While there is hope on the horizon in the way these concepts are treated in the NRC Framework and the NGSS, change will not occur without interdisciplinary reforms at the college level to provide support for future teachers and to help students bridge the macroscopic—molecular gap that is so problematic.
This work was supported in part by NSF award The authors thank Sonia Underwood and Nicole Becker for helpful discussions. We also thank Tom Lundy for his work on the design and construction of the molecular interaction applet. That is, it is induced by instruction or the instructor. National Center for Biotechnology Information , U. Melanie M. Michael W. Eric Brewe, Monitoring Editor. Author information Article notes Copyright and License information Disclaimer. Address correspondence to: Melanie M.
Cooper ude. Cooper and M. This article is distributed by The American Society for Cell Biology under license from the author s. It is available to the public under an Attribution—Noncommercial—Share Alike 3. This article has been cited by other articles in PMC.
The Origins of Student Difficulties with Chemical Energy: An Interdisciplinary Problem The inability to understand the origin of the energy changes associated with chemical interactions at the molecular level is a significant impediment to a coherent approach to biological processes and must be addressed explicitly. Biology To understand why many students construct and retain a mental model in which chemical bonds contain energy that is then released as bonds break, we must look at the collective history of how this idea became so prevalent.
Physics As students move through the K—12 system, the more general topic of energy is usually addressed first in courses identified as physics or physical science, meaning that students who take introductory biology and chemistry courses might be expected to have ideas about energy that have been shaped not only by their everyday experiences but by interaction between those ideas and the effects of instruction in the physical sciences.
Chemistry While the foundations of the problem may lie in earlier courses, clearly chemists must take the major responsibility for problems students have with the concept of chemical energy. Potential Energy Is a Problem In most general and organic chemistry courses i. Open in a separate window. Figure 1. The interconnected learning progressions of structure, properties and, energy. Figure 2.
Footnotes 1 Even though London dispersion forces and entropic effects are equally important. Understanding of energy in biology and vitalistic conceptions.
Int J Sci Educ. Student's reasoning about basic chemical thermodynamics and chemical bonding: what changes occur during a context-based post chemistry course? New York: Prentice Hall; Organic Chemistry. On the concept of energy: how understanding its history can improve physics teaching. Sci Educ. Development and assessment of a molecular structure and properties learning progression. J Chem Educ. New York: Addison-Wesley; The Feynman Lectures on Physics. Exothermic bond breaking: a persistent misconception.
Phys Educ. Unpublished master's thesis. Clemson, SC: Clemson University; Assessment of conceptual understanding of atomic structure, covalent bonding, and bond energy. Student interpretations of equations related to the first law of thermodynamics. Force concept inventory. Phys Teach. J Res Sci Teach. Energy and the confused student I: work. Learning and constructivism. Constructivist Instruction: Success or Failure? New York: Routledge; Using student-generated analogies to investigate conceptions of energy: a multidisciplinary study.
Research on student understanding. Am J Phys. Developing a new teaching approach for the chemical bonding concept aligned with current scientific and pedagogical knowledge. Crosscutting Concepts, and Core Ideas. Meaningful learning: the essential factor for conceptual change in limited or inappropriate propositional hierarchies leading to empowerment of learners. Thermal physics in the introductory physics course: why and how to teach it from a unified atomic perspective. Univ Chem Educ.
Developing a hypothetical multi-dimensional learning progression for the nature of matter. Textbook errors and misconceptions in biology: cell energetics. When more bond energies of the bond in different molecules that are taken into consideration, the average will be more accurate.
When a chemical reaction occurs, the atoms in the reactants rearrange their chemical bonds to make products. The new arrangement of bonds does not have the same total energy as the bonds in the reactants.
Therefore, when chemical reactions occur, there will always be an accompanying energy change. In some reactions, the energy of the products is lower than the energy of the reactants. Thus, in the course of the reaction, the substances lose energy to the surrounding environment. Such reactions are exothermic and can be represented by an energy-level diagram in Figure 1 left. In most cases, the energy is given off as heat although a few reactions give off energy as light.
In chemical reactions where the products have a higher energy than the reactants, the reactants must absorb energy from their environment to react. These reactions are endothermic and can be represented by an energy-level diagrams like Figure 1 right. It is not uncommon that textbooks and instructors to consider heat as a independent "species" in a reaction. While this is rigorously incorrect because one cannot "add or remove heat" to a reaction as with species, it serves as a convenient mechanism to predict the shift of reactions with changing temperature.
A more accurate, and hence preferred, description is discussed below. Exothermic and endothermic reactions can be thought of as having energy as either a "product" of the reaction or a "reactant. Endothermic reactions require energy, so energy is a reactant. No calculates are required to address this question. Just look at where the "heat" is in the chemical reaction. Simply multiply the average bond energy of H-Cl by 2.
This is how much energy is needed to break the bonds on the reactant side. Then we look at the bond formation which is on the product side:. This is how much energy is released when the bonds on the product side are formed.
The net change of the reaction is therefore. In short, they are awesome. Brittny But why do some chemical reactions release massive amounts of energy, while others absorb energy? In a chemical reaction, the main change that occurs relates to the way atoms are connected or bonded to each other. In order to change those connections, bonds must be broken and new bonds must be formed. To understand this, consider the chemical reaction between vinegar and baking soda.
The chemical reaction behind this science fair favorite involves baking soda—also known as sodium bicarbonate to chemists—and vinegar, otherwise known as acetic acid. These compounds react to form the molecules sodium acetate, water, and carbon dioxide.
The baking soda and vinegar are called the reactants. The sodium acetate, water, and carbon dioxide that are formed are called the products. Before the atoms in acetic acid and sodium bicarbonate can be rearranged to form the products, some of the bonds between the atoms in those molecules must be broken, and because the atoms are attracted to one another, it takes energy to pull them apart.
Then, when the products are formed sodium acetate, water, and carbon dioxide energy is released because atoms that have an attraction for one another are brought back together. By comparing the energy absorbed when bonds in the reactants are broken with the energy released when bonds in the products are formed, you can determine whether a chemical reaction releases energy or absorbs energy overall.
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