancement of Science. (1993). Benchmarks for science literacy. New York: Oxford University Press.
Champagne, A., Klopfer, L. E., & Anderson, J.H. (1980). Factors influencing the learning of classical mechanics. American Journal of Physics, 48, 1074-1079.
Clement, J. (1982). Students' preconceptions in introductory mechanics. American Journal of Physics, 50, 66-71.
Dekkers, P. J. J. M., & Thijs, G. D. (1998). Making productive use of students’ initial conceptions in developing the concept of force. Science Education, 82, 31-51.
diSessa, A. A. (1983). Phenomenology and the evolution of intuition. In D. Gentner & A. L. Stevens (Eds.), Mental Models (pp. 15-33). Hillsdale, NJ: Lawrence Erlbaum
Associates.
Gilbert, J., & Watts, M. (1983). Misconceptions and alternative conceptions: Changing perspectives in science education. Studies in Science Education, 10, 61-98.
Gopnik, A., Meltzoff, A. N., & Kuhl, P. K. (1999). The scientist in the crib: Minds, brains, and how children learn. New York: William Morrow and Company, Inc.
Halloun, I. A., & Hestenes, D. (1985). Common sense concepts about motion. American Journal of Physics, 53, 1056-1065.
Ioannides, C., & Vosniadou, S. (2001). The changing meanings of force: From coherence to fragmentation. Cognitive Science Quarterly, 2(1), 5-62. Retrieved October 30, 2006,
from http://www.cs.phs.uoa.gr/el/staff/vosniadou/force.pdf
McCloskey, M. (1983). Naive theories of motion. In D. Gentner & A.L. Stevens (Eds.), Mental models (pp. 299-324). Hillsdale, NJ: Lawrence Erlbaum Associates.
Minstrell, J. (n.d.). Facets of students’ thinking. Retrieved October 27, 2006, from http://depts.washington.edu/huntlab/diagnoser/facetcode.html
Minstrell, J. (2004) Diagnoser. Found at www.diagnoser.com
National Research Council. (1996). National science education standards. Washington, DC: National Academy Press.
Reiner, M., Slotta, J. D., Chi, M. T. H., & Resnick, L. B. (2000). Naive physics reasoning: A commitment to substance-based conceptions. Cognition and Instruction, 18, 1-34.
Trumper, R., & Gorsky, P. (1996). A cross-college age study about physics students’ conceptions of force in pre-service training for high school teachers. Physics Education, 31,
227-235.
von Hofsten, C., Vishton, P., Spelke, E. S., Feng, Q., & Rosander, K. (1998). Predictive action in infancy: Tracking and reaching for moving objects.
Massachusetts Department of Elementary and Secondary Education
Force and Motion
9
Conservation and Transformation of Energy
November 15, 2010
Conservation and Transformation of Energy
Concept and Skill Progression for Conservation and Transformation of Energy
The progression begins by defining energy through the distinction of its types or forms, then goes into the nature of energy, and then into helping students to understand the
difference between potential and kinetic energy by focusing on explaining potential energy. After that, heat is introduced, followed by a section on distinguishing between energy
and energy resources.
NARRATIVE STORYLINE
Initial Ideas
Before instruction children are familiar with the term “energy” through everyday experiences. However, their definitions often contradict expected scientific meanings. Students
initially believe that energy is not conserved, that it “flows” from object to object, or that is the same thing as force. They believe that energy is associated primarily with motion and that
an object at rest has no energy or has used up all its energy.
Conceptual Stepping Stones
Upper Elementary school students can learn the concept of heat without having had a formal introduction to the concept of energy. They can observe, measure, and compare temperature
differences and changes that help them to understand, for example, that heating is the process through which two touching objects of different temperatures change their temperatures.
They can also experience light, motion, heat and wind, and identify instances where there is “more of” or “less of” each.
Middle school students can learn what energy is by learning about its different forms or types, and that it can be transformed from one type to another. They can differentiate between
the types of energy using their corresponding indicators. Students study energy in a qualitative rather than quantitative way, comparing more or less, or the loss or gain of energy of a
given type. Students can distinguish between energy and its sources, recognizing that different energy sources (such as solar, nuclear, and wind) in different situations have advantages
and disadvantages.
Culminating Scientific Ideas
High school students can understand and use the concept that energy can be transferred and transformed within a closed system is emphasized. They can also grasp that he gravitational
energy between two objects depends on the distance between the objects. Students can now calculate amounts of energy using various formulae for the different types.
Massachusetts Department of Elementary and Secondary Education
Conservation and Transformation of Energy
10
Conservation and Transformation of Energy
Lower Anchor
Reflective of student concepts
November 15, 2010
Conservation and Transformation of Energy
Upper Anchor
Reflective of science concepts
Reconceptualization
CONCEPT & SKILL DETAILS
Initial Ideas
Conceptual “Stepping Stones”
Culminating Scientific Ideas
Students who view the world in this way believe and can:
Students who fully understand this topic
believe and can:
Before instruction, students often believe and can:
Pre-instruction
Elementary School 1
Middle School
High school
What is Energy? 2
What is Energy?
What is Energy?
What is Energy?
Possible Misconceptions:
Students use the term energy in everyday language
with non-scientific purposes. It therefore has
meanings for students that contradict excepted
scientific meanings. For example, students say that
they “feel like they have little energy”3 or that
“turning off the lights saves energy.” 4
Students experience light, motion,
heat and wind, and identify instances
where there is “more of” or “less of”
each.
Distinguish between different types6 of
energy:
 Kinetic energy is associated with the speed
of an object.
 Thermal energy is associated with the
temperature of an object.
 Gravitational energy is associated with the
elevation of an object.
 Elastic energy is associated with the
deformation of an object.
 Light energy is associated with light
intensity.
 Sound energy is associated with sound
intensity.
 Electrical energy is associated with closed
circuits with power sources.
 Electrostatic energy of a system of objects
that contain electric charges is associated
with the distances among the objects.
 Chemical energy is associated with the
chemical configuration of substances. For
instance, the chemical energy of gasoline
and oxygen changes into thermal energy
when gasoline burns. 7
Understand that energy can be
transferred and transformed. Within
a closed system the total energy is
conserved.
Students seem to have at least two intuitive
metaphors for energy: as a “substance” and as
“activation.”5
Recognize that the gravitational
energy of a system of mutually
attracting objects is associated with
the distances among the objects.
Objects, even those that do not glow, emit
light energy. This light can be visible or
invisible.
Massachusetts Department of Elementary and Secondary Education
Conservation and Transformation of Energy
11
Conservation and Transformation of Energy
General Nature of Energy
November 15, 2010
General Nature of Energy
Possible Misconceptions:
Students may believe that energy has to do with
living and moving things only.
Students may believe that the ‘flow transfer’
model in which energy is thought of as a fluid: it is
assumed possible for energy to be ‘put in’, ‘given’,
‘conducted’ or ‘transported’ and energy is thought
to flow out of one thing into another.
Students tend to view energy as a reactive agent
rather than a causal one, lying dormant within
objects until something triggers it. It is assumed to
appear all of a sudden as a result of some
combination of ingredients.
Students tend to view energy as a by-product of a
situation, rather like a waste product. It is relatively
short-lived product that is generated, is active, and
then disappears or fades away.
Students may believe there is no distinction
between force and energy.
Student may believe that an object at rest has no
energy.
Conservation and Transformation of Energy
General Nature of Energy
General Nature of Energy
Understand that energy can be transformed
from one type to another. 9
Calculate energy using various
formulae.
Investigate how energy is transformed into
and from one type to another.
Recognize that work is a process
through which energy is transferred
through pushes and pulls exerted on
an object over a distance. For
mechanical interactions, that require
contact among objects; for electrical
and magnetic interactions, work is a
process through which energy is
transferred through pushes and pulls
exerted at a distance on electric
charges or magnetic objects.
Qualitatively measure energy and complete
basic quantitative measurements of energy.10
Understand that whenever some energy
seems to disappear from a place, some will
be found to appear in another. A decrease
(increase) of the total amount of energy in
one location is always accompanied by an
equal increase (decrease) of the total energy
in another.11
Possible Misconceptions:
Without deep grounding in forces, students
tend to conflate between forces and energy.
Problematic ideas include that the existence
of a force is always accompanied by an
energy transfer; and gravitational energy is
greater when an object is closer to the Earth
because the gravitational force is greater.
Students may believe that energy is truly lost in
many energy transformations. Things go until
energy is used up.
Students may be thinking about energy as
“accomplishment-oriented.” That is, energy is
used to do things, or make things.
Students are generally not sure when energy is
coming into a system, or going out, or appearing
after being stored within. They are most
comfortable with the idea that it is passed on from
one object to the next, more than the idea that
energy is stored within or comes in or goes out. 8
Massachusetts Department of Elementary and Secondary Education
Conservation and Transformation of Energy
12
Conservation and Transformation of Energy
November 15, 2010
Potential Energy
Conservation and Transformation of Energy
Potential Energy
Possible Misconceptions:
Students tend to associate energy primarily with
motion.
Students may believe that potential energy is a
thing that objects contain (like cereal stored in a
closet).
Potential Energy
Define potential energy as energy that is not
associated with motion.12
Define potential energy as the result
of the interaction between objects.
Recognize that potential energy can be
transformed into kinetic energies (energies
associated with motion).
Distinguish between potential
(gravitational, elastic, chemical, and
electric) and kinetic (kinetic and
thermal) types of energy.
Possible Misconception:
Students often believe that the only type of
potential energy is gravitational.
Heat
Heat
Possible Misconceptions:
For some students, heat is thought of as a property
of an object, such as the object’s thermal energy.
Understand that heating13 is the
process through which two touching
objects, one of which is colder than
the other, change their temperature,
i.e., their thermometer readings.
Students may conflate heat and temperature.
Students may take heat as body temperature and
see humans as the standard for measuring heat.
Students may believe that any temperature above
freezing represents heat and that cold is any
temperature below freezing.
Students may associate heat living objects, sources
of heat, the degree of hotness of objects, and the
effects of heat on objects.
In comparing the rate of heating, students may
explain it as the relative strength/weakness of the
heat in that given situation.
Student may believe that heat and cold are
different entities, not as part of the same
continuum. Cold is the opposite of heat.
Students may believe that the state of hotness or
coldness depends on the material from which the
Recognize that when two objects
touch, the colder object increases its
temperature and the warmer object
decreases its temperature.
Recognize that it is possible to
change the temperature of an object
without heating, e.g., when two
identical objects that have the same
temperature as each other are rubbed
together.
Heat
Heat
Understand that when an object’s thermal
energy decreases, some of this energy is
transformed into another type of energy or
transferred to the surroundings.15
Understand that heat is the amount
of energy gained or lost by an object
due to a temperature difference with
its surroundings.
Understand that this energy may be
transferred through conduction, convection,
or radiation.
Recognize that objects radiate
electromagnetic energy of all
frequencies.
Recognize that increased temperature means
greater average kinetic energy16 due to
increased random motion of atoms and
molecules.
Measure temperature differences and
changes (without mentioning
energy).14
Recognize that all objects in a room
have the same temperature, except
people, a hot stove, etc.
Describe ice melting, water boiling
Massachusetts Department of Elementary and Secondary Education
Conservation and Transformation of Energy
13
Conservation and Transformation of Energy
object is made (Wool is warm and warms things;
metal is cold, and cools things).
November 15, 2010
Conservation and Transformation of Energy
and temperature changes in water
during a change of state.
Students may think that heat can add weight to the
object being heated.
Energy vs. energy resources
Energy vs. energy resources
Possible Misconceptions:
Students may believe that energy is synonymous
with fuel and phrases like ‘energy crisis’ and
‘conserve energy’ means ‘fuel crisis’ and
‘conserve fuel’.
Distinguish between energy and energy
sources.
Students may believe that energy is a very general
kind of fuel.
Recognize that an energy resource is a
naturally occurring energy source.
Understand that energy sources typically
“store” energy in one of its potential forms.
Recognize that different energy resources
have different advantages and disadvantages,
primarily their renewability and the hazards
associated with their use.
Recognize that energy distribution is done
primarily through the electric power grid.
Recognize that any energy source (such as
nuclear, solar, biomass) can be used to either
heat water into steam that can drive a turbine
coupled to a generator, or to directly drive a
turbine (wind, water).
Recognize that solar cells can directly
transform solar energy into electrical energy.
Grades
Pre-instruction
Elementary School
Middle School
High school
Key Vocabulary
heat, light, motion, state,
temperature, wind
Massachusetts Department of Elementary and Secondary Education
chemical, closed circuit, composition,
conduction, convection, deformation, elastic,
electric charge, electrical, electrostatic,
elevation, emit, energy, gravitational,
intensity, nuclear, potential, power source,
radiation, sound, substance, thermal
closed system, electrical work,
electromagnetic, mechanical work,
transfer, transform
Conservation and Transformation of Energy
14
Conservation and Transformation of Energy
November 15, 2010
Conservation and Transformation of Energy
Authors and Reviewers
Dr. David Fortus, Weizmann Institute, Israel (contributor)
Dr. Stamatis Vokos, Seattle Pacific University, Washington (contributor)
Dr. Arthur Eisenkraft, University of Massachusetts, Boston, Massachusetts (reviewer)
References
None provided at this time.
Notes
Explicit instruction about energy in early elementary school needs to be done in an age-appropriate manner. Energy is an abstract concept that is often at odds with students’ everyday use of the
term. Early elementary school should focus on observation, organized recording of observations, and identifying patterns.
2
There is no accepted definition of energy. Any attempt to present an operational definition to students will be incorrect and misleading. Students should develop an understanding of energy similar to
their understanding of time – they cannot define it or explain what it is, but they know how and when to use it. Energy is a very abstract concept, whose operational definition is very difficult even
for professional scientists of different domains. For instance, chemical energy may mean different things to chemists and physicists. In instruction, energy may be therefore rendered
meaningless—especially in lower grades. It may be easily confused with other related terms, such as interaction, force, friction, heating, etc. It may be associated with unhelpful ideas of
“activation,” as in the oft-used statement “Energy is the ability to do work.” Yet, energy instruction can lead to powerful learning when grounded in evidence of changes in the object(s) in
question.
1
3
4
The students often are seeing themselves as an energy source.
The students typically are using “saved” to mean transferred into the system or not.
5
The substance metaphor is more useful in that it automatically encourages students to think of energy as being conserved, whereas the activation metaphor too easily leads to energy being created
and destroyed as something gets more or less “excited.” Some scholars have serious concerns about the substance metaphor, perhaps because it might lead to the incorrect idea that energy takes
up physical space, which is especially problematic in thinking about interaction energy. This may be a concern, however, as the benefits may greatly outweigh the risks. (Sam McKinney, private
communication)
6
The term “energy type” is preferable to “energy form”. “Form” has an association with “shape” and may lead to misconceptions. When introducing energy transformations, it is preferable to use the
term “energy conversions”.
7
Chemical energy is not stored in chemical bonds, as is often claimed. “Stored” implies that the energy in a bond is greater before the bond is broken than after. The opposite is true for attractive
bonds. In exothermic reactions, energy is released during the making of new bonds rather than the breaking of the bonds of the reagents.
8
In this sense, energy seems to be a linear propagation of causal power until it achieves its goal and is extinguished, maybe like fire in a line of gunpowder. (Hunter Close, private communication)
9 “Transformation” sounds very similar to “transfer” and this confuses students. In addition, the term “conversion” allows to build off an analogy with currency – when money is changed from one currency to another, the value doesn’t change (other than the bank’s service charge, which is like the
energy lost to the surroundings as heat), just the way in which the money appears. The term “transformation” should only be introduced after the idea of transfer has been learned.
10
It is inappropriate before middle school to calculate amounts of energy using the various formulae for the different energy types. Energy measurement should remain qualitative to semiquantitative: more or less energy of a given type. For example, as a ball falls, one type of energy (gravitational energy) decreases and another (kinetic energy) increases.
11
Without recognizing it, students will not be able to accept that “energy cannot be created or destroyed. The idea that “most processes involve the transfer of energy from one system to another” is central to acceptance that “energy cannot be
created or destroyed”. Energy transfer should be shown to be the result of a series of energy transformation. For example, when a moving ball strikes a stationary one, kinetic energy is transformed into elastic energy which is then transformed back into kinetic energy.
Potential energy is an especially problematic concept. That is the reason that the word “potential” does not appear in the target energy ideas outlined above. The labeling of the corresponding form
(gravitational, elastic, electrostatic) is more important. Potential energy for many learners of all ages involves the colloquial use of the term, rather than its association with a mathematical scalar
function, called potential. Colloquially, we use the term to mean an inherent tendency. So, an un-stretched rubbed band has non-zero potential energy because it has the potential to be stretched.
Similarly, an un-magnetized nail has potential magnetic energy because it bears within it the possibility of becoming magnetized. A book placed on the center of a table has smaller potential
energy than when it is placed closer to the edge, because closer to the edge, it has a greater chance of falling. So, for some learners, potential energy is energy potential or the potential to release
that energy (as in the book close to the edge of the table) or the potential to get into an activated state (such as the nail).
13
At this stage it is preferable not to use the term “heat” as a noun at all, just as a verb.
14
Suggested activities include:
12
Massachusetts Department of Elementary and Secondary Education
Conservation and Transformation of Energy
15
Conservation and Transformation of Energy
November 15, 2010
Conservation and Transformation of Energy
A. Cold or hot water slowly getting warmer or colder until it is at room temperature
B. Objects of different temperature put in physical contact with each other
C. Repeat (A) when water is in containers of different thermal conductivity
D. The difference between the sensation of hot and cold and the measurement of temperature
E. Different amounts of water being heated by an identical flame
F. Watching the currents generated as water is being heated in (D)
G. Using sunlight to heat identical objects with different colors (white, black, and silver)
15
All discussion of heat transfer should be done in terms of changes to an object’s thermal energy. Students should be given multiple opportunities to see that other types of energy are transformed
into thermal energy and transferred to the surroundings in all macroscopic phenomena.
16
Students likely will need some evidence for this view of energy at the molecular level.
