Judith Nuño

USC Rossier School of Education

CTSE 507:Issues, History, and Rationale of Science Education

September 11, 1997

1. The Nature of Science: Students should be aware that science is both a way of knowing about the natural world and a body of knowledge, that it is characterized by certain standards of analysis and peer review, and that it is a distinctly human endeavor.

2. Types of Chemistry and Examples of What Chemists Do: Students should know that there different branches of chemistry, that there are many different type of chemists, and that chemists function in research, teaching, and industry. Of interest would be chemists in the food or cosmetic industry, those involved in mining operations, those that study and create synthetic gems, those involved in materials science, those that work with explosive substances, etc.

3. The Nature of Matter: Since chemistry is defined as the science of matter, the nature of matter should be a starting point for the class. Students should be aware that matter is anything that has mass and occupies space. Obviously, the concepts of mass and space should be considered in developing a sense of the nature of matter. The nature of pure substances (elements and compounds), that they are characterized by intrinsic and extrinsic physical properties, and the differences between pure substances and mixtures would fall into this category. Specific physical properties, how to determine or measure them, and how to use them to identify or differentiate substances would all be included int his topic

5. What models are and how they are used in chemistry: Since most of what is "known" about the structure and behavior of matter is based on the indirect measurement of "something" that acts as invisible particles and since the description of this behavior by chemists conforms to a model or models of what this "something" appears to be, the nature of models and modeling is actually integral to the understanding to both chemistry and how a chemist views the world. I think a chemistry teacher should emphasize what a model is, what it can and cannot do and how it is used to explain the behavior of something that cannot be directly seen. Practice in "black box" and indirect measurement activities and in developing models is essential.

5. Phases and Physical Properties of Matter (gas, liquid, solid): Chemistry students usually are able to list the phases of matter, can even describe their characteristics, but rarely are able at the onset to describe their behavior in terms of what is happening on the "unseen" level. Here the particulate model of matter can be introduced with an exploration of the physical properties of the different phases, and a broader discussion of the Kinetic Molecular Theory, a central concept in both chemistry and physics. This theory underscores how energy affects matter and is used to explain the behavior of gases, liquids, and solids.

6. History of Atomic Models: Chemistry students often assume that the model of the atom with a nucleus containing neutrons and protons and electrons moving around the outside is the "true" and only concept of the atom, usually since it is taught as a fact and not as a model. A history of the development of the modern atomic model from the time of John Dalton, with an emphasis on the types of observations used in the formation of each model, contributes to an understanding of the nature of scientific inquiry, its dependence on time and place, and the creativity involved. A model is only as good as the data used to build it and the instruments used to generate the data.

7. Atomic Structure (nucleus, protons, neutrons, electrons): The current model of the structure of the atom, with specific details about the nucleus, protons, neutrons, electrons, energy levels, electron configuration, and the role of electrons in chemical reactivity is the central, unifying idea in chemistry. The formation of ions and isotopes would be part of this topic.

8. The Periodic Table (Development, Use, and Periodic Trends) : The periodic table is a key tool and source of information in chemistry. Knowledge about its development teaches about the nature of science. A literate person, in science or otherwise, should at least recognize the chart. A student of chemistry should know how to use the chart to find an element by its symbol, determine the atomic number and atomic mass, and recognize characteristics of chemical families, understand and describe periodic trends, and predict reactivity from position in the chart, and recognize that placement on the chart is not random but based on atomic structure (electrons).

9. Chemical Symbols and Formulas: Chemistry has a specific language based on symbols for the chemical elements. Students should know the symbols for common elements, be able to find the symbols on a periodic chart, and use them correctly to write the formulas for elements and compounds. Knowledge of how ionic compounds are named and the use of ionic charge to write the formulas is essential if students are to be able to read and write chemical equations.

10. Chemical Bonding (types of bonds and role of electrons in bonding): Differences between ionic and covalent bonds, types of covalent bonds, and the nature of metallic bonds are key to understanding the behavior of different substances. There are different ways to model how the bonds form; I am most comfortable with the Lewis dot method. But an understanding of the differences in the types of bonds, their electrical nature, and how this affects their behavior and reactivity are essential.

11. Chemical Properties of Matter, Characteristic Signs of Chemical Changes, Types Chemical Reactions, and Factors Affecting Reactions: Students should be able to recognize when a chemical change is occurring or has occurred. Not all chemicals explode when they react, even though this is what they most want to see and do. Students should also be able to recognize the difference between a physical and a chemical change. Chemical reactions are the heart of chemistry and students should be able to differentiate between synthesis, decomposition, and displacement reactions.

13. Chemical Equations (write, translate symbols, and balance): This is the language in which chemistry is communicated. An understanding of what the chemical equation represents and how it is used qualitatively to describe a reaction and quantitatively to predict the masses of reactants and products is central to chemical knowledge.

14. Mass, Moles, and Avogadro’s Number: Matter is measured in mass and in moles. The mole is the basic quantitative unit used in chemistry. It can be related to the particulate model of matter. Avogadro’s number is a neat number anyway, even if it is too big to really comprehend. But its use underscores the nature of the "invisibleness" of atoms. Calculation of atomic mass and formula mass would be part of this concept.

15. Mass Relations (stoichiometric relationships---calculation of theoretical yield, limiting reactant, and percent yield): Since college chemistry courses assume that entering freshmen know how to do these kinds of problems, they need to be taught. This is probably the hardest part of the chemistry course, for my students at least.

16. Acids and Bases: The mathematics of acids and bases is frequently difficult for beginning chemistry students to understand let alone master, but they should be aware of the hydrogen and hydroxide ion differences between acids, bases and neutral substances, what the pH scale reads, and how indicators are used to determine pH. This can be taught using household substances, by real or simulated acid rain studies, or by environmental monitoring studies.

17. Carbon Chemistry: An understanding of the special properties of the carbon atom and its central role in organic substances is essential since the people studying chemistry are constructed of carbon-based molecules. I usually end the chemistry course with simple organic nomenclature, which I treat as a problem-solving game or puzzle. The students find this refreshingly easy after stoichiometry and gas laws, but this is probably because by this time of the year they actually have some understanding of chemistry. The nomenclature exercises lead to discussions of nutrition and food testing lab activities, followed by discussions of drug structure and effects. Again, by this time of the year the students known the language of chemistry and can "read" and understand structural formulas that were incomprehensible at the beginning of the year.

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Bibliography

California Draft Physical Science Content Standards. (1997).

K-12 General Guidelines for Science. (1995). Los Angeles, CA: Archdiocese of Los Angeles Department of Catholic Schools.

National Research Council. National Science Education Standards (Draft). (1994).

Washington, D. C. : National Academy Press.

Nuño, Judith S. (1997). "Syllabus for Chemistry," Mary Star of the Sea High School, San

Pedro, California. (Unpublished)

Nuño, Judith S. (1997). "Syllabus for Honors Chemistry," Mary Star of the Sea High

School, San Pedro, California. (Unpublished)

Science Curriculum Framework and Criteria Committee. (1990) .Science Framework for California Public Schools Kindergarten Through Grade Twelve. Sacramento, CA: California Department of Education.