In the Classroom
Terra Firma: “Physics First” for Teaching Chemistry to Pre-Service Elementary School Teachers Michelle B. More Department of Chemistry, Weber State University, Ogden, UT 84408;
[email protected] In a society where even children play with high-technology toys that most of their parents cannot understand, let alone master, scientific literacy for all members of society, including children and adolescents, is of utmost importance (1, 2). A previous editor of this Journal has suggested that scientific illiteracy in America arises from students receiving insufficient science exposure during their elementary school years (3). Others have noted that this lack of science coverage is easily accounted for by elementary teachers’ own fears of science that result from a lack of appropriate, if any, science education (4). Activities have been initiated to bring science to elementary schools via special science programs that increase students’ exposure to chemistry (5–8). However, it has been noted that the most desirable approach is to provide science education and training to elementary school teachers (9, 10). Several innovative pre- and in-service elementary teacher chemistry (9, 11) and integrated science (12, 13) classes have been noted in this Journal. This paper describes a pre-service elementary school teacher chemistry class that differs from previous courses by incorporating the “physics first” idea popularized by Leon Lederman (14, 15). In this class, the conventional sequence of biology, chemistry, and physics (16) has been reversed and truncated; only basics physics followed by introductory chemistry is taught. Though as of this date there have been no formal studies of the physics-first approach, anecdotal information indicates that both science literacy and science interest increase using this method (17, 18). How the Physics-First Curriculum Creates the Foundation for Teaching Chemistry The support for a “physics-first” approach for introductory and pre-service elementary school teacher chemistry classes rests on several researched ideas from the last 35 years. Some of these key ideas are: 1. Students construct understanding (19, 20) 2. Explaining new concepts by referring to related concepts that are not well understood by students often results in little or no understanding (21–23) 3. New information must be linked to old information to be understood (24, 25) 4. Many students come to college with poorly developed formal reasoning skills (26, 27)
As explained in the following paragraphs, the physicsfirst approach makes it possible to incorporate these key findings in teaching introductory chemistry to pre-service elementary teachers and others.
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Physics is identified as the foundational science and provides the terra firma (solid ground) for chemistry, the central science (18). Most pre-service elementary teachers have little or no physics background. To construct an understanding of chemistry, it is logical that these students first learn basic physics concepts to serve as building blocks (18). For example, an understanding of atomic and nuclear structure, the bonding of atoms to form molecules, and the deflection of a beam of β and α particles from charged plates (a figure often shown in introductory texts) requires knowledge of electrostatic forces of repulsion and attraction, and the strong nuclear force. Simply referring in a piecemeal fashion to physics concepts that are not familiar to students does not provide an opportunity for students to build on what they already know and have fully assimilated, often resulting in little real understanding. By teaching basic physics first, a student is introduced to the toolbox of natural laws that govern the universe, matter, and energy. Teaching chemistry after physics gives students the opportunity to construct a view of chemistry using tools they have already mastered, thus reinforcing the physics, and making a link from already learned concepts (physics) to new concepts (chemistry). The physics-first approach also provides more continuity than introducing the physics bitby-bit, as needed, before the chemistry topic requiring it. This physics-first practice is not as challenging to students’ limited experience with scientific reasoning. Numerous concrete examples found in the introductory physics curriculum lend themselves to demonstrations that students can experience sensorially on a macroscopic level. For example, students can experience the repulsion of like electrical charges using two charged balloons, and the attraction of oppositely charged objects such as a wool sweater and a balloon that have been rubbed together. Such demonstrations can be referred to later when discussing how polar or ionic solutes dissolve in aqueous solutions. The importance of prior experience with concrete examples comes indirectly from studies using Piaget’s cognitive development theory (28–39). Studies indicate that up to 50% of college students function at the concrete-operational stage of cognitive development. In Piaget’s scheme, this stage precedes the formal operational stage that is necessary for learning much of chemistry (30, 35, 40). Research shows that both concrete and formal thinkers profit from learning with concrete examples (41, 42). Class Organization and Teaching This semester-long class consists of approximately two weeks of an introduction to science, five weeks of physics, and six weeks of chemistry. Each week the class is divided