Massachusetts Department of Elementary and Secondary Education
Conservation and Transformation of Energy
16
Properties & Transformations of Matter
November 15, 2010
Properties & Transformations of Matter
Concept and Skill Progression for Properties and Transformations of Matter
This progression is organized around four core ideas: all material is matter made up of particles held together by bonds; all materials, including gasses, have weight that does not
change during phase change and other physical transformations; the volume of an object does not change even if the particles are physically rearranged; density is a property of
materials that is dependent on the amount of material (mass) per unit volume.
NARRATIVE STORYLINE
Initial Ideas
Before instruction children are able to name different kinds of materials and describe some readily observable properties such as the softness/hardness and shininess of materials. Some
young children can even see that when a solid object is broken into pieces, the identity of the material of the pieces are the same as the identity of material of the whole object, as long as
surface properties are maintained. Young children can also differentiate between solids and liquids and between physical entities and non-physical entities such as feelings or ideas.
However, young children tend to conflate material with shape/function when sorting objects. They often believe weight can be measured by hefting and that weight is a property of
objects. When it comes to an object’s size, young children sometimes associate the word “big” solely with length or height.
Conceptual Stepping Stones
Early elementary students understand that an object can be made of different materials and that a given material has specific properties. They can classify objects according to function or
shape and can differentiate between an object’s characteristic versus the characteristics of its material. Students can associate weight with material and they know that the weight of an
object depends on what the object is made of. They know that when a chunk of material is cut into pieces, no matter how small, each piece still represents that material. Students can
measure and differentiate between length and area and occupied three-dimensional space and know that the amount of an object’s material is conserved even if the object shape is
changed. Students can justify why two objects made of the same material but of different sizes have different hefts, and two objects of the same size made of different materials can have
similar hefts. Students can differentiate between a solid and a liquid and some macroscopic properties of these two states. Students understand on a basic level the elemental makeup of
macroscopic objects and can also learn to model the structure of materials.
Late elementary students expand their understanding of the states of matter beyond liquids and solids to include gases. They understand that gases have weight, which does not change
during phase changes or other physical transformation. They understand matter at the particulate level and that a material is composed of particles held together by bonds. Students know
that as heat is added to a material, its particles move faster and farther apart. They know that at the boiling point, they move fast enough and far enough away from each other that they
do not have bonds between them any more. Students can differentiate between volume and weight as well as between weight and “heaviness-for-size,” the precursor to the concept of
density (which should be introduced in middle school). They recognize that objects made of some materials (e.g., steel) are heavier-for-their-size than objects made of other materials
(e.g., wood). They can associate heaviness-for-size to the particulate model understanding that some objects are heavier for their size because they are made of heavier particles and/or
because their particles are closer together.
Culminating Scientific Ideas
Middle school (not yet included)
Massachusetts Department of Elementary and Secondary Education
Properties & Transformations of Matter 17
Properties & Transformations of Matter
November 15, 2010
Lower Anchor
Reflective of student concepts
Properties & Transformations of Matter
Upper Anchor
Reflective of science concepts
Reconceptualization
CONCEPT & SKILL DETAILS
Initial Ideas
Conceptual Stepping Stones
Culminating Scientific Ideas
Students who view the world in this way believe and can:
Students who fully understand this topic
believe and can:
Before instruction, students often believe and can:
Pre-instruction
Material
Young children often know aspects of what
constitutes “material:”
a) They know different kinds of liquids
(milk, water, orange juice, perhaps oil)
and their names.
b) They are sensitive to properties such as
softness/hardness, shininess, squishiness
breakability, and smell.1
c) They may know “wood,” “plastic,” or
“metal.”2
Some four-year-olds preserve the material
identity of some solid materials when a chunk
of material X is cut into smaller chunks as
long as surface properties (e.g., hardness) are
maintained.
Possible Misconceptions:
Young children have beliefs about some
materials but they do not have a concept of
material (kind), i.e., they do not have a
meaning for the word “material,” or a cluster
of beliefs that apply to all materials.
Young children privilege the description of an
object in terms of the kind of object it is (e.g.,
a spoon) and treat the material, when they are
aware of it at all, as a perceptual property of
the object (in “This spoon is large and metal,”
the meaning of “metal” is akin to the meaning
of “metallic” and means, e.g., “shiny, cold to
Early Elementary (grades K-3)
3
Material
In this grade range, students develop a
concept of material kind, i.e., they learn
that objects are made of different
materials and what that material have
specific kinds of properties. This
includes:
o Differentiating an object (which has a
specific shape and/or function) and the
material it is made of.4
o Properties such as hardness/softness,
smell and taste, brittleness, behavior
when heated (gets warm quickly,
melts easily), are now associated with
materials, not with objects.
o Differentiating “made of” from “made
from;” “made of material X” means
“constituted of little pieces of material
X all the way through.”
Students can classify objects according to
kind of objects, function and/or shape, vs.
according to the material they are made
of.
Students differentiate properties that
characterize objects (e.g., size) from
properties that characterize materials
(e.g., hardness). They can reason “The
reason this flower pot gets darker when it
is wet, is that it is made of clay, not that it
is a flower pot. They start developing a
Massachusetts Department of Elementary and Secondary Education
Late elementary (grades 4-5)
Material
Students know:
o All solid and liquid objects are made of
one or more specific materials.5
o All materials are forms of matter (see
Matter below)
o know that materials differ in hardness,
heaviness-for-size, melting points and
boiling points, smell and taste, how fast
they get hot and cold, how soluble they
are in water (perhaps also how well they
conduct electricity). These properties
characterize materials irrespective of
amount.6 In particular, if a piece of
material X is heavier than an equal size
piece of material Y, any piece of material
X, no matter how small, will always be
heavier than a same size piece of material
Y.
o How to differentiate material specific
properties like those mentioned above
from “accidental” properties, such as color
(needs qualification, as some materials
have characteristic colors and texture). To
know whether two materials are really the
same, students can check their inherent
properties (see paragraph above).
o “Made of material X” means constituted
of X particles (Particulate Model, see
Matter Structure below).7
o Material identity is preserved through
Middle School
(not yet included in Progression)
Properties & Transformations of Matter 18
Properties & Transformations of Matter
the touch, whitish”). Young children often
cannot focus on the “stuff” independently of
the object. This is in part because the object
level of description has been central from
infancy: objects are permanent, one can act on
them, they act on each other, etc. Their
perceptual properties are important (bounces,
is soft, is sweet to eat) but they are associated
with objects, not with a separate concept the
material the object is made of. So they may be
surprised that a wood ball does not bounce
because they have encoded their experiences
with balls as “balls bounce” not “rubber things
bounce.” For the same reason, a piece of wood
is only an object, not a sample of the material
wood.
For many children, “made of” means
“constituted of parts” (we are made of blood,
bones and skin) or “made from” (milk is made
from cows).
November 15, 2010
sense of properties that are inherent in
materials (e.g., hardness) from those that
tend to be more accidental (color).
Students learn many materials’ names
(solids and liquids) and have some sense
of a hierarchy in material names (e.g.,
gold and aluminum are kinds of metals;
oak and maple are kinds of wood).
Properties & Transformations of Matter
physical transformations: cutting,
grinding, dissolving, melting and freezing,
evaporation, boiling, condensation.8
o The difference between inherent
properties of materials (hardness, melting
point) and “accidental” ones introduced at
the end of the early elementary grade
range can be consolidated (see Matter
Structure below).9
Students can associate weight with
material. (see Density below)
Students know that when a chunk of
material X is cut into pieces, no matter
how small, each piece is still material X.
They can use a mental model of a chunk
of solid material X composed of tiny
pieces of X; when it is ground, the pieces
keep their identity as pieces of X.
Young children often conflate material with
shape/function when sorting out objects by
these features. They also can conflate
attributable properties that depend on material
(e.g., hardness, gets darker when wet, attracts
a magnet) to objects (i.e., the reason this
flower pot gets darker when wet is that it is a
flower pot, not that is made of clay).
Material identity is typically not preserved
when a chunk of (solid) material is ground or
melted, because its perceptual properties
change.
Young children often believe that when
liquids evaporate or boil, they cease to exist
(because they cannot be perceived any more).
Massachusetts Department of Elementary and Secondary Education
Properties & Transformations of Matter 19
Properties & Transformations of Matter
Weight
Possible Misconceptions:
Students often believe weight is “measured”
by hefting. Heft is at the core of the concept of
weight—it is a given. The only way to know
for sure how heavy something is to heft it.
Students often believe weight is not a property
of matter, it is a property of (some) objects.
As with material (see above), the object level
of description is the most salient; in the
absence of a concept of “kind of stuff,” it is
objects that have substantiality and therefore
weight is associated with objects, not the
material.
Some young children associate the heft of
objects with other perceptual properties (e.g.,
if a shiny and red sphere is heavier than a dull
and green cube, they predict that a shiny and
red cube will be heavier than a dull and green
sphere).
Students often believe not all objects have
weight. Some are “light” in the sense of not
having heft at all (and therefore no weight) or
very little heft (e.g., a feather; a grain of rice).
Some are light in the sense that they rise (e.g.,
balloons). Some objects don’t weigh anything
irrespective of size (e.g., Styrofoam pieces);
some objects have weight only if they are
large enough (e.g., a ball of clay). Little pieces
of any material don’t weigh anything.
November 15, 2010
Weight10
Students develop an objective, extensive
concept of weight, which is a property of
matter. (Matter in this grade range only
includes solids and liquids).11 This
includes:
o Weight is measured with a scale and is
therefore objective.
o Weight is differentiated from heft.12
o Weight is extensive: if object A
weighs X units and object B weighs Y
units, the two objects together weigh
X + Y units.
o Any piece of solid material, however
small, visible or not, has weight.13
o Weight is a property of amount of
material, not of objects (i.e., if the
shape of an object changes, but no
matter is added or removed, weight
stays the same).14
o The weight of objects depends on
what the objects are made of.15
Properties & Transformations of Matter
Weight
Students understand that gases have weight
(and are therefore material, see Matter
below).
(not yet included in Progression)
Students know weight does not change
during phase change and other physical
transformations.
Students view weight as a force (link with
Force and Motion). It is proportional to
amount of material (within one material).
Students know that data acquired via our
unaided senses are not as precise as
measurements, and can be incompatible
with them.
In some contexts weight is relative to the
“hefter:” the same object can be heavy for the
child and light for an adult, or have not weight
for the child but have weight for an ant.
Students often believe weight changes when
shape changes (because object identity
changes). For example, when a clay ball is
Massachusetts Department of Elementary and Secondary Education
Properties & Transformations of Matter 20
Properties & Transformations of Matter
November 15, 2010
Properties & Transformations of Matter
rolled into a sausage, children say its weight
changes.
Students often believe that if a heavy object
(as assessed by hefting) is placed in one pan
of a balance scale, and a light object in the
other, children predict the heavier one makes
the pan go down. If the scale does not behave
according to hefted weights, hefted weight is
“right” and some other explanation for the
balance scale behavior is sought (e.g., size as
well as weight must be relevant to the scale’s
behavior).
To young children, the senses “tell the truth.”
This is closely related to the core of their
concepts (materials, solids and liquids, weight,
size) being perceptually based.
Size (length, area, volume)
Young children have precursors to
geometrical concepts of length, area, and
volume, ideas embedded in perception and
action, and not yet abstract. They know that
some objects occupy more space on the
ground, table, etc. than others. And they have
a concept of bigness, a precursor of volume-big objects are hard to carry and move and do
not fit in small spaces; large objects do not go
through small holes. They also know from
infancy that two objects cannot occupy the
same space at the same time.
Size (length, area, volume)17
Students can differentiate length, area,
and occupied 3-D space (precursor to a
full-fledge concept of volume). Students
understand:
o The measurement of length and area
conceptually (rather than as
procedures).
o How to measure length and area .
o The volume of a solid does not change
if it changes shape (modeling clay,
e.g.) or is cut into pieces.
Possible Misconceptions:
Students may believe “length” can be
associated with “points of departure and
arrival” so that they do not (clearly)
understand that different paths connecting two
points have different lengths.
“Big” sometimes mean long, sometimes tall
Massachusetts Department of Elementary and Secondary Education
Size (length, area, volume)
Volume
Students know that water displacement
depends on size, not weight (see Weight
above), and can use water displacement as an
indicator of how much space an object
occupies.18
(not yet included in Progression)
Students learn volume conservation. An
object can be composed of little pieces that
get rearranged, but do not change shape,
appear or disappear when the object is reshaped.19
Students can differentiation volume and
weight. Different objects made of different
materials can have the same volume but
different weights.20
Students develop a sense of “size of a
bounded region of space” as well as using
mathematical formulas to compute the area
and volume of regular shapes.
Properties & Transformations of Matter 21
Properties & Transformations of Matter
for young children; those dimensions need to
be differentiated from each other and from the
2D and 3D meaning of “big.” Finally, young
children believe that solid objects displace
water according to their weight as well as their
size.16
Density
Some young children have a very distant
precursor of density: objects made of some
materials are light (e.g., Styrofoam); others
are heavy (e.g., brass).
Matter (macroscopic)
Young children have a sense of “materiality”
or “substantiality:” (solid) objects and liquids
can be touched and seen; (solid) objects can
also be held (depending on size). Solids and
liquids are different from other physical
entities (e.g., light, wind, electricity) and from
non physical entities (e.g., ideas, emotions);
they are different from each other.
As noted in the Material section above,
students typically know that liquids and solids
behave very differently and only have one
thing in common (being touchable and
November 15, 2010
Properties & Transformations of Matter
Density21
Density22
Students have two empirical
Students are developing and achieving the
generalizations which are yet unrelated-concept of heavy-of-size (not yet a formal
“Bigger objects are [usually] heavier than notion of density). Students:
smaller objects;” “Objects made of
o Recognize that objects made of some
material X are [usually] heavier than
materials (e.g., steel) are heavier-for-theirobjects made of material Y.” With these,
size than objects made of other materials
students can justify why two objects
(e.g., wood).
made of the same material but of different o Know that heaviness-for-size is true of
sizes have different hefts, and two objects
objects of any size, including tiny ones.23
of the same size made of different
o Differentiate heaviness-for-size from
materials can have similar hefts.
weight.
o Can account for heaviness-of-size in terms
of the particulate model (see Matter
below): objects made of some materials
are heavier for their size than objects
made of other materials because they are
made of heavier particles (or/and because
their particles are closer together). In
contrast, the weight of an object depends
on the number of particles, i.e., on its
volume.)24
26
Mass (amount)
Mass (amount of material)27
Students know:
Quantification of amount is still within a
o How to quantify the amount of
given material, but students in the 5th grade
specific materials (e.g., amount of
are introduced to the notion of amount of
clay, amount of water). “This object
matter (mass):
has more clay than that object; this
o Explicit differentiation of volume and
beaker has more water than that
amount of material. Students learn that
beaker” make sense in terms of “units”
the same amount of a given material
of clay, water, etc. This quantification
(e.g., iron or alcohol) occupies more or
is based on a mental model, the
less space, i.e., has a greater or lesser
compositional model, in which an
volume) depending on temperature.28
object is broken into a set of equal
(Link with Energy) The particulate
pieces.
model (see Matter below) can be used to
o The amount of material is conserved
Massachusetts Department of Elementary and Secondary Education
(not yet included in Progression)
(not yet included in Progression)
Properties & Transformations of Matter 22
Properties & Transformations of Matter
seeable).25
Possible Misconceptions:
Children often believe that materials disappear
when they dissolve (e.g., sugar in water) and
can no longer be seen (taste might still be
there).
Gases and smoke are not materials (because
they cannot be seen or touched).
When liquids boil or evaporate, they cease to
exist because they cannot be perceived any
more.
Mass (amount of stuff)
Young children have a concept of “bigness,”
which is a property of objects, and is judged
perceptually. When asked “which has more
[clay, juice],” children assess which is bigger;
they do so by focusing on one aspect of
bigness (height, area covered). They may also
take into account whether anything was
added—part of the meaning of “more” is
sensori-motor: “more” means “something
added. It often correlates with bigness--If you
pour more juice into the glass, the level rises.
But “more” does not refer to quantity of
material.
November 15, 2010
(on principled grounds). They know
that, if the shape of an object changes
(e.g., when a clay ball is flattened into
a pancake) it is not the same object but
it is the same amount of clay. Their
compositional model allows them to
envision the clay before and after
transformation as made of the same
number of small clay “units” that are
spatially re-arranged when the object
shape changes but continue to exist;
their number remains the same. It is
also applied when an object is cut into
pieces.
o The amount of material is related to
weight and understand that weight
does not change when shape changes
because amount of material is
conserved.
Matter (macroscopic)
Students can differentiate solids and
liquids. They know:
o Any piece of solid material, however
small has weight and takes up space.
So does every little drop of liquid.
o Solids keep their shape, liquids take
the shape of their containers.
o There are different kinds of liquid
(materials)—milk, OJ, water, oil,
gasoline, etc., in the same way there
are different kinds of solid materials.
o Some materials can exist in the two
states.29
Possible Misconceptions:
When a ball of clay is flattened into a
pancake, children often say it now has more
(or less) clay. This is because they lack a
concept “amount of clay [stuff]”; they focus
instead, e.g., on area covered on the table by
the clay; i.e., they focus on “something more
related to the clay.” Some children evince
Massachusetts Department of Elementary and Secondary Education
Properties & Transformations of Matter
account for thermal dilation and
contraction. Volume also becomes more
abstract (see Size above) and more
purely geometrical. As a result, amount
of material becomes less tightly linked to
volume and more to the “stuff”
occupying space.
o Two objects made of different materials
that have the same weight have
something important in common—they
have the same weight because they have
the same amount of “stuff”—the earth
pulls equally strongly on both objects.
(Link with gravitational force) The
reason they have different volumes is
that “stuff” is more packed in the smaller
one or/and it is made of larger particles.
(See Matter, Structure below)
Matter (macroscopic)
Students know that:
o Matter occupies space and has weight.
Any little piece of material has weight and
occupies space.
o Solids, liquids and gases are forms of
matter.
o Some materials exist in all three phases on
earth (water); some don’t because they
change phase at extreme temperatures or
extreme pressure. Some burn rather than
melt.
o Material identity and amount of material
are conserved during phase change.
Weight stays the same during physical
transformations.
(not yet included in Progression)
Properties & Transformations of Matter 23
Properties & Transformations of Matter
November 15, 2010
Properties & Transformations of Matter
conflict—it covers more area but I did not add
any clay…For other children the two
meanings of “more” don’t have to be
consistent.
When a ball of clay is broken into several
pieces, some children think the ball has more
clay because it is bigger; others say that the
pieces have more clay because there are more
of them. Lacking a concept of amount of clay
[stuff], they answer in terms of bigness or of
number.
Matter, Structure
Matter, Structure
Students learn to model the structure of
materials. They understand that
macroscopic objects that are made of
“constituting blocks” held by
“connecting” elements. For example, one
can create a sculpture made of Styrofoam
balls connected by wires. The strength of
the whole depends on the strength of the
connecting elements. They can then look
at materials that have a visible structure
(e.g., knitted fabric) and represent what it
is made of and what holds it together.30
Massachusetts Department of Elementary and Secondary Education
Matter, Structure31
Students hold a particulate model that they
use to understand:
o Material X is composed of particles of X
held together by bonds.32
o Particles of different materials are
different.33 They differ in weight and the
distance between them can be different for
different materials.
o Bonds are forces similar to the force
exerted between two magnets.
o There is nothing between particles.
o Particles move differently in the three
states of matter: they vibrate around a
fixed point in solids, they move past each
other in liquids, bonding with different
particles as they go; they move freely and
across large distances in gases. They are
much closer to each other in solids and
liquids than in gases.34 For a given
material, the average distance between
particles is almost the same in the solid
and liquid state (the difference is greater
for water than most other materials).
o When heat is added to a solid, its particles
move faster and a bit further away from
each other. At the melting point, they
change motion. At the boiling point, they
move fast enough and far enough away
from each other that they do not have
(not yet included in Progression)
Properties & Transformations of Matter 24
Properties & Transformations of Matter
November 15, 2010
Properties & Transformations of Matter
bonds between them any more.
Grades
Pre-instruction
Early Elementary (grades K-3)
Late elementary (grades 4-5)
Middle School
Key Vocabulary
Material, object, property, shape,
function, classify, solid, liquid, weight,
scale, length, area, space, measurement,
volume, conserve, structure
Matter, melting point, boiling point, conduct,
particle, physical transformation, gas, phase
change, force, proportional, displacement,
density, temperature, pressure, bond, vibrate
Notes
(1) Well chosen learning experiences can lead students to associate those properties with materials; e.g., knowledge could evolve from “balls bounce” to “rubber balls bounce but
wooden balls don’t” to “all rubber objects bounce” to “rubber is a bouncy kind of material.” And similarly “glass vases and drinking glasses break” to “things made of glass
break” to “glass is breakable.”
(2) Well chosen learning experiences may change the status of those words—from adjectives characterizing objects to nouns labeling the kind of stuff objects are made of.
(3) Relevant learning experiences:
o Classify objects by object kind vs. material kind (all the spoons together; all the plastic things together).
o Discover what different objects made of the same material have in common.
o Discover material identity conservation in simple contexts: establish that, if object A made of material X is cut into pieces, the pieces don’t constitute object A anymore,
but they are still made of material X.
o Expand vocabulary with names of materials.
o Foreground hardness, smell and taste, “hard to melt” and “gets warm easily when put in hot water” over color and shininess as distinctive properties of materials.
o Build a sense of “made of.” Develop a mental model of a chunk of material X as made of little pieces of X.
o Discuss why two equal size pieces of different materials have different weights. Students might propose that the lighter one is hollow, or that the heavier one contains
little heavy pieces. Cut chunks of materials to show students the chunks are made of the same material all the way through. When students propose that matter is more
“packed” in the heavier material, reinforce this idea. This idea will be revisited in the next grade band.
(4) Of course, function depends on both material and shape (a spoon made of wool is not particularly useful).
(5) “Object” has a very general meaning here—any bounded quantity of matter. Additionally, no distinction is made yet among element, substance, compound or mixture.
(6) Students in the later grade should be told that one needs a few hundred of particles for this to be true.
(7) No distinction is made between atoms and molecules in this grade range. Students may be told “Some particles are atoms, other are molecules.”
(8) Grinding, dissolving, melting and freezing can be presented in Grade 4; evaporation, boiling, condensation can be presented in Grade 5.
(9) This will be important in the next grade band, when students learn chemistry.
(10) Note: The importance of meaningful measurement in the development of scientific concepts cannot be overstated. This implies foregrounding precursors to the concepts (heft,
occupied space) and making them more scientific by quantifying them.
Relevant learning experiences
o The goal of these experiences is to foster the belief that weight a property of amount of material, and therefore an extensive property of objects, and the belief using a
scale rather than hefting is the proper way to measure weight. The two beliefs develop in inter-related ways. Moreover, developing a concept of weight consistent with the
scientific concept is closely linked with developing a concept of material (see Material section above).
o Observe that two same size objects made of different materials have different weight; and that is not because one is hollow, or the other one has heavy things added to it
inside. This learning experience begins to relate weight to “[kind of] stuff.”
o Array objects of different size and materials by weigh. Observe that, for a given material, weight increases with size. But that does not hold across materials. Objects
made of some materials are heavier than objects made other materials, although they are the same size or even smaller
Massachusetts Department of Elementary and Secondary Education
Properties & Transformations of Matter 25
Properties & Transformations of Matter
November 15, 2010
Properties & Transformations of Matter
o
o
Learn that a scale can help resolve uncertainties about hefted weight; it is more discriminate than hefting. Build trust in scale
Measure the weight of objects with non standard units (e.g., paper clips). Plot weights on a weight line. Discover that unit size matters (link with Epistemology, see
below). Children learn “The weight of the object is the same as the weight of N paper clips; N paper clips push on the scale pan as much as N paper clips. Then move to
standard units. By starting with non standard units, students do not simply learn using a scale as a routine; the process of using a scale is meaningful and helps them
reconceptualize weight.
o Use the weight line to discover the additivity of weight and that, if one keeps dividing a chunk of clay in two, the pieces will always weigh something, no matter how
small they are.
o Discover that water displacement depends on size, not weight or size and weight.
o Discover that weight does not change when shape changes (modeling clay) and when a chunk of material is cut into pieces. Activities are similar to those used for Amount
conservation (see below).
(11) Believing that any piece of matter has weight, although true only in a gravitational field, is extremely important for students to develop a more scientific understanding of
matter at both the macroscopic and nanoscopic levels (see the next grade bands). It will be revised later as “weight is a force exerted between masses” later on, when students
have a more developed understanding of mechanics.
(12) Heft becomes peripheral to the concept of weight. Hefted weight needs explaining—why is it unreliable? (instead of taking it for granted as in the Lower Anchor)
(13) This is crucial to learning the atomic-molecular model later on. Many students believe that atoms have no weight because they are very, very small. This makes the model very
problematic.
(14) This knowledge can be achieved via a compositional model—mentally viewing an object as made of little pieces of material that each have weight. What matters is how many
pieces there are, not how they are spatially arranged. Relating weight to amount of material is a precursor to the principle that weight is proportional to mass, to be learned in
middle school. Believing that weight is a property of matter is also crucial for understanding that amount of material is conserved during phase change and other physical (and
later chemical) transformations in later grades. Students who know weight is proportional to amount of material can verify that weight does not change during a physical
transformation and then infer that amount of material(s) has not change. In the same way, students can use empirical evidence that gases are have weight to infer that they are
material.
(15) This is a precursor to heavy for size and then density.
(16) Thus, children cannot start developing a scientific sense of 3D occupied space until they have constructed an objective concept of weight.
(17) Relevant learning experiences.
o Length. As with weight, understanding good measurement and developing a concept of length are two faces of the same coin. One should start with non standard units
(e.g., paper clips) before moving on to standard units and rulers.. “It takes 7 paper clips to cover this ribbon” leads to “This is a 7 paper clip long ribbon” and then to “The
length of this ribbon is 7 paper clips” or “7 is the length of the ribbon in paper clips.” After learning it is important that the paper clips be set end to end when measuring
the ribbon, standard units can be introduced— one inch wood sticks. Students can then place a ruler under the array of one inch sticks. The ruler’s divisions fit the one
inch sticks put end to end. The number one reads on the ruler is the number of one inch sticks.” Zero” on the ruler corresponds to the place where there is no stick to its
left—zero means “no inch [stick].” This series of activities give meaning to length measurement and foster the development of a mathematical concept of length.
o Area. The same approach should be used for area.
o Volume. Students can start reconceptualizing “bigness” into to occupied 3D space by placing objects of different sizes in boxes filled with sand. This can start
qualitatively (bigger objects displace more sand). Students can then measure how much sand spills out in each case (e.g., by filling and counting small cups). They will
realize that “This object takes as much space as this much sand.” Their initial concept of bigness gets reconceptualized into a quantifiable entity—the size of 3D space
occupied by an object.
Note. Good sources for information on measurement are Lehrer & Schauble and Sarama & Clemens.
(18) CC cubes can then be introduced. Students can first capture their observations as “N cc cubes take up as much space (displace as much sand/water) as Object X” and then
move to “The 3D space occupied by object X is N CC cubes.”
(19) Start with objects made of units that can be pulled apart and rearranged. Then move to clay. Develop the idea that a clay object can be envisioned as composed of little pieces
of clay that get rearranged, but do not change shape, appear or disappear when the object is re-shaped.
(20) Build sense of negative space and relate positive and negative space: if Object A displaces N ccs of water and fits into a certain size box, N ccs of water will fill the box. N
cc’s is both the volume of the object and the volume of the (empty) space inside the box.
Massachusetts Department of Elementary and Secondary Education
Properties & Transformations of Matter 26
Properties & Transformations of Matter
November 15, 2010
Properties & Transformations of Matter
(21) In this grade range, students do not have nor will develop a concept of density. But what they learn about weight, material, and volume contributes to developing a precursor to
density—“heaviness-for-size.” The relations between weight, object size, and the material an object is made of are not yet integrated into a concept of density. Relevant
learning experience: Arraying objects of different sizes and made of the same material by increasing weight—weight increases with size. Arraying objects of the same size
made of different materials—weight depends on material. Arraying objects of different sizes and made of different materials (see Weight above). Implicitly teach both size and
material matter. Students can verify that all objects made of the same material are arrayed by increasing size but that is not true across materials. Students are made aware that
“material matters;” some may come up with the concept of “heavy for size”—objects made of some materials are heavier for their size than objects made of other materials.
(22) Relevant learning experiences: Start with two equal size objects made of different materials, X and Y. One is twice as heavy as the other. Cut both in half. The weights of the
halves are half the weights of the original pieces but the half piece X is still twice as heavy as the half of piece Y. This is true as one keeps cutting. The activity can be summed
up as “Objects made of X are twice as heavy-for-their-size as objects made of Y.
(23) This is very counterintuitive because slivers of materials have no heft
(24) Students should master this knowledge before they learn about density mathematically.
(25) This difference is emphasized by the language--the names of solid objects refer to their shape and/or function whereas the name of liquids refer to the stuff and its properties
(milk); one asks for a spoon but for a glass of milk; etc. What solids and liquids have in common does not support many inferences or predications. Young children do expect
to see something they touch (with eyes closed or in the dark) and similarly expect to touch what they can see. Smoke and shadows are fascinating (and mysterious) to them
because they can be seen but not touched.
(26) Relevant learning experiences
o Conservation of amount. Start with Lego towers. Change their shape. “Is it still the same amount of plastic?” How could we know for sure? Count the Lego bricks before
and after transformation. Check with a scale. Note. This is typically a Kindergarten activity. Kindergartners’ understanding of weight is not sophisticated (see Lower
Anchor above) but seeing that two Lego constructions balance on the scale supports the belief that they are made of the same amount of plastic.
o Move to rice poured into different shape containers. Amount of rice is measured by pouring it into small identical cups. Amount does not change even though the level of
rice in the different shape containers is different. Then move to water poured into different shape containers.
o Also use clay. Cut the clay into small “bricks” to evoke the Lego experiments. Then invite students to imagine “very small bricks” “grains of clay” in the clay ball. They
get re-arranged when the clay ball is flattened into a pancake, but their number stays the same. (Develop the compositional model).
(27) Relevant learning experiences
o Explore thermal dilation of solids and liquids. In the later grade of this grade band, use the particulate model to explain thermal dilation.
o Discuss why two objects made of different materials can have the same weight and conversely why two same volume objects made of different materials can have
different weights. Elicit students’ ideas; ask them to draw models to represent their ideas.
Note. These activities are probably most useful prior to the introduction of the Particulate Model. They elicit students’ own ideas.
(28) A critical set of learning experiences revolve around thermal expansion.
(29) Students in this grade range are introduced to this idea only informally.
(30) This is a good vehicle for learning about modeling—they draw in order to communicate how they think about the material. They can move on to materials whose structure is
not visible and by analogy, imagine what the units and the connecting elements might be. This prepares students both in terms of content (the discontinuous nature of matter,
see middle school) and epistemologically.
(31) Relevant learning experiences
o Explain how one can smell objects at a distance
o Note. This is powerful empirical support for the Particulate model.
o Students use the particulate model to explain the conservation of material identity across physical transformations. They also can explain differences in density, hardness,
melting and boiling points between different materials. They can now understand the difference between “accidental” and inherent properties of materials: two materials
can look the same but, if they are made of different particles, they are different materials.
o Get a sense of why matter looks continuous—view clouds of dots from a greater distance.
o Get a sense of why air is not visible, although it is material. Show students a sheet of white paper on which 10 very small and faint dots have been place randomly. The
dots will not be visible from a distance. Then present the same 10 dots next to each other…
Massachusetts Department of Elementary and Secondary Education
Properties & Transformations of Matter 27
Properties & Transformations of Matter
November 15, 2010
Properties & Transformations of Matter
(32) Some might think that introducing bonds in this grade range is too complex. We disagree. If bonds are not mentioned, students are left wondering why we don’t fall through
the floor, and there is no good account of melting and boiling and evaporation.
(33) In this grade range, no distinction is made between atoms and molecules. Students may be told some particles are atoms and some are molecules; they will learn about that in
the next grade. Molecular velocity distribution is ignored; in the particulate model, all molecules move at the same speed. Vacuum is mentioned but it is not a salient part of
the model in this grade range.
(34) The point about the distance between particles in solids vs. liquids is very important. It is a very prevalent misconception that particles are (much) further apart in the liquid
than the solid state.
Authors and Reviewers
Dr. Marianne Wiser, Clark University, Massachusetts (author)
References
None provided at this time.
Massachusetts Department of Elementary and Secondary Education
Properties & Transformations of Matter 28
Atomic Structure & Periodicity
November 15, 2010
Atomic Structure & Periodicity
Concept and Skill Progression for Atomic Structure and Periodicity
The learning progression for atomic structure and periodicity centers on the development of two ideas about the structure and properties of matter: the nuclear model of atomic
structure and the identity and relationship of elements arranged in the Periodic Table. These ideas develop in a complementary fashion: as more sophisticated representations of
atomic structure evolve to include charged particles, forces and electron configurations, students are able to explain and predict interactions between and within atoms, and can
discern patterns and trends in the way elemental substances are classified (periodicity).
NARRATIVE STORYLINE
Initial Ideas1
Before instruction, students in the early elementary grades recognize that objects are made of different kinds of materials. While certain materials have a defined purpose and
application, it is possible to build different things from the same materials and to build the same type of product from different materials. Students realize that certain materials are better
than others for a given purpose. Students likely describe the structure of matter macroscopically based on their direct observations (i.e., a macroscopic level), using characteristics that
they can directly observe and measure (e.g., color, weight, size, and texture). They are unlikely, however, to be able to explain the source of the properties. Students understand that
objects are made of matter, and can classify things as matter using the criteria that matter takes up space and has weight. Students may, however, have difficulty classifying certain
materials as matter (e.g., gases, pieces that are too small to see). Students start building ideas about conservation of matter and should typically believe that there may be pieces of
matter that are too small to see. Students often underestimate the range of sizes in the sub-macroscopic world. They may believe that atoms are of similar size, or just slightly smaller
than a cell.
Conceptual Stepping Stones
Early Middle School students can consider what different materials are made of and how to define and distinguish between different substances. Students can use a basic particulate
model for the structure of matter that includes particles of matter that are too small to see and are in constant motion to explain a range of phenomena (e.g., phase changes, diffusion, and
dissolution). Students hold a model of atomic structure consisting of a sphere with no components 2. They can explain the hierarchy of the structure of matter—atoms and molecules are
the particles that make up all substances,3 which in turn are the building blocks of the materials and objects we observe. Students develop criteria for characterizing and distinguishing
between substances at an atomic level. Students understand that pure substances can be classified as elements, which are made up of just one type of atom, and compounds, which
consist of more than one kind of atom. The type(s), number(s) and arrangement of atoms determines the identity of a substance.