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In the Classroom
Table 1. Distribution of Lecture Topics and In-Class Activities Lecture Topics
Relevant In-Class Activities
1
Nature of science: What is studied, how is it studied, the scientific method, observations based on the senses and their limitations
Observing a magnetic pendulum; viewing 2D optical illusions; comparison and contrast of science and pseudoscience
2
Measurement: The need for measurement systems, measurement systems and standards, and their origins
Muscle memory and mass; constructing a water clock (clepsydra)
3
Classification
Binary classification of students’ shoes
4
Experimentation: Experimental design, characteristics of good experiments
Rolling balls down a V-shaped ramp activity
5
Representing data: Relative magnitudes, graphing protocol
Graphing data from the rolling balls activity (above)
6
Motion: Force, speed, velocity, acceleration, planetary motion, weight/mass, gravity
Acceleration of toy cars using penny roll weights as forces
7
Newton’s laws of motion
Inertia and free-falling objects demonstrations; water rockets
8
Energy and work: Simple machines, mechanical advantage, forms of energy, conservation of energy, energy conversions
First- and second-class levers; ramps; pendulums; rubbing hands (energy of friction)
9
Heat and temperature: Heat flow, conduction, convection, radiation, temperature scales, thermometers
Stretching rubber bands; food color drops in hot and cold water
10
Electricity and magnetism: Static electricity, electrons, atomic nuclei, molecular polarity, batteries, current electricity, circuits, magnets, magnetic poles, magnetic fields, Earth’s magnetic field
Charged objects (balloons) and static electricity; disassembling a light bulb; making a light bulb light with a battery and aluminum foil; student penny circuit; homing pigeon activity (with compass)
11
Light: Light waves, electromagnetic nature of light, speed of light, electromagnetic spectrum, reflection and refraction, mirrors, lenses, pinhole camera
Student and rope waves; playing with double convex lens; playing with mirrors and keychain lasers
12
What is the study of chemistry?
Samples of natural and manufactured items
13
Matter: Pure substances and mixtures, how matter is arranged in nature
Gummi bear–toothpick molecules and their chemical formulas
14
Periodic table: Elements, elemental symbols, compounds, formulas, distribution of elements in human body (animals), plants, Earth, the universe, items in daily life
Lego reactions; physical and chemical changes demonstrations from everyday life
15
Physical and chemical properties; physical and chemical changes; changes of state
Student-made atomic models
16
Atomic structure: Nuclear model, subatomic particles’ masses and charges, isotopes, atomic weight
Ionic compound musical chairs
17
Chemical bonds: Ionic and covalent, characteristics of each type of compound
Vinegar and baking soda experiments
18
Chemical reactions: Nomenclature, the law of conservation of matter, rates of chemical reactions, catalysts
Catalyst activity: Effect of alcohol, heat, cold, and acid on catalase in potatoes
19
Solutions: Solvent and solutes, dissolving (how and why), miscible and immiscible solutes, properties of ionic and covalent solutes
Conductivity apparatus with unknown solutes in aqueous solution
20
Soaps and detergents: Micelles, effects of hard water
Effects of hard water on soaps and detergents demonstration
21
Acids and bases: Characteristics of acids and bases, pH scale, indicators, acids and bases in daily life
Colorful acid-base indicators; demonstrations of acid and base reactions with everyday materials
22
Polymers: Natural (cellulose, silk, starch, wool, rubber, proteins, carbohydrates) and synthetic (polyethylene, polystyrene, PVC, teflon, orlon, nylon, PET)
Student polymer chain with cross-linking; recycling codes on plastics
23
Radioactivity: Types of radiation, sources of radiation, half-life, fission and fusion, effects of radiation on humans
Geiger counter; play-doh (or clay) nuclei for fission and fusion
into approximately 2.5 hours of lecture and in-class activities, and 2.5 hours of laboratory activities. Table 1 contains the topics covered in the class as well as associated in-class activities and demonstrations. The topics in Table 1 lend www.JCE.DivCHED.org
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themselves to conceptual learning with little or no mathematics used. The in-class activities and demonstrations emphasize the concrete, often easy-to-experience nature of physical science.