Late Middle School/Early High School students build upon the basic particle model of matter and the idea of elements to develop more sophisticated models for the structure and
properties of matter, which in turn leads to the Periodic Table and the trends it predicts. Students develop a nuclear model of atomic structure that incorporates positively charged
protons, negatively charged electrons and neutrons, which have no charge. This basic model includes protons and neutrons packed together to make up a dense, relatively massive
nucleus that represents most of the mass of the atom, with the electrons surrounding the nucleus occupying most of the volume of the atom. Students can describe models for atomic
structure that include electrons distributed in levels around the nucleus. They realize that the electrons in the outermost, or valence, level of an atom determine how it interacts with
other atoms. With a nuclear model of atomic structure, students can connect the structure of atoms with the elements listed in the Periodic Table. Students understand that the number of
protons in the atom determines the type of element it is, and defines the atomic number on the Periodic Table. Students can explain that the pattern in which the elements are arranged
on the Periodic Table relates to properties of the elements
Culminating Scientific Ideas
High School students build upon the nuclear model of atomic structure to develop a model for electron distribution to further explore the trends of the Periodic Table and to explain the
role of electrons in interactions between and within atoms. Students understand that an atom or group of atoms is not always neutral, but can hold an electrical charge. Students can
explain the process of ionization as electrons being added or removed from the valence shell. Students apply models of attraction and repulsion between the positively charged
nucleus and the surrounding electrons to explain the trends predicted by the Periodic Table for many properties. In order to explain a broader range of interactions among atoms and
molecules (e.g., intermolecular forces) students can apply a model of atomic structure where electrons are distributed in compartments of space around the nucleus that represent the
probability of electron density. Thus, electrons are better modeled as “clouds” of electron density than as point charges moving in solar system-like orbitals around the nucleus.4
Massachusetts Department of Elementary and Secondary Education
Atomic Structure & Periodicity
29
Atomic Structure & Periodicity
November 15, 2010
Lower Anchor
Reflective of student concepts
Atomic Structure & Periodicity
Upper Anchor
Reflective of science concepts
Reconceptualization
CONCEPT & SKILL DETAILS
Initial Ideas
Before instruction, students often believe
and can:
Conceptual Stepping Stones
Culminating Scientific Ideas
Students who view the world in this way believe and can:
Students who fully understand this topic believe and
can:
Grades 6-7
Grades 8-95
High school (Grades 10-12)
Models of atomic structure
Models of atomic structure
Models of atomic structure
Models of atomic structure
Students can describe the structure of
matter macroscopically based on their
direct observations (i.e., a
macroscopic level).
Students can use a particulate model for
matter to explain real world phenomena
(e.g., water cycle, smells traveling across
the room, dye diffusing).
Students understand that objects are
made of matter, and can classify
things as matter using the criteria that
matter takes up space and has weight.
Students can explain how a particulate
model of matter helps explain the
conservation of mass through various
transformations of matter (e.g., phase
changes, dissolution, chemical reactions).
[link to particle model of matter]
Pre-instruction (Elementary)
Students have ideas about
conservation of matter and typically
believe that there may be pieces of
matter that are too small to see.
Possible Misconceptions:
Students may have difficulty
classifying certain materials as matter
(e.g., gases, pieces that are too small
to see; Smith, Wiser, Anderson, &
Krajcik, 1997).
Students may identify solids, liquids,
and gases as three types of materials
(Johnson, 2010).
Students may believe atoms look and
behave like a solar system (Griffiths &
Preston, 1992; Harrison & Treagust,
1996).
Students can estimate the relative size of
the particles (atoms) that make up matter
to familiar objects or references (e.g., a
cell, a millimeter).
Students can differentiate a substance
(kinds of matter which are homogeneous
and have invariant properties) from a
material, which include substances and
mixtures of substances.6
As students develop an understanding of
how to characterize properties of
substances3 (e.g., melting point, density,
hardness, conductivity), it is important
that they can differentiate those properties
from the properties of the individual
particles (atoms or molecules) that make
Massachusetts Department of Elementary and Secondary Education
Students hold a nuclear model of atomic
structure.10
Students can use a model of electrostatic
attractions and repulsions11 between the
electrons and nucleus to explain the basic
structure of the atom.
Students can interpret representations of
atoms that indicate the number of protons,
neutrons and electrons and connect them
with the corresponding element on the
Periodic Table.12
Students can provide historical
experimental evidence that supports both
nuclear and electrostatic models for
atomic structure and explain how the
evidence supports them.
Students can predict whether and in what
combination two elements may combine
based upon the number of electrons in
their valence shell.13
[Link to bonding]
Students can describe protons and
neutrons as the primary determinants of
atomic mass.
Students can describe and distinguish between
different models of atomic structure (i.e., solar
system, Bohr, electron cloud) and determine for
what purposes each might be useful.13
Students realize that neutral atoms of the same
element all have the same number of protons
and electrons, but can have different numbers of
neutrons. Students can explain why the atomic
mass for each element is not a whole number.
Students can explain how ions form and why it
is electrons that are added or removed during
the process of ionization. Students can predict
the most likely charge of the ionized form of an
element based upon its location on the Periodic
Table.13
Students should understand the spectroscopic
evidence used to differentiate different types of
atoms (elements) and connect it to atomic
structure. Students can explain why absorption
and emission spectra provide evidence that
electrons in an atom have discrete energy
levels. Students can explain why each element
has a unique absorption and emission spectrum.
Students can use the electron cloud model and a
model of attraction and repulsion to explain
how electrons of neutral atoms can shift
Atomic Structure & Periodicity
30
Atomic Structure & Periodicity
Students may confuse atoms with cells
because they are both referred to as
“fundamental building blocks” of
matter (atoms) of living organisms
(cells) and both atoms and cells have
nuclei (Horton, 2007).
Students may believe that atoms are
made of “atoms” (Renström et al.
1990).
Students often underestimate the range
of sizes in the sub-macroscopic world.
They may believe that atoms are of
similar size, or just slightly smaller
than a cell (Griffiths & Preston, 1992).
Students may think that every material
is a single substance (Johnson, 2000).
November 15, 2010
up a substance.7
[Link to properties of matter]
As students are developing a model for
the structure of matter, 8 they begin to
consider what makes substances different.
Students can explain that the type of
atoms and their arrangement affect the
identity and properties of a substance.9
Possible Misconceptions:
As they are developing a particulate
model of matter, students often use the
terms atoms, molecules and particles
interchangeably (Harrison & Treagust,
1996).
It is common for students to believe that
atoms and molecules share the same
properties as the bulk substance (e.g.,
Albanese & Vincentini, 1997; Ben-Zvi,
Eylon, & Silberstein, 1986).
Possible Misconceptions:
Students may believe that a charged
object can have only one kind of charge
(Horton, 2007).
Students often do not prioritize the
relative masses of the proton, neutron and
electron (Cokelez & Dumon, 2005).
Atomic Structure & Periodicity
spontaneously, or in response to an external
electromagnetic field to create an imbalance of
charge–an induced dipole.
Students can explain how neutral atoms can be
attracted to each other through electromagnetic
interactions (induced-dipole
interactions/intermolecular forces).
[Link to bonding]
Possible Misconceptions:
Students may believe that:
 Classical mechanics effectively and
accurately predicts and describes the
behavior of matter under all conditions and
scales (Kalkanis, Hadzidaki, & Stavrou,
2003).
 Electrons move around the nucleus in
orbitals like planets around the solar system
(Griffiths & Preston 1992; Unal & Zollman,
1999).
 An electron cloud consists of a mass of
suspended electrons much like water droplets
in a cloud above the earth (Horton, 2007).
Students may believe that:
 Atoms containing equal numbers of protons
and neutrons are more stable.
 Neutrons neutralize the repulsion between
protons within the atomic nucleus.
 They may also confuse isotopes and
allotropes.
(Schmidt, Baumgartner, & Eybe, 2003)
To explain ionization, students may rely on
other models (e.g., the octet rule or filled and
half-filled shells)(Tan, Taber, Liu, Coll,
Lorenzo, Li, Goh, & Chia, 2008).
Massachusetts Department of Elementary and Secondary Education
Atomic Structure & Periodicity
31
Atomic Structure & Periodicity
November 15, 2010
Atomic Structure & Periodicity
Elements and periodicity
Elements and periodicity
Elements and periodicity
Students can recognize that objects are
made of different kinds of materials.
Students can explain the effect of
changing the type of atoms and their
arrangement on the identity and
characteristics of a substance.
[Link to properties of matter and particle
model of matter]
Students can explain the relationship
between atom characteristics (i.e., number
of protons, number of valence electrons)
and the pattern observed in the Periodic
Table.
Students can provide examples of
building different things from the
same materials and building the same
type of product from different
materials.
Students realize that certain materials
are better than others for a given
purpose.
Students can evaluate atomic and
molecular level models of substances to
distinguish between elements and
compounds.
Possible Misconceptions:
When first introduced to the idea of
elements, students may believe that all
raw materials are elements (e.g., wool,
wood, salt; Driver, Squires, Rushworth, &
Wood-Robinson, 1999).
Students may believe that any
representation that includes multiple
types of atoms is a mixture (Kind, 2004).
Students can predict whether and in what
combination two elements may combine
based upon their location on the Periodic
Table.13
[Link to Bonding]
Students can represent the electron
configurations of elements based upon
their location on the Periodic Table.14
Based upon their location on the Periodic
Table, students should be able to predict
into what class an element falls (i.e.,
metal, non-metal, metalloid/semi-metal or
noble gas).
Possible Misconception:
Students may have difficulty explaining
periodic trends; students may often rely
on memorization to explain periodic
trends (Abraham, et. al., 1994).
Elements and periodicity
Students can apply a model involving
electrostatic attraction and repulsion to explain
the relative effective nuclear charge for
elements across a period.
Students can apply a model involving shielding
of electrostatic attractions and repulsions within
an atom to explain many of the trends predicted
by the Periodic Table (e.g., electronegativity,
electron affinity, atomic radius, ionization
energy), both across at period and down a
group.
Students can use the Periodic Table to predict
whether a molecule will have a dipole.15
[Link to Bonding: dipole-dipole interactions]
Students can use periodic trends to predict the
type and relative strength of intermolecular
interactions.16
Possible Misconceptions:
Students may have difficulty connecting atomic
structure and properties with the periodic table
(Abraham et. al., 1992).
Students may believe that the nucleus attracts
all electrons around it equally (Taber, 1998).
Grades
Pre-instruction
Grades 6-7
Grades 8-9
High school (Grades 10-12)
Key Vocabulary
atom, characteristic, substance, material,
element, compound, molecule, matter,
particular model, conservation of mass,
atomic model, transformation of matter
Massachusetts Department of Elementary and Secondary Education
electrostatic attraction and repulsion,
electron, nucleus, Periodic Table,
valence electron/shell, atomic mass,
electron configuration, metal, nonmetal, metalloid, noble gas, proton
ion, ionization, charge, absorption and emission
spectra, energy level, intermolecular forces,
electronegativity, atomic radius, ionization
energy, period, group, dipole, induced dipole,
effective nuclear charge, electron cloud model,
electromagnetic field, neutron, atomic mass
Atomic Structure & Periodicity
32
Atomic Structure & Periodicity
November 15, 2010
Atomic Structure & Periodicity
Notes
(1) This is a brief summary of ideas that students develop through the elementary grades as they work towards developing a particulate model of matter based primarily on the
work of Smith and colleagues (2006). [See the concept and skill progression for Matter and its Transformations for more detail.] One of the core ideas of science involves
answering what are the things around us made of and what determines their properties.
(2) It is unproductive to introduce the details of atomic structure too early because a more sophisticated model of atomic structure is not necessary to explain phenomena at this
level. Unnecessary details can hinder development of students’ understanding of the central ideas.
(3) The concept of a substance lies at the heart of understanding chemistry. However, the concept of a substance is not innate; it is an abstract scientific idea that needs to be
learned. More instinctively, everyday thinking assigns identity to a sample of stuff by its history (origin and what has happened to it) rather than here and now properties.
Without the concept of a substance, ‘elements’ and ‘compounds’ cannot be understood as two types of substance and ‘mixtures’ as mixtures of substances. Confusion between
‘elements’, ‘compounds’ and ‘mixtures’ follows (a ‘compound’ is made from more than one thing which sounds like a ‘mixture’). Without the concept of a substance students
cannot conceive of the possibility of chemical change; substances changing into other substances.
(4) LIMIT: The use of quantum mechanical ideas is purely qualitative. It is just important for students to realize that an alternative model to classical mechanics is needed to
explain atomic structure and interactions). Research has shown that students can apply both a solar system/Bohr model of the atom and an electron cloud model when
instruction emphasizes that they are models and what the implications of being models are.
(5) This and the high school level could also correspond to early and later high school courses. The early middle school level would then become just middle school (grades 6-8).
(6) ‘Materials’ and ‘substances’ are often interchanged without recognising the hierarchical relationship (materials covers substances and mixtures of substances).
(7) Left unsaid is how properties can be used to distinguish between a pure sample of a substance and a mixture of substances. This is the first step towards recognising a
substance. Melting behaviour can do this for ‘unknown’ materials (an exact melting point = a substance, non exact = mixture (e.g. chocolate)). Density can identify a substance
but cannot distinguish between mixtures and substances. At middle school level, hardness and conductivity do not help with the distinction. When ideas of atoms are
introduced, the distinction between the atom and the substance is often not emphasized: more than one substance can be made from one type of atom (e.g. oxygen and ozone).
‘Element’ is often used with two meanings that are not distinguished; students attribute the properties of a substance to the atom. (Introducing the Periodic table as a table of
substances may contribute to misconceptions12.
(8) LIMIT: At this point students’ atomic model is limited to an atom as sphere with no components.
(9) Try to avoid linking this to “motion” of atoms or molecules as that implies the properties of state; a ‘solids, liquids and gases’ framework. Generic properties of states are not
different for substances since any substance can be in any of the three states (excepting decomposition).
(10) This basic model includes protons and neutrons packed together to make up a dense, relatively massive nucleus that represents most of the mass of the atom, with the
electrons surrounding the nucleus occupying most of the volume of the atom. Students can describe models for atomic structure that include electrons distributed in levels
around the nucleus.
(11) A model of electrostatic attraction and repulsion provides a powerful explanatory framework for the structure and properties of matter (including bonding). A focus on the
model may help prevent memorization of categories and classifications.
(12) In line with longstanding practice, the Periodic Table is introduced with ‘elements’ as substances, rather than with regard to atomic structure. Although Mendeleev’s original
table was of substances, the modern table is of atoms and it could be valuable to introduce it in this way. Starting with substances increases the danger of conflating atoms and
substances under ‘element’. This can lead to the misconception of atoms having the properties of the element (substance). The properties of ‘oxygen’ are the properties of
diatomic molecules, not oxygen atoms. Individual atoms are not metal or non-metal. Ideas of structure and types of bonding are needed to connect atoms to the observed
elementary substances.
(13) LIMIT: only main group elements (Groups I-VIII).
(14) LIMIT: only for periods 1-3.
(15) LIMIT: main group elements only.
(16) LIMIT: Students do not need a quantum mechanical probabilistic model to explain interactions among atoms and molecules. A classical probabilistic model is also functional
for students at this level. Quantum mechanical ideas are not always specifically mentioned, but ideas such as intermolecular forces and energy levels generally are. A decision
Massachusetts Department of Elementary and Secondary Education
Atomic Structure & Periodicity
33
Atomic Structure & Periodicity
November 15, 2010
Atomic Structure & Periodicity
must be made to what level these ideas should be “black boxed:” (1) terms introduced with little explanation or (2) introduce the need for a different model to explain the
behavior of systems at this scale. Explain how classical models failed and provide connection to a model when using terms ‘energy level,’ etc., or use the terms qualitatively.
Authors and Reviewers
Shawn Stevens, University of Michigan, Michigan (author)
Dr. Phil Johnson, Durham University, England (reviewer)
References
Abraham, M. R., Grzybowski, E. B., Renner, J. W., & Marek, E. A. (1992). Understanding and misunderstandings of eighth graders of five chemistry concepts found in textbooks.
Journal of Research in Science Teaching, 29(2), 105-120.
Abraham, M. R., Williamson, V. M., & Westbrook, S. L. (1994). A cross-age study of the understanding of five chemistry concepts. Journal of Research in Science Teaching,
31(2), 147-165.
Albanese, A. & Vincentini, M. (1997). Why do we believe an atom is colourless? Reflections of the teaching of the particle model. Science & Education, 6, 251-261.
Ben-Zvi, R.; Eylon, B.; and Silbestein, J. (1986). Is an atom of copper malleable? Journal of Chemical Education 63(1), 64-66. (Referred to in Nakhleh (1992).)
Cokelez, A., & Dumon, A. (2005). Atom and molecule: Upper secondary school French students' representations in long-term memory. Chemistry Education: Research and
Practice, 6(3), 119-135.
College Board, The, (2009). Science College Board Standards for College Success, The College Board
Driver, R., Squires, A., Rushworth, P., & Wood-Robinson, V., (1999). Making sense of secondary science: Research into children's ideas. London: Routledge.
Griffiths, A. K., & Preston, K. R. (1992). Grade-12 students' misconceptions relating to fundamental characteristics of atoms and molecules. Journal for Research in Science
Teaching. 29(6), 611-628.
Harrison, A. G., & Treagust, D. F. (1996). Secondary students' mental models of atoms and molecules: Implications for teaching chemistry. Science Education, 80(5), 509-534.
Horton, C. (2007). Student alternative conceptions in chemistry. California Journal of Science Education, VII(2).
Johnson, P. M. (2000). Children's understanding of substances. Part 1: Recognizing chemical change. International Journal of Science Education, 22(7), 719-737.
Johnson, P. M.. & Tymms, P. (2010).Using Rasch modeling on a large cross-sectional data-set to test for a learning progression in chemistry suggested by a previous, small-scale,
three year longitudinal study. Presented at the National Association for Research on Science Teaching: Philadelphia, PA.
Kalkanis, G., Hadzidaki, P., & Stavrou, D. (2003). An instructional model for a radical conceptual change towards quantum mechanics concepts. Science Education, 87, 257-280.
Kind, V. (2004). Beyond Appearances: Students’ misconceptions about basic chemical ideas. 2nd Edition, School of Education, Durham University, UK. Self-published; available
at < http://www.chemsoc.org/pdf/LearnNet/rsc/miscon.pdf >
Renström, L., Andersson, B., & Marton, F. (1990). Students' conceptions of matter, Journal of Educational Psychology 82, 555-569.
Schmidt, H.-J., Baumgärtner, T., & Eybe, H. (2003). Changing ideas about the Periodic Table of Elements and students’ alternative concepts of isotopes and allotropes. Journal of
Research in Science Teaching, 40(3), 257-277.
Smith, C. L., Wiser, M., Anderson, C. W. & Krajcik, J., (2006). Implications of research on children’s learning for standards and assessment: A proposed learning progression for
matter and the atomic molecular theory. Measurement: Interdisciplinary Research and Perspectives, 4, 1-98.
Taber, K.S. (1998). The sharing out of nuclear attraction, or 'I can't think about physics in chemistry', International Journal of Science Education 20 (8), 1001-1014.
Tan, K. C. D., Taber, K. S., Liu, X., Coll, R. K., Lorenzo, M., Li, J., Goh, N. K., & Chia, L. S. (2008). Students’ conceptions of ionization energy: A cross-cultural study.
International Journal of Science Education, 30(2), 263-283.
Unal, R., & Zollman, D. (1999). Students' description of an atom: a phenomenographic analysis. Downloaded from http://perg.phys.ksu.edu/papers/vqm/AtomModels.pdf
Massachusetts Department of Elementary and Secondary Education
Atomic Structure & Periodicity
34
Chemical Bonding & Reactions
November 15, 2010
Chemical Bonding & Reactions
Concept and Skill Progression for Chemical Bonding and Reactions
The progression is organized into six core ideas: Distinguishing change of state from chemical reactions; Achieving stability and equilibrium; Molecular structure and
intermolecular forces; Chemical kinetics; and Conservation of mass in reactions. Conceptual learning begins in middle school then progresses to the early part of a high school
course, and then ends with culminating concepts at the latter portion of a high school course.
NARRATIVE STORYLINE
Initial Ideas
Before instruction students know when a new material is made by combining two or more materials; it has properties that are different from the original materials. Students are likely to
have exposure to a ‘particle model’ perspective but they will generally pay more attention to macroscopic observations and fail to explain reactions sub-microscopically.
Conceptual Stepping Stones
Middle school students can distinguish between change of state and chemical change. They can cite observable phenomena as indicators of a chemical change. Students can describe the
attractive forces between particles in a substance and understand how the strength of these attractions helps to explain many physical properties of substances, including why different
substances exist as solids, liquids or gases at given temperatures. They begin to think sub-microscopically about how the physical properties of materials are determined by the strength
of the attractions between particles. They recognize that in chemical reactions, the atoms present in the reactants are all present in the products, but the atoms are found in different
combinations (bonds) that result in the formation of different substances. No matter how substances within a closed system interact with one another, or how they combine or break apart,
the total weight of the system remains the same and the number of atoms stays the same no matter how they are rearranged.
High School (early in course): Students can translate among macroscopic, symbolic, and molecular level representations of states and describe the relative arrangement of particles in
each. They differentiate between changes of state and chemical reactions, understanding that reactions involve rearrangements of atoms to produce new substances with different
properties. Students understand that chemical bonds are the result of equal attraction and repulsion between atoms. They describe bonding as a continuum from purely non-polar covalent
bonds to ionic bonds, and use electronegativity to predict the polarity of bonds. They can use valence-shell electron-pair repulsion theory (VSEPR) to predict the molecular geometry of
simple molecules and relate that to molecular polarity. They describe how intermolecular forces between molecules are determined by the shape and polarity of the molecules. Students
can predict chemical formulas based on the number of valence electrons of the constituent atoms. Students observe that reactions take place faster if the mixture is stirred or reactants are
finely divided. They may, however, consider that a chemical reaction may not take place without the influence of mechanical factors. Students know that some factors influence particle
motion and therefore believe these factors also influence rate of reaction.
Culminating Scientific Ideas
High School (later in course): Students describe how the structures of compounds determine their properties and reactivity. Students can classify chemical reactions and predict different
types of chemical reactions from the structure and properties of the reactants involved. They understand that chemical reactions are usually the result of the increase in the overall
stability of a system. Students understand that reactions are generally in a constant state of equilibrium of forming reactants and products. They predict chemical formulas of products
based on the number of valence electrons of the constituent atoms in reactants. Students understand that an input of energy is needed to initiate a reaction. Students comprehend that a
mechanical event is not a pre-requisite for a chemical reaction, but it can expedite the rate of reaction. They can explain how, using molecular models, temperature, concentration and
pressure affect the rate of reaction because of their effect on particle motion and collisions between reactant or product particles. They also can explain how a catalyst affects the rate of
reaction. Students can demonstrate the principle of conservation of mass in reactions by balancing chemical equations and using the mole concept to complete basic stoiciometry
calculations.
Massachusetts Department of Elementary and Secondary Education
Chemical Bonding & Reactions
35
Chemical Bonding & Reactions
November 15, 2010
Lower Anchor
Reflective of student concepts
Reconceptualization
Chemical Bonding & Reactions
Upper Anchor
Reflective of science concepts
CONCEPT & SKILL DETAILS
1
Initial Ideas
Conceptual Stepping Stones2
Culminating Scientific Ideas
Before instruction, students often
believe and can:
Students who fully understand this topic believe and can:
Students who fully understand this topic believe and
can:
Pre-instruction
Middle school
High school (early in course)
High school (later in course)
Distinguishing change of
state from chemical reactions
Distinguishing change of state from
chemical reactions
Distinguishing change of state from
chemical reactions
Types of chemical reactions
Students know when a new
material is made by combining
two or more materials; it has
properties that are different from
the original material.3, 4
Recognize that a substance has a melting
point and a boiling point, both of which
are independent of the amount of the
sample.
Differentiate between changes of state and
chemical reactions. Chemical changes involve
rearrangements of atoms in molecules10 to
produce new substances with different
properties while changes of state do not.
Different types of chemical reactions result from
the structure and properties of the reactants
involved. Classify chemical reactions as
synthesis (combination), decomposition, single
displacement, double displacement, and
combustion.13 Predict the type of reaction based
on the structure and properties of the reactants.
Students take ‘solids, liquids and
gases’ literally. They think these
are three different types of
materials.5
Explain why solids, liquids and gases
have different physical properties (e.g.,
shape, volume or thermal expansion) at
room temperature based on a particle
model of substances.6, 7
[link to conservation of mass]
In chemical reactions, the atoms present
in the reactants are all present in the
products, but the atoms are found in
different combinations (bonds) that result
in the formation of different substances. 8
Properties11
Translate among macroscopic, symbolic, and
atomic–molecular level representations of
states. Describe, using representations, the
relative arrangement of particles in solids,
liquids and gases.12
Explain why gases expand to fill a container of
any size, while liquids flow and spread out to
fill the bottom of a container and solids hold
their own shape. Justification includes a
discussion of particle motion and the attractions
between the particles.11
A chemical change is often accompanied
by observable phenomena such as
precipitation, gas evolution, change in
temperature or change in color.
However, the chemical change is
sometimes difficult to detect through
direct observation.9
Massachusetts Department of Elementary and Secondary Education
Chemical Bonding & Reactions
36
Chemical Bonding & Reactions
Achieving stability and
equilibrium
November 15, 2010
Achieving stability and equilibrium
[Link to periodicity, elements and
compounds, particulate model of
matter.]
Possible Misconceptions:
Students may believe that atoms need
“filled shells” or that chemical reactions
occur so that atoms can obtain filled
shells (Taber, 2002).
Achieving stability
The atoms of many elements are more stable
when bonded with other atoms.14
Chemical bonds are the result of equal
attraction and repulsion between atoms. Filled
orbitals are the result of this equilibrium, not
the cause.15
Energy is required to form bonds.
Energy is released when a bond is
formed (Taber, 2002).
Bonding is a continuum from purely non-polar
covalent bonds, through polar covalent bonds, to
ionic bonds.16
There are only two kinds of bonds:
covalent and ionic bonds. Hydrogen
bonds, then are not real bonds (Taber,
2002).
Use electronegativity to predict the polarity of
bonds. [link to periodicity]
Equal sharing of electron pairs occurs in
all covalent bonds (Taber, 2002).
Chemical Bonding & Reactions
Achieving equilibrium
Chemical reactions are usually the result of the
increase in the overall stability of a system when
reactants form products.
Students should be able to describe, using
graphic representations, the types of energy
changes (e.g., potential energy transforms into
kinetic energy during bond formation; change in
potential energy for an exothermic or
endothermic reaction) that may occur in a
system of reacting molecules when a bond
between atoms or ions is either weakened or
strengthened.18
Reactions are not “done” but are in a constant
state of equilibrium of forming reactants and
products.
Identify how hydrogen bonding in water affects
a variety of physical, chemical, and biological
phenomena (e.g., surface tension, capillary
action, density, boiling point).
Modeling results of bonding
Predict chemical formulas based on the number
of valence electrons of the constituent atoms.
[link to periodicity]
Modeling results of reactions
Predict chemical formulas of products based on
the number of valence electrons of the
constituent atoms in reactants.
Represent bonded atoms with Lewis dot
structures for compounds.
Name and write the chemical formulas for
simple compounds.17
Molecular structure and
intermolecular forces19
Molecular structure and
intermolecular forces
[Link to electrical charge interactions]
Molecular structure and intermolecular
forces
There are attractive forces between particles in
a substance. The strength of these attractions
Massachusetts Department of Elementary and Secondary Education
Chemical Bonding & Reactions
37
Chemical Bonding & Reactions
The physical properties of materials are
determined by the strength of the
attractions between particles.20
Possible Misconceptions:
The shapes of molecules are due only to
the repulsion between atoms or due only
to the repulsion between non-bonding
pairs of electrons (Taber, 2002).
Intermolecular forces are forces within
molecules (Taber, 2002).
Non-polar molecules are formed when
the constituent atoms have similar
electronegativities (Taber, 2002).
November 15, 2010
Chemical Bonding & Reactions
helps to explain many physical properties of
substances, including why different substances
exist as solids, liquids or gases at given
temperatures.21
The shapes of molecules are due in part to the
repulsion between non-bonding electron pairs
and in part to the repulsion between bonding
electron pairs.
Intermolecular forces are forces between
molecules and are determined by the shape and
polarity of the molecules.
Use valence-shell electron-pair repulsion theory
(VSEPR) to predict the molecular geometry
(linear, trigonal planar, and tetrahedral) of
simple molecules.
Use VSEPR electronegativity to predict the
polarity of molecules.
Non-polar molecules can be formed from atoms
with very different electronegativities.
Chemical kinetics
Chemical kinetics
Chemical kinetics
Activation energy
Activation energy
Possible Misconceptions:
Students may believe that activation energy is
the energy released after a reaction (Cakmakci,
2005). Further, some students consider
activation energy the kinetic energy of product
molecules. As a result the reaction with the
higher activation energy occurs faster
(Cakmakci, 2005).
Activation energy
Students understand that an input of energy is
needed to initiate a reaction. The amount of
energy required is called the activation
energy barrier.24
Rate of reactions22
Rate of reactions
Students know some critical aspects of ‘rate,’
‘reaction,’ ‘mechanism’ and ‘speed’ and may
use such knowledge to describe the similarities
and differences of the concept of ‘rate of
reaction.’
Rate of reactions
Students understand the difference between the
rate of reaction and the reaction time (e.g.
Cakmakci, 2005; Taştan, Yalçınkaya, & Boz,
2009).
Massachusetts Department of Elementary and Secondary Education
Chemical Bonding & Reactions
38
Chemical Bonding & Reactions
November 15, 2010
Possible Misconceptions:
Students are often confused between the
concept of rate of reaction and reaction time
(e.g., Cakmakci, 2005; Taştan, Yalçınkaya, &
Boz, 2009). They may think that at the
beginning of a reaction, reactant molecules are
far away from each other; therefore the reaction
rate is zero at the beginning. During a period of
time, interaction of molecules increases and as a
result the reaction rate increases (e.g.,
Cakmakci, 2005; Taştan, Yalçınkaya, & Boz,
2009). They may also believe the reaction rate
is constant as time passes, because reaction rate
does not depend on time; time does not change
reaction rate (e.g., Cakmakci, 2005; Taştan,
Yalçınkaya, & Boz, 2009).
Chemical Bonding & Reactions
Using a particle model, students represent the
rate of reaction sub-microscopically,
symbolically, or mathematically (e.g.,
Cakmakci, 2005; Ebenezer & Erickson, 1996).
[Link to chemical bonding and intermolecular
forces]
Students may think that reaction rate is the time
required for a reaction to be completed or
reaction rate is the amount of energy needed to
initiate a reaction or reaction rate is equal to the
formation energy of products (Cakmakci, 2005;
Nakipoğlu et al., 2002; Taştan, Yalçınkaya, &
Boz, 2009).
Factors influencing rate of
reaction
The effect of mechanical factors
Possible Misconceptions:
Students frequently observe that mechanical
factors such as shaking, stirring, crushing
(surface area) etc. have a role in a
heterogeneous mixture, and that reactions take
place faster or more rapidly if the mixture is
stirred or reactants are finely divided. But
students may believe that stirring or mechanical
factors (e.g., surface area) affect all types of
reactions in both homogenous and
heterogeneous environments (Cakmakci,
2005).23 Further, students may consider that a
chemical reaction may not take place without
the influence of mechanical factors.
Massachusetts Department of Elementary and Secondary Education
The effect of mechanical factors
Students know that mechanical factors such as
shaking, stirring, crushing (surface area) etc.
effectively increase the rate of reaction in
heterogeneous environments. Students
comprehend that a mechanical event is not a prerequisite for chemical reaction or rate of
reaction, but it can expedite the rate of reaction.
Chemical Bonding & Reactions
39
Chemical Bonding & Reactions
November 15, 2010
The effects of temperature, pressure and
concentration
Students know that some factors such as
temperature, pressure and concentration
influence particle motion and therefore believe
these factors also influence rate of reaction.
Possible Misconceptions:
They may, however, reverse relationships. (e.g.,
Cakmakci, 2005; Çalık & Ayas, 2005). Or the
more concentration increases, the more time is
needed to yield reaction products (Nakipoğlu et
al., 2002).
Students often believe that exothermic reactions
occur faster because they do not need energy to
occur or because they have a lower activation
energy. They may also think that reactions that
take place at the same temperature have equal
kinetic energy, thus the rate of reactions would
be the same (e.g. Cakmakci, 2005).
The effect of a catalyst
Even though students comprehend meanings of
‘catalyst’ or ‘enzyme,’ they may believe that a
catalyst does not affect or does not change the
rate of a reaction (e.g. Cakmakci, 2005;
Nakipoğlu et al. 2005).
Chemical Bonding & Reactions
The effects of temperature, pressure and
concentration
Using ‘kinetic theory’ and a particle model
students comprehend that temperature,
concentration (including concentration of
reacting species) and pressure affect dissolution
phenomena because of their effect on particle
motion and collisions between reactant or
product particles (Nakipoğlu et al., 2002). For
example, if temperature increases, kinetic
energies of particles increase, increasing
collisions between particles with enough energy
to result in an increase in rate of reaction. In the
case of gases, the concentration is proportional
to the pressure, so an increase in pressure
increases the probability of collisions between
particles with enough energy to result in an
increase in rate of reaction.
[Link to kinetic theory, states of matter and gas
laws]
The effect of a catalyst
Students know that a catalyst affects the rate of
reaction by providing another mechanism or
pathway with lower activation energy for the
reactants to form products.
Students comprehend that a catalyst does not
commence or end a reaction. Nor is it not used
up in reactions because it is taken up in one step
and re-formed in a later step.
Conservation of mass in
reactions
Conservation of mass in reactions
Conservation of mass in reactions
No matter how substances within a
closed system interact with one another,
or how they combine or break apart, the
total weight of the system remains the
same and the number of atoms stays the
same no matter how they are rearranged
(AAAS, 1993).
Balance chemical equations by applying the
laws of conservation of mass and constant
composition.
Massachusetts Department of Elementary and Secondary Education
Because the mass of an atom is very small, the
mole is used to translate the mass of an atom to
the macroscopic level. The mass of a mole of
Chemical Bonding & Reactions
40
Chemical Bonding & Reactions
November 15, 2010
[Link to particulate model of matter]
Chemical Bonding & Reactions
any substance is equal to its formula mass in
grams.25
Use the mole concept to determine the number
of particles and the molar mass of elements and
compounds.
Calculate the mass-to-mass stoichiometry for a
chemical reaction.
Determine percent compositions, empirical
formulas, and molecular formulas.
Grades
Pre-instruction
Middle school
High school (early in course)
High school (later in course)
Key Vocabulary
substance, melting point, boiling point,
physical property, chemical reaction,
atom, reactant, product, chemical
change, precipitation, gas evolution,
attractive force, conservation of mass
polarity, polar, non-polar, covalent bond, ionic
bond, electronegativity, hydrogen bond, surface
tension, macroscopic, atomic, molecular,
element, change of state, catalyst, temperature,
pressure, concentration, rate of reaction,
VSEPR, intermolecular force, Lewis dot
structure, valence electron, chemical formula,
capillary action, stable, bond/ing, equilibrium,
orbital, energy
synthesis (combination), decomposition, single
displacement, double displacement, combustion,
exothermic, endothermic, ion, reaction time,
heterogeneous, dissolution, kinetic energy,
proportional, activation energy, mole, molar
mass, stoichiometry, percent composition,
empirical formula, molecular formula
Authors and Reviewers
Dr. Alan Kiste, University of Michigan, Michigan (contributor)
Dr. Jazlin Ebenezer, Wayne State University, Michigan (contributor)
Dr. David Treagust, Curtin University, Australia (reviewer)
References
American Association for the Advancement of Science (AAAS). (1993). Benchmarks for science literacy. New York, Oxford University Press.
Cakmakci, G. (2005) A cross-sectional study of the understanding of chemical kinetics among Turkish secondary and undergraduate students. Unpublished PhD Thesis. The University of Leeds, UK
Çalık, M. & Ayas, A. (2005). A Comparison of level of understanding of grade 8 students and science student teachers related to selected chemistry concepts. Journal of Research
in Science Teaching, 42(6), 638-667.
Coppola, B. P. and R. G. Lawton (1997). "The University of Michigan Undergraduate Chemistry Curriculum. 2. Instructional Strategies and Assessment." Journal of Chemical
Education 74: 84-94.
Ebenezer J.V. & Erickson, L.G. (1996). Chemistry students’ conception of solubility: a phenomenograpy. Science Education, 80:181–201
Ege, S. N., B. P. Coppola, et al. (1997). "The University of Michigan Undergraduate Chemistry Curriculum. 1. Philosophy, Curriculum, and the Nature of Change." Journal of
Chemical Education 74: 74-83.
Hapkiewicz, A. (1991). "Clarifying Chemical Bonding." The Science Teacher 58(3): 24-27.