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Table 2. Distribution of Laboratory Topics and Their Associated Activities Related Lecture Topics
Laboratory Topic
1, 2
Measurements and calculations I
Measure 2D objects; calculate perimeters and area
1, 2
Measurements and calculations II
Measure 3D objects; calculate surface area and volume
Experimentation; variables and graphs
Study simple and compound pendulum and graph behavior
Simple machines and mechanical advantage
Construct and experiment with levers, pulleys, ramps, and screws
Energy and work
Mix liquid samples at different temperatures; study the heat of fusion of ice; investigate evaporative cooling; construct water wheels
10
Static electricity and mystery circuits
Build a cellophane-tape electroscope and create circuits
10
Current electricity and magnetism
Make a compass and study its behavior near current electricity; build an electric motor
11
Light, lenses, and mirrors
Make and study lenses made of bottles and Knox-Blox gelatin, using key-chain lasers as light sources
Physical and chemical properties and changes
Investigate household physical and chemical changes; black ink paper chromatography; starch–iodine reactions in food and household items
19
Mixtures and solutions
Investigate dissolving of candy in several solvents; make fizzy lemon soda
21
Behavior of acids and bases
Investigate the acid–base properties of household items using natural vegetable and fruit acid–base indicators
22
Introduction to the chemistry of polymers
Make slime by cross-linking polyvinyl alcohol and white glue; study the properties of LDPE, HDPE, and sodium polyacrylate in baby diapers
Any
Development of a laboratory activity
Create own activities for classmates to do
Any
Development of a laboratory activity
Do their own and peers' activities; critically evaluate activities they do
1, 2, 4, 5 8 8, 9
12, 13, 15
List 1. Assessment Tools and Their Relative Contributions to a Final Course Grade
Assessment Tool
Weighting
Physics and chemistry homework (4) Lab write-ups (13) Physics exams (2) Chemistry exam (1)
20% 20% 40% 20%
Table 2 contains the laboratory activities and their content. The laboratory activities are designed either to be done by elementary students, or in a few cases, demonstrated by the teacher. No textbook is used in this course. Instead, the students have Internet access to the course Web site that contains a comprehensive set of classroom notes, worksheets, and handouts, and laboratory activities. All written materials used in the class are available by request from the author. The introduction and physics portions of the class are currently taught by a Ph.D. astrophysicist who is also a trained and certified secondary education teacher. The chemistry portion is taught by the author, a Ph.D. physical chemist. Both instructors are present in the class and the laboratory during all sessions. Though neither instructor has taught the entire class alone, both are qualified and capable of doing so. The class has been taught 12 times over the past 11 years.
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Student Assessment and Reaction to the Class The assessments used in the class and their weighting are shown in List 1. Homework assignments are designed to help the students review and use recently learned material. Most of the homework exercises could be used with the pre-service teachers’ future students with little or no modification. Lab write-ups consist of two parts: (i) analysis of student data with probing questions for students about relationships in the data, and (ii) student suggestions about similar activities that could be used in an elementary school setting. It is emphasized in lab that students are not graded on whether or not their analysis of data is in agreement with current theory (which is usually introduced to them after they have done the lab), but rather on their attempts to make sense of their data based on what they currently know. The explanation of data is very difficult for pre-service elementary teachers (and many other college students) because they have been conditioned to produce the “right” answer even if they do not understand what it is or how it was obtained. One of the goals of the lab portion of class is to help students realize that they can collect and critically analyze data themselves, and that lab is for discovery and playing with nature. One important idea that is honored with the homework assignments and labs is to never create busywork for the students, but instead to use assignments and labs that are aids to learning and discovery.
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In the Classroom
Exams for both physics and chemistry consist of multiple choice and short answer–essay questions that explore the students’ knowledge and application of the physical science topics in everyday situations. Students are given old tests to review so that they are fully aware of our testing style (not necessarily the question content) and the format of exams. Review sessions are conducted at the students’ request to help allay their fears and reinforce subject matter. The students’ reactions to the class as evidenced by written class evaluations and verbal comments during the semester have been positive. Students have appreciated the many demonstrations and hands-on laboratory activities. Most importantly, the students indicate that they plan to incorporate what they learned in class into their future classrooms. Comparing a conventional pre-service elementary teacher class with the physics-first class would be worthwhile. However, no formal attempts have been made to compare the outcome of this physics-first approach with the conventional approach to teaching chemistry to pre-service elementary teachers because very few courses in this country are designed to teach chemistry to pre-service elementary teachers. The class described in this paper was created and fought for because of the need to give pre-service elementary teachers a physics and chemistry class that was more suitable for their needs than typical general education classes. Acknowledgments The author acknowledges and thanks the creators of this class, Bradley W. Carroll and Spencer L. Seager, as well as the reviewers, for their helpful comments. Literature Cited 1. 2. 3. 4. 5. 6. 7. 8. 9. 10.
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