Massachusetts Department of Elementary and Secondary Education
Chemical Bonding & Reactions
41
Chemical Bonding & Reactions
November 15, 2010
Chemical Bonding & Reactions
Kolomuç, A. (2009). Animation aided instruction on “rate of chemical reactions” unit in grade 11 in regard to 5E model. Unpublished PhD thesis, Atatürk University, Turkey.
Nakipoğlu, C. , Benlikaya, R. & Kalın, Ş. (2002). Usage of V-diagrams in eliciting pre-service chemistry teachers’ misunderstanding of ‘chemical kinetic’ [Kimya öğretmen
adaylarında "Kimyasal Kinetik" konusu ile ilgili yanlış kavramaların belirlenmesinde V-diyagramlarının kullanılması]. V. Ulusal Fen Bilimleri ve Matematik Eğitimi
Kongresi, METU. http://www.fedu.metu.edu.tr/ufbmek-5/b_kitabi/PDF/Kimya/Bildiri/t179d.pdf
Nahum, T. L., R. Mamlok-Naaman, et al. (2008). "A New "Bottom-Up" framework for teaching chemical bonding." Journal of Chemical Education 85(12): 1680-1685.
Nahum, T. L., R. Mamlok-Naaman, et al. (2007). "Developing a new teaching approach for the chemical bonding concept aligned with current scientific and pedagogical
knowledge." Science Education 91(4): 579-603.
Ozmen, H. (2004). "Some student misconceptions in chemistry: A literature review of chemical bonding." Journal of Science Education and Technology 13(2): 147-159.
Pabuccu, A. and O. Geban (2006). "Remediating misconceptions concerning chemical bonding through conceptual change text." H. U. Journal of Education 30: 184-192.
Peterson, R., D. Treagust, et al. (1986). "Identification of secondary students' misconceptions of covalent bonding and structure concepts using a diagnostic instrument." Research
in Science Education 16: 40-48.
Peterson, R. F. and D. F. Treagust (1989). "Grade-12 students' misconceptions of covalent bonding and structure." Journal of Chemical Education 66(6): 459-460.
Taber, K. (2002). Chemical misconceptions - prevention, diagnosis and cure. Volume 1: Theoretical background. London, Royal Society of Chemistry.
Taber, K. (2002). Chemical misconceptions - prevention, diagnosis and cure. Volume 2: Classroom resources. London, Royal Society of Chemistry.
Taştan, Ö., Yalçınkaya, E. & Boz, Y. (2009). Pre-service chemistry teachers’ ideas about reaction mechanism. Journal of Turkish Science Education (TUSED) (in press)
Tezcan H. &Yılmaz Ü. (2003). The effect of conceptual computer animations and traditional instruction in teaching chemistry on student achievement [Kimya öğretiminde
kavramsal bilgisayar animasyonlari ile geleneksel anlatım yöntemin başarıya etkileri]. Pamukkale University Journal of Faculty of Education, 14(2), 18-32.
She, H.C. (2004). Facilitating changes in ninth grade students’ understanding of dissolution and diffusion through dslm instruction. Research in Science Education, 34, 503-525.
NOTES:
1 Chemistry misconceptions are often not the result of students’ pre-scientific observations of the world around them. Because chemical concepts depend on an understanding of
the atomic level world that is invisible to them, students often have few initial misconceptions about chemical phenomena. Instead the misconceptions listed below often
develop through their school learning via unintentional generalizations or imprecise language in early grades. Students often hold these misconceptions well after high school
graduation, which may indicate that these concepts are either not being challenged at the HS level, or that they are being unintentionally reinforced. Common language around
atoms “wanting” a full shell of electrons as a reason for bonding (Taber, 2002) is an example of the reinforcement of a misconception. Research on learning progressions
suggests that prior knowledge regarding atoms, molecules, and the particulate nature of matter should be tapped prior to discussions of bonding.
2
There is generally limited empirical evidence that suggests which intermediate ideas are productive stepping stones at each level. We have, however, evidence that students can
develop these ideas (citations noted). Also, these intermediate understandings address ideas for which we have some informed hypotheses that lead to the important ideas in the
targeted understanding. In many cases to move from an intermediate understanding to the targeted level of understanding, all connections between ideas need to be consistently
made.
3
College Board, Foundational Knowledge, p. 88.
4
Without the concept of a substance students cannot begin to conceive of the possibility of chemical change; substances changing into other substances. Instead, an emphasis on
‘reversibility’ as a criterion for thinking about changes misses the point since chemical changes can be both irreversible and reversible. Historical thinking is unhelpful. Without
the concept of a substance, ‘elements’ and ‘compounds’ cannot be understood as two types of substance and ‘mixtures’ as mixtures of substances. Confusion between
‘elements’, ‘compounds’ and ‘mixtures’ follows (a ‘compound’ is made from more than one thing which sounds like a ‘mixture’).
5
‘Solids, liquids and gases’ coupled with the absence of the concept of a substance inhibits understanding of the particle theory. It is not clear that the ‘basic’ particles are particles
of substances (and mixtures are mixtures of different substance particles). The model for ‘solids, liquids and gases’ does not explain why different substances have different
melting and boiling points: i.e. different substances coexisting in different states is not explained. This reinforces the misconception of three types of particle having the
macroscopic properties of three types of stuff (solid particles, liquid particles and gas particles). Changes of state (change in particle) are the somewhat confusing, anomalous
behavior of a few materials. Sole emphasis on the kinetic aspects of the particle model gives life to the misconception of particles (unknown) being embedded in the continuous
material. Most significantly, with such misconceptions ‘gases’ still remain a mystery – there is no sense that ‘gases’ are different substances just as much as salt and iron.
Massachusetts Department of Elementary and Secondary Education
Chemical Bonding & Reactions
42
Chemical Bonding & Reactions
November 15, 2010
Chemical Bonding & Reactions
6
While not about molecular shape per se, it allows inference of shape from macroscopic properties (i.e., water is polar and thus has a higher than expected boiling point because it
is bent, not linear). This needs to then be related to microscopic shapes of molecules. College Board standard PS-PE 2.3.4.
7
The ‘solids, liquids and gases’ approach does not distinguish between substances and mixtures of substances. The messy behavior of some mixtures is left unexplained, in
contrast to the simpler behavior of pure samples of substances. The difference between boiling and evaporation below boiling point is not explained. Both are said to be a
change to the gas state, which is confusing since one takes place at a specific temperature and the other at any temperature. That one result in a pure sample in the gas state (the
bubbles) and the other a mixture with air is ignored.
8
College Board, p. 101.
9
College Board, p. 102.
10
Except dipolar or dative bonding.
There is often a distinction made between chemical and physical properties but this is not at all clear in many cases. It is helpful to define any property or reactivity that involves
electrons as chemistry (for example, dissolving). Even melting can be viewed as chemical as it directly relates to the structure of the molecules and their intermolecular forces.
12
These support the later intermolecular forces standards. Ideal gases were purposely left out as they, by definition, have no intermolecular forces. College Board standards CPE.1.5.1 and C-PE.1.5.2.
13
While most general chemistry textbooks written in the last 25 years classify chemical reactions as synthesis, decomposition, single displacement, double displacement, and
combustion, this classification is not general. For example, this classification scheme makes little (if any) sense from the standpoint of organic chemistry. A much more general
scheme is that reactions can be classified as addition, elimination, or substitution reactions or as some combination of those 3 basic types (e.g. addition followed by
elimination). Or, one could get even more general and classify every reaction as an oxidation or reduction (which might have its own advantages as far as getting students to
see reactions as a flow of electrons rather than just having atoms fulfill the octet rule.) Either of those schemes would have the advantage of being ways that real chemists
actually classify reactions. In addition, those schemes describe the actual mechanism of reaction, which the current scheme does not, and they provide the ability to make
predictions.
14
(CB, p. 117)
15
Chemical bonding is the result of a thermodynamically stable equilibrium between attraction and repulsion between atoms. While the octet rule can be used to predict stable
chemical species, it is not the reason for bonding and should be actively discouraged. (Taber 2002)
16
LIMIT: Hybridization is not an expected concept. NOTE: There is a strong trend in most chemistry classes and textbooks to make covalent and ionic bonds two separate
categories rather than simply two ends of a spectrum. This continuum is made explicit here to deemphasize that incorrect distinction. Please refer to College Board standards for
definitions of each type of bond.
17
NOTE: include those that contain the polyatomic ions: ammonium, carbonate, hydroxide, nitrate, phosphate, and sulfate.
18
College Board, C-PE.1.3.1.
19
A useful organizing principle for Chemical Bonding and Chemical Reactions is the notion of “Structure and reactivity.” (Coppola and Lawton 1997; Ege, Coppola et al. 1997).
That is, the structures of all compounds determine their properties and reactivity. And, one can predict the properties and reactivity of new materials by examining differences
in structure with known compounds. Using this organizing principle, the emphasis can be on prediction from a small number of basic concepts (e.g. electronegativity and
VSEPR) rather than memorization of the properties and reactivities of a large number of compounds.
20
College Board, p. 126.
21
College Board, p. 99.
22
There are a few papers discussing student learning of rate of reactions. There is, however, research on alternative conceptions.
23
For example, students may consider that the reaction rate is the same for both reactions (powdered MgO and granulated MgO) because the same amount of substances have been
used or the physical features of substances only affect the rate of dissolving.
24
College Board, Essential Knowledge, p. 131.
25
College Board, Essential Knowledge, p. 128.
11
Massachusetts Department of Elementary and Secondary Education
Chemical Bonding & Reactions
43
Solution Chemistry
November 15, 2010
Solution Chemistry
Concept and Skill Progression for Solution Chemistry
This progression is organized by four major topics: the Physical Characteristics of Solutions; the Solution Process; Interactive Effects; and Solubility Equilibrium. Starting at
middle school, emphasis is placed on mixtures then the particulars of solutions.
NARRATIVE STORYLINE
Initial Ideas
Before instruction students sometimes confuse ‘mixtures’ with ‘solutions,’ and are sometimes confused between the components of a solution. They tend to use types of solutions
interchangeably without using the concept of ‘solubility.’ Some students are not able to differentiate between chemical knowledge and everyday knowledge and use everyday language to
describe the solution process. Students’ often hold 1 of 4 theories of solutions: 1) Melting theory; 2) Hydrate theory; 3) Chemical Combination theory; and 4) Ionic theory. Students also
tend to believe that the phenomenon of dissolving requires mechanical events to make it happen.
Conceptual Stepping Stones
Middle school students know the characteristics of mixtures, and can differentiate mixtures and pure substances. Students know that the mixture is made up of soluble and insoluble
substances, their distinguishing properties, and can apply these properties to solutions. Students can understand the difference between mixtures and solutions as well as their shared
attributes. Students can understand that a liquid solution consists of two components, the ‘solute’ and ‘solvent’. They can consider reasons why some solvents can dissolve more solutes
while some others can dissolve little or small amount. Students comprehend that heating is a pre-requisite for the melting process, but it not a pre-requisite for the dissolution process.
Students can fundamentally understand differences between physical and chemical change and their features, and can transfer these notions to the dissolution process. They can
comprehend mechanical events that influence the rate of dissolution process. Students understand that temperature and pressure affect the dissolution process and influence amount of
solute in solvent. Students can explain and give examples of how mass is conserved in a closed system.
Early high school students can differentiate between heterogeneous and homogeneous mixtures. They can comprehend that mixtures consist of solutions and the solution is referred to as
homogenous mixture. They can describe and name the structural components and constructs of solutions. Students can distinguish between electrolyte and non-electrolyte solutions based
on the solute but not yet on the ionization of water. Students recognize the impact of water temperature on the ability to dissolve, and can model the difference between melting and
dissolving. Students can represent their understanding of the distinction between chemical reactions of solutions and the dissolution of sodium chloride in water with chemical and ionic
equations, respectively. Students can test the conductivity of various solutions and can represent the process of hydration with ionic equations (symbolically). Students will be able to
comprehend how factors (temperature, stirring, surface area and pressure) affect dissolution/solubility and distinguish what factors increase or decrease dissolution/solubility.
Culminating Scientific Ideas
Later high school students realize that no substance is totally insoluble; there will always be some quantity in solution, however small. Students can differentiate ‘electrolyte’ and ‘nonelectrolyte’ solutions and can categorize electrolyte solutions into ‘weak’ and ‘strong’. Students conceptualize that a solution must have mobile charged ions to conduct electricity. They
can differentiate the following processes: ‘melting,’ ‘hydrate formation,’ ‘chemical combination,’ and ‘dissolving--ion formation.’ They understand dissolution and the nature of the
dissolution processes at three levels, and relate them to the structural components of and constructs. Using a ‘particle model’, students can represent their macroscopic observations with
sub-microscopic or symbolic models (including atomic and molecular models). Students are able to observe visible changes that often accompany reactions. They can symbolically express
chemical formulas and balanced equations for selected reactions. Using ‘kinetic theory’ and particle model students can explain how temperature and pressure affect the process of
dissolution and understand conservation of matter during dissolution process. Students apply and use enthalpy change or hydration enthalpy during the dissolution process and can
therefore decide whether or not a substance can easily dissolve. Students will be able to predict and calculate the amount or direction of the depression of vapor pressure in solutions, the
depression of melting points, and boiling point elevation and relate these properties into everyday examples. Students will know that when a substance freezes, the particles arrange
themselves into an orderly pattern, called a crystal and that the forming of a solution interferes with the orderly arrangement of the particles in the crystal. Also, they can apply their preexisting knowledge of stoichiometry in chemical equations to solubility equilibrium.
Massachusetts Department of Elementary and Secondary Education
Solution Chemistry
44
Solution Chemistry
November 15, 2010
Lower Anchor
Reflective of student concepts
Reconceptualization
Solution Chemistry
Upper Anchor
Reflective of science concepts
CONCEPT & SKILL DETAILS
Initial Ideas42
Before instruction, students often believe
and can:
Pre-instruction
Conceptual Stepping Stones43
Students who view the world in this way believe and can:
Grades 6-8
High school (Early in a course)
Properties of Mixtures and
Solutions
Properties of Mixtures and
Solutions
Culminating Scientific Ideas44
Students who fully understand this topic believe
and can:
High school (Late in a course)
Physical characteristics of solutions
Properties of Mixtures and Solutions45
Possible Misconceptions:
Students sometimes confuse ‘mixtures’
with ‘solutions’. For example, students
believe that ‘solution is a term used for
homogenous and heterogeneous
mixtures’ or ‘solutions are also
heterogeneous mixtures’ (Çalık & Ayas,
2005b).
Students know the characteristics of
mixtures, and can differentiate
mixtures and pure substances.
Students can differentiate between
heterogeneous and homogeneous
mixtures.
Students know that the mixture is
made up of soluble and insoluble
substances.
Students comprehend that mixtures
consist of solutions and the solution is
referred to as homogenous mixture.
Students know the distinguishing
properties of soluble and insoluble
substances.
Students describe the structural
components of solutions (i.e.,
particles, solute, solvent, etc.), and
constructs (i.e., solubility).
Properties of Mixtures and Solutions
Students realize that no substance is totally
insoluble; there will always be some quantity in
solution, however small. For instance, although the
sand on the beach appears insoluble, rain water
dissolves silicon (IV) oxide from rocks and
transports it to the sea.
Students apply the distinguishing
features of soluble and insoluble
substances to solutions.
Students understand the difference
between mixtures and solutions as well
as their shared attributes.
Components of Solution
Possible Misconceptions:
Students are sometimes confused between
the components of a solution. For
example, students believe that water is
the solute and sugar is the solvent
because water breaks the structure of
sugar, decomposes into its own ions (e.g.
Components of Solution
Components of Solution46
Students understand that a liquid
solution consists of two components
(e.g., sugar in water). The components
are ‘solute’ (e.g., sugar) and ‘solvent’
(e.g., water).
When provided with a variety of liquid
solutions students can name the solute
and solvent of each solution.47
Massachusetts Department of Elementary and Secondary Education
Solution Chemistry
45
Solution Chemistry
November 15, 2010
Solution Chemistry
Çalık & Ayas, 2005a), or students believe
sugar and water both may be solute or
solvent-- Sugar and water are both
solvents at the beginning of solution
process and then become solutes (e.g.,
Çalık & Ayas, 2005a).
Differentiating Types of Solutions
Possible Misconceptions:
Students tend to use types of solutions
interchangeably without using the
concept of ‘solubility’. For example, the
solution in Beaker A is dilute; that in
Beaker B is saturated and that in Beaker
C is concentrated (Çalık et al., 2009).
Beaker A and Beaker B are solutions,
Beaker C is a half-solution because in the
cooler water in Beaker C, table salt did
not dissolve completely (Çalık et al.,
2009).
Differentiating Types of Solutions
Differentiating Types of Solutions
Students consider reasons why some
solvents can dissolve more solutes
while some others can dissolve little or
small amount. They can compare
solutions using amount of solute in
equal solvents.
Applying the concept of solubility,
students will be able to distinguish
between ‘dilute and concentrated
solutions’ and “unsaturated, saturated
and supersaturated solutions (e.g.
Çalık & Ayas, 2005; Çalık et al., 2009;
Pınarbaşı & Canpolat, 2003).48
Students’ understanding of
‘dissolution’ enable them to grasp the
concept of ‘solubility’ which is an
important factor in identifying types of
solutions. For example, the solution is
saturated when a specific amount of
water incorporates a maximum amount
of salt that it can dissolve. Solution
which includes less solute than it can
dissolve is an unsaturated solution.
Solution not only contains much more
solute than it can dissolve but also is
heated and then cooled is called a
supersaturated solution (e.g., Çalık et
al., 2009).
Electrolyte and Non-electrolyte
Solutions
Students can distinguish between
electrolyte and non-electrolyte
solutions based on the solute but not
yet on the ionization of water. For
example, students understand that
when sugar dissolves in water, the
solution does not conduct electricity.
Massachusetts Department of Elementary and Secondary Education
Electrolyte and Non-electrolyte Solutions
Using dissolution of ionic or molecular substances
in water, students can differentiate ‘electrolyte’
and ‘non-electrolyte’ solutions. Students
understand that table salt in water conducts
electricity whereas sugar in water or ethyl alcohol
in water does not. Students will categorize
electrolyte solutions into ‘weak’ and ‘strong’
electrolyte solutions using the concept of
Solution Chemistry
46
Solution Chemistry
November 15, 2010
If the solution includes (−1) ion, it can
conduct electricity (e.g., Çalık, 2005).
Solution Chemistry
ionization in water.49
Students conceptualize that a solution must have
mobile charged ions to conduct electricity. The
more ionization increases, the more electric
conductivity increases too. If ionization is very
high, it is called strong electrolyte solutions (i.e.,
HCl, NaCl, H2SO4). If ionization is low, it is called
weak electrolyte solutions (i.e., NH3, acetic acid,
lemon in water, HF). If there is no ionization, it is
named ‘non-electrolyte solution’ (i.e., sugar in
water, ethyl alcohol, CCl4, PCl3, SCl2) (Çalık et
al., 2010).
The Solution Process 50
Possible Misconceptions:
Students identify concepts of solution
with non- or remotely related concepts
(Çalık, Ayas & Ebenezer, 2005). For
example, students use the term melt for
dissolve, and use the concepts of density
and absorption to explain the dissolution
process (e.g., Prieto, Blanco &
Rodriguez, 1989).
Some students are not able to differentiate
between solution chemistry related
chemical knowledge and other chemical
knowledge (Longden et al. 1991).For
example, students refer to the interaction
between the solute and the solvent in the
dissolution process as a chemical change
(Ebenezer and Erickson, 1996; Prieto et
al., 1989).
The Solution Process
Students comprehend that heating is a
pre-requisite for melting process, but it
not a pre-requisite for dissolution
process.
Students fundamentally understand
differences between physical and
chemical change and their features.
Also, they can transfer these notions to
dissolution process.53
Some students are not able to differentiate
between chemical knowledge and
everyday knowledge (Longden et al.
1991) and use everyday language to
describe the solution process (Çalık et al.,
2005; Ebenezer & Erickson, 1996; Prieto
et al., 1989). For example, students use
Massachusetts Department of Elementary and Secondary Education
The Solution Process
Students can understand that
dissolution concept is an integrated
concept in different disciplines and
discriminate it from non-related
concepts such as density, absorption,
chemical change (e.g. Prieto et al.
1989). Thus, they can imagine
‘dissolution process’ accurately in
their mind.
The Solution Process
Students can differentiate the following processes:
‘melting,’ ‘hydrate formation,’ ‘chemical
combination,’ and ‘dissolving--ion formation.’
Students can explain the role and function of
‘solute’ and ‘solvent’ particles and their
interactions.
Students understand dissolution and the nature of
the dissolution processes at three levels
(macroscopic, sub-microscopic and symbolic) and
relate them to the structural components of (i.e.,
particles, solute, solvent, etc) and constructs (i.e.,
solubility).
Using a ‘particle model’, students can represent
their macroscopic observations with submicroscopic or symbolic models (including atomic
and molecular models) (e.g. Kabapınar et al.,
2004).
Solution Chemistry
47
Solution Chemistry
November 15, 2010
Solution Chemistry
the everyday terminology “melt” to
describe the concept of dissolution
(Abraham et al., 1992, 1994; Cosgrove &
Osborne, 1981; Ebenezer and Erickson,
1996; Ebenezer, 2001; Prieto et al.,
1989).
Students’ often hold 1 of 4 theories of
solutions,51 52 listed below, and generally
depict the phenomenon of dissolving at
the macroscopic level (Ebenezer &
Erickson, 1996).
(a) Melting theory
Salt melts, becomes liquid. For example:
"Salt is melting in water and becoming
liquid like water." "Salt became liquid in
the water." "Water molecules are entering
into the salt molecules and making them
liquid."
When solid mixtures of two or more
substances are heated, the terms ‘‘melt’’
and ‘‘dissolve’’ maybe used
interchangeably even though term
‘‘melting’’ is more usual at higher
temperatures (Goodwin, 2002). However,
sodium chloride and its solution in water
include adequate differences to
distinguish the terms ‘‘melting’’ and
‘‘dissolving’’ (Goodwin, 2002).
(b)
(c)
(d) Hydrate Theory
"…And form one kind of chemical thing"
NaC1 + H2O  NaCl.H20 (salty water)
Transitional ideas to address a
melting perspective
Students can interpret and model ice
melting in macroscopic and submicroscopic terms.
Students can interpret and model the
addition of substances to water that
dissolve (for example, sugar, salt,
Kool-Aid crystals) in macroscopic and
sub-microscopic terms.
Students recognize the impact of water
temperature on the ability to dissolve.
Students can model the difference
between melting and dissolving.
Transitional ideas to address a
hydrate perspective
Students can explain the presence of
water of hydration in substances.
Students can symbolically represent
substances with and without water of
hydration.
Massachusetts Department of Elementary and Secondary Education
Formation of Hydrate to Dissolving
Students understand that hydrates are compounds
that incorporate water molecules into their
fundamental solid structure. In a hydrate (which
usually has a specific crystalline form), a defined
number of water molecules are associated with
each formula unit of the primary material. 54
The water in the hydrate (referred to as "water of
hydration") can be removed by heating the
Solution Chemistry
48
Solution Chemistry
November 15, 2010
Solution Chemistry
hydrate. When all hydrating water is removed, the
material is said to be anhydrous (an anhydrate).55
Students know how to measure the percent water
in a hydrate experimentally.
Transitional ideas to address a
chemical combination perspective
Chemical Combination Theory
Salt combines, changes property -- salty
water is new substances by chemical
reaction. For example: "Salt joined with
water nucleus and become invisible."
"Salt mixed and formed a new thing."
"The water shares its molecules with salt
and salt also share its molecules with
water." "Water and salt join together and
they became one category."
Students demonstrate that salt
dissolving in water is a physical
change.
Students distinguish between chemical
reactions of solutions and dissolution
of sodium chloride in water.
Combining Chemically to Dissolving
Students are able to observe visible changes that
often accompany reactions, including evolution of
a gas, formation of a precipitate, color change,
generation or absorption of heat.56
Using a chart on solubility rules and the molecular
formulas for reactants, students can symbolically
express chemical formulas and balanced equations
for selected reactions.
Students represent their understanding
of the distinction between chemical
reactions of solutions and the
dissolution of sodium chloride in
water with chemical and ionic
equations, respectively.
Ionic Theory
Ionic Theory
For example: "Ions are moving in the
water." "Salt dissolves in water and
forms Na ions and Cl ions.”
Students can test the conductivity of
various solutions.
Students represent the process of
hydration with ionic equations
(symbolic).
The Effect of Mechanical Factors on
the Dissolution Process
The Effect of Mechanical Factors
on the Dissolution Process
Students frequently apply the rate of
dissolving of solute (i.e., sugar, table salt)
in solvent (i.e., water) due to mechanical
factors such as shaking, stirring, crushing
(surface area) etc. Students associate
these mechanical factors with the
phenomena of dispersion and dissolution,
Students comprehend that mechanical
events such as shaking/stirring a
solution, and an increase in surface
area of solute (i.e., powdered sugar and
cube sugar), influence rate of
dissolution process and decrease
necessary time for dissolution process.
Massachusetts Department of Elementary and Secondary Education
The Effect of Mechanical Factors
on the Dissolution Process
Ionic Theory
Students understand how to represent the
hydration process symbolically by writing ionic
equation for various liquid-water solutions (such
as sodium chloride in water, or calcium sulfate in
water).
The Effect of Mechanical Factors on the
Dissolution Process
Students will be able to comprehend
how factors (temperature, stirring,
surface area and pressure) affect
dissolution/solubility. Further, they
can distinguish what factors increase
or decrease dissolution/solubility. In
other words, they understand what
Solution Chemistry
49
Solution Chemistry
November 15, 2010
which influence the amount of dissolved
solute in solvent (e.g. Blanco & Prieto,
1997; Çalık, 2005; Çalık et al., 2005,
2009).
Solution Chemistry
factors only speed up dissolution
process and not increase amount of
solute in solvent or solubility.
Mechanical factors only affect the
time necessary for dissolution process
(e.g., Çalık et al., 2009).
Possible Misconception:
Students believe that the phenomenon of
dissolving does not take place without
mechanical events.
Effects of Temperature and Pressure
on Dissolution Process
Effects of Temperature and
Pressure on Dissolution Process
Effects of Temperature and Pressure on
Dissolution Process57
Students are taught the particle model and
‘kinetic theory’ and how temperature and
pressure influence particle motion.
Possible Misconceptions:
However, they have difficulty in applying
these notions to the dissolution process.
For example, students believe that if the
water is very hot, the salt would spread
through the water, but when cooled the
salt would sink again. The salt goes into
solution in a stable form, having been
acted upon by heat; pressing gas particles
liquefies them. Therefore, students’
understanding of the dissolution process
seems difficult; gas particles cannot be
squeezed therefore, the solubility of gas
particles is unchangeable (e.g. Blanco &
Prieto 1997; Çalık et al., 2005, 2007;
Pınarbaşı & Canpolat 2003).
Students understand that temperature
and pressure affect dissolution process
and influence amount of solute in
solvent. For example, students observe
that sugar or table salt in water can
easily dissolve in water when heating.
Further, they comprehend that when
carbonate drink (coca cola) is opened,
bubbles give off.
Using ‘kinetic theory’ and particle model students
can explain how temperature and pressure affect
the process of dissolution based on particle motion
and interactions between solute and solvent
particles (Çalık et al., 2007, 2009). For example, if
pressure increases, interaction between solute and
solvent increases. This means that there is an
increase in solubility. If temperature is enhanced
for a solid into a liquid, its solubility generally
increases due to an increase in particle motion and
interaction between solute and solvent particles.
Conservation of Matter Applied to the
Dissolution Process
Conservation of Matter Applied to the
Dissolution Process
Conservation of Matter Applied to the
Dissolution Process
Conservation of Matter Applied to the Dissolution
Process
Students explain and give examples of
how mass is conserved in a closed
system.
Possible Misconceptions:
Some students think that solute
disappears in solvent and results in a
decrease in solution mass.58
Students understand conservation of matter during
dissolution process, in part based on macroscopic
observations where solutions are colorful as a
result of colorful solute (Taylor and Coll, 1997;
Stavy, 1991).
Students may believe that solution
mass is heavier or smaller than total
Massachusetts Department of Elementary and Secondary Education
Solution Chemistry
50
Solution Chemistry
November 15, 2010
Solution Chemistry
mass of solute and solvent (e.g.,
Driver & Russell, 1982; Holding,
1987; Johnson & Scott, 1991).
Energy Changes that Occur during
Dissolution
Interactive Effects
Colligative Properties of Nonvolatile
Solute-Solutions
Energy Changes that Occur during
Dissolution
Energy Changes that Occur during
Dissolution
Possible Misconceptions:
Students typically have been taught
chemical bonding and intermolecular
forces but they have difficulty in
linking these concepts with enthalpy
change or hydration enthalpy during
the dissolution process (e.g. Çalık et
al., 2005; Ebenezer & Fraser, 2001).
That is, they may think energy is
involved in solution process as (i) you
give energy; (ii) water gives energy;
(iii) salt gives energy; (iv) reaction
gives off energy (e.g., Ebenezer &
Fraser, 2001).
Students can reason about why some
solutes, (i.e. Sugar, Table Salt etc.)
dissolve in solvents (i.e. water)
rapidly, the other do slowly (i.e.
AgCl).
Interactive Effects
Interactive Effects
Energy Changes that Occur during
Dissolution
Students apply and use enthalpy change or
hydration enthalpy during the dissolution process
based on their understandings of chemical bonding
and intermolecular forces (e.g., Çalık et al., 2005;
Ebenezer & Fraser, 2001). Hence, they can decide
whether or not a substance can easily dissolve.
The energy change or hydration
enthalpy may be used to determine
whether or not ionic substances
dissolve in water. In other words,
students can address how an ionic
substance easily dissolves as a result
of hydration enthalpy.59
Interactive Effects
Colligative Properties of
Nonvolatile Solute-Solutions60
Colligative Properties of
Nonvolatile Solute-Solutions61
Colligative Properties of Nonvolatile SoluteSolutions
Students recognize that a substance has
a melting point and a boiling point,
both of which are independent of the
amount of the sample.
Physical properties are determined by
the concentration of dissolved particles
in a mixture, and affected by the type
of dissolved particles. Osmotic
pressure (tendency of water to flow
from high water concentration to low
water concentration), boiling point
elevation and freezing point
depression are examples of colligative
properties. The greater the particle
concentration, the stronger the
colligative effect.62
Students will be able to predict and calculate
amount or direction of the depression of vapor
pressure in solutions, the depression of melting
points, and boiling point elevation and relate these
properties into everyday examples such as
spreading salt on icy road (Çalık, 2005, 2008;
Pınarbaşı & Canpolat 2003).
Possible Misconceptions:
tudents may consider that freezing and
boiling points of salt dissolved in
water are not different from those of
water because salt dissolved in water is
a liquid like water (Çalık, 2005, 2008).
Massachusetts Department of Elementary and Secondary Education
Students know the following conceptual ideas:
When a substance freezes, the particles arrange
themselves into an orderly pattern, called a crystal.
The forming of a solution (such as when salt is
added to water or ice) interferes with the orderly
arrangement of the particles in the crystal.
Therefore, more kinetic energy (heat) must be
Solution Chemistry
51
Solution Chemistry
November 15, 2010
Solution Chemistry
removed from the solvent (i.e., water) for freezing
to occur. This results in a lower freezing point.
Furthermore, the more particles of solute (i.e., salt)
added, the more kinetic energy must be removed.
Solubility Equilibrium65 66
Solubility Equilibrium
Possible Misconceptions:
Students may believe that there is no
precipitation and dissolution at
equilibrium or dissolution stops at
equilibrium (Önder & Geban, 2006;
Raviolo, 2001).
Students can write down chemical
equations and determine coefficients
in solubility equilibrium.
The greater the concentration of solute, the lower
the freezing point of the solvent. 63 The more
particles there are, the greater the disruption and
the greater the impact on particle-dependent
properties (colligative properties) like freezing
point depression, boiling point elevation, and
osmotic pressure.64
Solubility Equilibrium
Students can comprehend ‘solubility equilibrium’
and its dynamic structure at sub-microscopic level
by help of the terms’ balance’, ‘particle model’,
‘ionic compound’ and ‘equilibrium’. Also, they
can apply their pre-existing knowledge of
stoichiometry in chemical equations to solubility
equilibrium.
Students not only capture description of ‘solubility
equilibrium’ but also understand that the solubility
equilibrium is a dynamic procedure at submicroscopic level. That is, in dissolution of
potassium nitrate in water,
KNO3(s)
K+ (aq) + NO3- (aq)
the number of potassium and nitrate ions
producing potassium nitrate is equal to that of
dissolution of potassium nitrate.
Grades
Pre-instruction
Grades 6-8
High school (Early in a course)
Key Vocabulary
Substance, mixture, (in-) soluble,
Homogeneous, heterogeneous, solute,
solution, components,
solvent, solubility, (un-, super-)
dissolve/dissolution, pure substance,
saturated, dilute, concentrated, (non-)
property, liquid, melt, mechanical
electrolyte, melt, ion (-ic, -ization),
event, closed system.
hydration, equilibrium, chemical
equation/reaction, electricity, enthalpy
Massachusetts Department of Elementary and Secondary Education
High school (Late in a course)
Molecular, macroscopic, sub-microscopic,
symbolic, anhydr (-ous /-ate), kinetic theory,
enthalpy, IMF, freezing point, precipitate, vapor
pressure, depression, intermolecular forces.
Solution Chemistry
52
Solution Chemistry
November 15, 2010
Solution Chemistry
Authors and Reviewers:
Dr. Jazlin Ebenezer, Wayne State University, Michigan (contributor)
Dr. Muammer Çalık, Karadeniz Technical University, Trabzon, Turkey (contributor)
Dr. Hannah Sevian, University of Massachusetts, Boston, Massachusetts (reviewer and contributor)
References
Abraham, M. R., Gryzybowski, E. B., Renner, J. W., & Marek, A. E. (1992). Understanding and misunderstanding of eighth graders of five chemistry concepts found in textbooks.
Journal of Research in Science Teaching 29: 105–120.
Abraham, M. R., Williamson, V. M., & Westbrook, S. L. (1994). A cross-age study of the understanding five concepts. Journal of Research in Science Teaching 31: 147–165.
Blanco A. & Prieto, T. (1997). Pupils’ views on how stirring and temperature affect the dissolution of a solid in a liquid: A cross-age study (12 to 18). International Journal of
Science Education, 19:303–315.
Cosgrove, M., & Osborne, R. (1981). Physical Change (Working Paper No. 26), Learning in Science Project, University of Waikato, Hamilton, New Zealand.
Çalık, M. & Ayas, A. (2005a). A Comparison of level of understanding of grade 8 students and science student teachers related to selected chemistry concepts. Journal of Research
in Science Teaching, 42(6), 638-667.
Çalık, M. & Ayas, A. (2005b). “A Cross-Age Study on The Understanding of Chemical Solution and their Components”, International Education Journal, 6(1), 30-41
Çalık, M., Ayas, A. & Coll, R.K. (2010). Investigating the effectiveness of usage of different methods embedded with four-step constructivist teaching strategy. Journal of Science
Education and Technology, 19(1):32–48.
Çalık, M., Ayas, A. & Coll, R.K. (2009). Investigating the effectiveness of an analogy activity in improving students’ conceptual change for solution chemistry concepts.
International Journal of Science & Mathematics Education, 7(4), 651-676.
Çalık, M. (2005). A cross-age study of different perspectives in solution chemistry from junior to senior high school. International Journal of Science and Mathematics Education,
3, 671–696.
Çalık, M., Ayas, A. & Coll, R.K. (2007). Enhancing pre-service primary teachers’ conceptual understanding of solution chemistry with conceptual change text. International
Journal of Science and Mathematics Education, 5(1), 1-28.
Çalık, M., Ayas, A. & Ebenezer, J.V. (2009). Analogical reasoning for understanding solution rates: students’ conceptual change and chemical explanations. Research in Science
& Technological Education, 27(3), 283-308.
Çalık, M., Ayas, A. & Ebenezer, J.V. (2005). A review of solution chemistry studies: insights into students’ conceptions. Journal of Science Education and Technology, 14(1), 2950.
Çalık, M. (2008). Facilitating students’ conceptual understanding of boiling using a four-step constructivist teaching method. Research in Science & Technological Education,
26(1), 59-74.
Drıver, R., & Russell, T. (1982). An investigation of the ideas of heat temperature and change of state of children aged between 8 and 14 years, Unpublished Paper, University of
Leeds.
Duschl, R. A.; Schweingruber, H. A.; Shouse, A., Taking science to school: Learning and teaching science in grades K-8. National Academy Press: Washington, D.C., 2007.
Ebenezer, J.V. (2010). Citation not provided.
Ebenezer J.V. & Erickson, L.G. (1996). Chemistry students’ conception of solubility: a phenomenograpy. Science Education, 80:181–201.
Ebenezer, J. (2001). A hypermedia environment to explore and negotiate students’ conceptions: Animation of the solution process of table salt. Journal of Science Education and
Technology, 10: 73–91.
Ebenezer, J. V., & Fraser, M.D. (2001). First year chemical engineering students’ conception of energy in solution processes: Phenomenographic categories for common
knowledge construction, Science Education 85: 509–535.
Fortman, J.J. (1994). Solutions and electrolytes. Journal of Chemical Education, 71(1):27–28.
Goodwin, A. (2002). Is salt melting when it dissolves in water? Journal of Chemical Education 79: 393–396.
Holding, B. (1987). Investigation of school children’s understandings of the process of dissolving with special reference to the conservation of matter and the development of
atomistic ideas, Unpublished PhD thesis, University of Leeds.
Massachusetts Department of Elementary and Secondary Education
Solution Chemistry
53
Solution Chemistry
November 15, 2010
Solution Chemistry
Johnson, K., & Scott, P. (1991). Diagnostic teaching in the science classroom: Teaching/learning strategies to promote development in understanding about conservation of mass
on dissolving. Research in Science and Technological Education, 9(2): :193–212.
Kabapınar, F., Leach, J., & Scott, P. (2004). The design and evaluation of a teaching–learning sequence addressing the solubility concept with Turkish secondary school students.
International Journal of Science Education 26: 635–652.
Longden, K., Black, P., & Solomon, J. (1991). Children’s interpretation of dissolving. International Journal of Science Education, 13: 59–68.
Ogborn, J., Kress, G., Martins, I. and McGillicuddy, K. Explaining science in the classroom. Open University Press: Buckingham, UK, 1996.
Önder, İ. & Geban, Ö. (2006). The effect of conceptual change texts oriented instruction on students’ understanding of the solubility equilibrium concept. Hacettepe University
Journal of Education, 30, 166-173.
Pınarbaşı, T., & Canpolat, N. (2003). Students’ understanding of solution chemistry concepts. Journal of Chemical Education, 80: 1328–1332.
Prieto, T., Blanco, A. & Rodriguez, A. (1989) The ideas of 11 to 14-year old students about the nature of solutions. International Journal of Science Education, 11: 451–463.
Raviolo, A. (2001). Assessing students’ conceptual understanding of solubility equilibrium. Journal of Chemical Education, 78(5), 629-631.
She, H.C. (2004). Facilitating changes in ninth grade students’ understanding of dissolution and diffusion through dslm instruction. Research in Science Education, 34, 503-525.
Smith, C. L., Wiser, M., Anderson, C. W., and Krajcik, J. (2006). Measurement: Interdisciplinary Research and Perspectives, 4 (1&2), 1-98.
Smith, J. P., diSessa, A. A., and Roschelle, J. (1993). Misconceptions reconceived: A constructivist analysis of knowledge in transition. Journal of the Learning Sciences, 3(2),
115-163.
Stains, M., Escriu-Sune, M., Molina Alvarez, M. L., & Sevian, H. (Submitted). Assessing Secondary and College Students’ Understanding of the Particulate Nature of Matter:
Development and Validation of the Structure and Motion of Matter (SAMM) Survey.
Stavy, R. (1991). Using Analogy to overcome misconceptions about conservation of matter. Journal of Research in Science Teaching, 28(4), 305-313.
Talanquer, V. (2009). On cognitive constraints and learning progressions: The case of structure of matter. International Journal of Science Education, 31(15), 2123-2136.
Taylor, N. & Coll, R. (1997). The use of analogy in the teaching of solubility to pre-service primary teachers. Australian Science Teachers’ Journal 43: 58–64.
Notes:
42
There are many solution chemistry papers and reviews of insight into students’ conceptions (Çalık et al., 2005), including research on alternative conceptions, many of which
occur after students have some initial exposure to concepts in solution chemistry.
43
There is limited empirical evidence that suggests which intermediate ideas are productive stepping stones. We have, however, evidence that students can develop these ideas
(citations noted). Also, these intermediate understandings address ideas for which we have some informed hypotheses that lead to the important ideas in the targeted
understanding. In many cases to move from an intermediate understanding to the targeted level of understanding, all connections between ideas need to be consistently made.
44
The core and integrated concepts are represented in the storyline. These need to be connected in order to develop a conceptual network.
45
The biggest obstacle for students in traditional chemistry courses is the vocabulary, particularly for students with limited English proficiency. For example, high school students
do not need to learn the difference between homogeneous and heterogeneous mixtures. There is no need for students to be able to distinguish that solutions are homogeneous
mixtures, and that heterogeneous mixtures are not solutions. This is macroscopic thinking that is descriptive and is not particularly useful at the microscopic level, which is
where the vanguard of chemistry operates today.
46
Students’ understanding may be changed from their initial conceptions into scientific ideas using proportions of solvent and solute and the phase of solution (solid, liquid, or gas)
which depends on that of the solvent.
47
Students should be introduced to other types of solutions such as gas in gas (i.e., composition of air, mixture of gases), liquid (e.g., ethanol) in liquid (e.g., water); and solid
(e.g., copper) in solid (e.g., gold) such as in jewelry.
48
The conscious use of proper terms for the types of solutions will help students not to use the foregoing terms interchangeably.
49
Fortman’s (1994) analogies can be used to help students’ understand ionic crystal, molecular structure and ionization (e.g., Çalık, 2005) and then use this understanding to
determine electrolyte and non-electrolyte solutions. In fact, for re-conceptualization, students can be shown that drinking water conducts electricity. This will demonstrate the
evidence of the presence of dissolved salts in drinking water.
Massachusetts Department of Elementary and Secondary Education
Solution Chemistry
54
Solution Chemistry
November 15, 2010
Solution Chemistry
Students are likely to have learned the ‘particle model’ but they do not readily call upon this knowledge to apply to chemical processes. Even if they did, the applications are
often incorrect. Students readily pay more attention to macroscopic observations and this deters them from linking the chemical processes to the sub-microscopic or symbolic
knowledge (e.g., Ebenezer & Erickson, 1996; Holding, 1997; Prieto et al., 1989).
51
Students and Chemists’ Parallel Conceptions
 Students’ conceptions of solutions parallel the historical development of solution chemistry (i.e., chemists’ early views of ‘solution chemistry’) (e.g., Ebenezer,
unpublished—see table below)— thermo-chemical theories—melting theory and hydrate theory; chemical combination theory; and ionic theory. This is because students
attempt to explain the macroscopic event (salt/sugar dissolving in water) based on their observations and what they have previously learned in chemistry. That is, students
depict the phenomenon of dissolving at the macroscopic level.
 Show the chart on students’ and chemists’ parallel conceptions to emphasize that students’ conceptions parallels the early chemists’ conceptions and the importance of
studying chemical knowledge development from a historical perspective. Early chemists explored and tested their ideas through experimentation, and made evidenceexplanation connections for experimental validity. They also shared their ideas for critical inquiry and validation. Throughout the development of chemical knowledge,
consensus/dissensus was reached through a social process. This process is known as social objectivity. The point is exposition of one’s ideas, consideration of multiple
ideas (intra-variations and inter-variations) is one of strength and not a sign of weakness. Teaching from nature of science point of view, teachers have an opportunity to
show intellectual empathy to students’ ideas. Students’ ideas then are used as curriculum theoretical frameworks for validation of knowledge through experimentation
(testing) and argumentation (making evidence- explanation connections).
 Students should compare their early conceptions with the historical development of solution chemistry so that they understand the nature of science. They should feel that
there is strength in exploring and exposing their multiple conceptions and subject them for testing, look for evidence, make evidence-explanation connections, and allow
for consensus toward theory building.
Table: Relationship between Scientific Ideas and Students' Conceptions
Scientific Ideas
Teacher-Made Categories & Students’ Expressions
For Fourcroy, dissolution process involved the participation (union) of the solvent (dissolvant) Thermochemical Theory
and solute (dissolvence), a solid melting in a liquid and partaking of its liquidity (Partington,
Salt is melting (Liquefaction or melting theory)
1970, p. 641).
"Water molecules are entering into the salt molecules and making them liquid."
50
Mendeleev's hydrate theory developed since 1865 to explain the properties or nature of
solutions. He believed in the existence of discontinuities between solutes and solvents. He
attributed the formation of different hydrate compounds at different temperatures to the
anomalies of freezing points and colligative properties
Hermann Boerhaave (1668-1738) "believed that chemical reaction essentially the same as
solution. The solvent, or menstruum, usually a liquid, was composed of fine particles that
pushed their way between the particles of dissolved substance. The atoms of each then
remained suspended and related to one another as required by the affinities of each substance
for the other" (Leicester, 1956,p. 124).
Salt attaches to water (hydrate theory)
"Salt is reacting with water and forming salty water."
"…And form one kind of chemical thing"
NaCl.H20 Salt water
Salt forms a new substance with water.
(chemical combination theory)
"When salt is added to water it dissolves in water—For example, if NaCI and
water is mixed NaOH is created and H2 is evaporated. In dissolving atoms get
separated from the orbit. Atoms are running away from their shell and joining
and making a new shell."
Berthollet also considered that "there was no fundamental difference between solution and
chemical combination" (Leicester, 1956,p. 152).
Massachusetts Department of Elementary and Secondary Education
Solution Chemistry
55
Solution Chemistry
November 15, 2010
Arrehenius proposed that certain substances dissolved in water because of their electrical
properties (Brock, 1992, p. 370). Arhenius came to the conclusion that the active molecules
were ions, the charged particles. This meant that ionic potassium in potassium chloride is
different from atomic potassium, and would not dramatically react with solvent water.
Solution Chemistry
Ionic theory
"Ions are moving in the water." "Salt dissolves in water and forms Na ions and
Cl ions.”
Ionic theory also explained Hittorf's and Kohlrausch's results: The properties of a salt are the
sum of the properties of the ions."
Faraday and Volta's work on electricity also helped to prove ionization as a mechanism.
52
The distinction between the macroscopic and description-based differentiation between chemical and physical properties/changes is often meaningless. It does not make sense to
teach students definitions that break down and which they will need to un-learn later if they progress in studying chemistry. The progression of four theories (melting, hydrate,
chemical combination, ionic) in historical context could be useful, primarily because the story nature of history helps students remember how thinking progresses toward more
sophisticated understanding, and it can therefore help them integrate more sophisticated ways of thinking into their own understanding. Research supports the claim that students
tend to learn science more effectively if they understand science as a story, with a protagonist, climax, resolution, and moral.
53
When students, grade 6 through graduate school, think about mixtures, they focus first (fixate) on the solute (the less plentiful component), and initially think of the solvent (more
plentiful component) as continuous while the solute is particulate. Later, as conceptual understanding deepens, students' thinking about the more plentiful component of the
mixture progresses through stages of understanding. The words solute, solvent, and solution are meaningful to bench chemists, but confusing to students. Furthermore, these
terms again reflect descriptive and macroscopic chemistry. These terms do not always have meaning at the vanguard of chemistry, where it can be irrelevant which component is
the solute and which is the solvent. Since there are crucial concepts that students must understand that rely on differences between the components of mixtures, one can borrow
the conventions of algebra and call the components A and B (or X and Y). This would help further students' abilities to connect abstractions in math (that variables stand for
something) with chemistry.
54
Gypsum is a hydrate with two water molecules present for every formula unit of CaSO4. The chemical formula for gypsum is CaSO4 • 2H2O and the chemical name is calcium
sulfate dihydrate. Note that the dot in the formula (or multiplication sign) indicates that the waters are there. Other examples of hydrates are: lithium perchlorate trihydrate LiClO4 • 3H2O; magnesium carbonate pentahydrate - MgCO3 • 5H2O; and copper(II) sulfate pentahydrate - CuSO4• 5 H2O.
55
CuSO4• 5 H2O(s) (hydrate) + HEAT ---> CuSO4(s) (anhydrate) + 5H2O(g)
56
Changes that are common observed include:
 Evolution of a gas. When one of the products of a reaction is a gas, bubbles of the gas may appear in the solution or on the surface of a solid. When a gas is produced,
foam may form, or if the gas evolution is rapid enough a "fizzing" sound may be heard.
 The formation (or disappearance) of an insoluble solid called a precipitate. Some reactions result with the production of an insoluble solid called a precipitate, which
normally settles to the bottom of the reaction mixture as a collection of particles. Describing a precipitate involves not only noting its color but also texture. Precipitates
can exist in the form of crystals, gelatinous or milky suspensions, or granular solids. The disappearance of a solid can also indicate a reaction has taken place.
 A color change. Both precipitation reactions and redox reactions can involve color change. Also, color change can be associated with reactions that result in the
formation of a species referred to as a complex ion.

Evolution or absorption of heat. Energy is transferred in all reactions. Sometimes the vessel in which the reaction occurs may get warm or cold, depending on whether the
reaction evolves or absorbs heat.
57
The effects of temperature and pressure on particle motion during the dissolution process can be studied using the activities noted by Çalık et al. (2007, 2009).
58
Students may reconcile their conceptions of conservation of matter and the dissolution process with the help of activities reported by Taylor and Coll (1997) and Stavy (1991).
59
Enthalpy change or hydration enthalpy during dissolution process may be understood by means of students’ pre-existing knowledge of chemical bonding and intermolecular
forces (e.g. Çalık et al., 2005; Ebenezer & Fraser, 2001) can be used to reconcile students’ early conceptions--(i) you give energy; (ii) water gives energy; (iii) salt gives energy;
(iv) reaction gives off energy (e.g., Ebenezer & Fraser, 2001).
Massachusetts Department of Elementary and Secondary Education
Solution Chemistry
56
Solution Chemistry
November 15, 2010
Solution Chemistry
Students’ initial beliefs may result from students’ conceptions of solutions and it components.
Understanding student views of solution and its components can be applied to colligative properties in which solution contains a nonvolatile solute.
62
Ice cream, a mixture of milk, sugar and vanilla, is really an aqueous mixture with many particles in each liter. Because of this the freezing point of ice cream is lower that that of
water, so to freeze ice cream, or to keep it frozen, you must keep its temperature significantly below 0 degrees Celsius. Adding rock salt to ice produces a melting ice and
saltwater mixture with a depressed freezing point in which the ice cream can be frozen.
63
When sodium chloride is placed on the highway or on steps, the freezing point is lowered and the ice melts. Elective or advanced concept: Sodium chloride is used for three
reasons. First, some solids such as sugar do not dissolve in ice water as well as salt. Second, salt is an abundant mineral in the form Halite and is not expensive. Finally, when
sodium chloride dissolves, it separates into two particles (Na+ and Cl-), lowering the freezing point further. It is called ionic dissociation.
64
Ice has to absorb energy in order to melt, changing the phase of water from a solid to a liquid. When you use ice to cool the ingredients for ice cream, the energy is absorbed
from the ingredients and from the outside environment (like your hands, if you are holding the baggie of ice!). When you add salt to the ice, it lowers the freezing point of the
ice, so even more energy has to be absorbed from the environment in order for the ice to melt. This makes the ice colder than it was before, which is how your ice cream freezes.
Ideally, you would make your ice cream using 'ice cream salt', which is just salt sold as large crystals instead of the small crystals you see in table salt. The larger crystals take
more time to dissolve in the water around the ice, which allows for even cooling of the ice cream. You could use other types of salt instead of sodium chloride, but you couldn't
substitute sugar for the salt because (a) sugar doesn't dissolve well in cold water and (b) sugar doesn't dissolve into multiple particles, like an ionic material such as salt.
Compounds that break into two pieces upon dissolving, like NaCl breaks into Na+ and Cl-, are better at lowering the freezing point than substances that don't separate into
particles because the added particles disrupt the ability of the water to form crystalline ice. The salt causes the ice to absorb more energy from the environment (becoming
colder), so although it lowers the point at which water will re-freeze into ice, you can't add salt to very cold ice and expect it to freeze your ice cream or de-ice a snowy sidewalk
(water has to be present!). This is why NaCl isn't used to de-ice sidewalks in areas that are very cold. When 1 mole of NaCl dissolves in a liter of water it dissociates into 1 mole
of sodium ions and 1 mole of chloride ions, or a total of 2 moles of particles per liter of mixture (a 2M concentration). When 1 mole of sugar dissolves in a liter of water there
are just 1 mole of sugar molecules per liter (a 1M concentration).
65
Possible additional topics for advanced study include:
 Meanings and Functions of Ksp
 Effects of Mechanics, Temperature, Concentration, and Pressure on Solubility Equilibrium
66
The main conceptual idea students should learn about equilibrium is that many reactions do not go entirely from reactants to products, but rather, the reaction ceases to progress
noticeably at some point. The key is the word "noticeably," because within this lies dynamic equilibrium. Students cannot reach this understanding until they are able to achieve
a conceptual level of understanding about particles being in constant motion. This is the highest level of understanding in Talanquer's dynamics dimension, and thus it is no
surprise that many students have difficulty with the concept of dynamic equilibrium.
60
61
Massachusetts Department of Elementary and Secondary Education
Solution Chemistry
57