Activity Number
44
Editable
Overview and Learning Objectives
Classroom Practice
Central Concepts
Textbook References
Activity Credits
Requirements

Chemical Reaction Kinetics: Dissociation and Recombination of Diatomic Molecules (a 1-page exploration)

Interactive model, with minimal support

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Overview and Learning Objectives

This model shows the dissociation and recombination of diatomic molecules. When the temperature rises, the diatomic bonds start to break, resulting in free radicals. When the temperature drops, the free radical starts to recombine and form diatomic bonds again. To provide the energy for dissociation and maintain the thermal stability of the recombined molecules, a heat bath is applied. This model can be used to explain a class of reactions, such as O2-->2O, H2-->2H.

Students will understand that:

The dissociation energy for a chemical bond is the amount of energy needed to fracture it;

Free radicals are formed in the process of chemical reactions.

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Classroom Practice

A metaphor for students? Chemical reactions can be regarded as the processes of changing partners of atoms. A partnership between a pair of atoms is typically a covalent bond. The collision theory suggests that atoms bind with others, or lose partners, or swap partners, or do nothing when they collide.

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Central Concepts

Key Concept:

Chemical reactions result from making and breaking chemical bonds. The number of each kind of atom in a reaction remains constant. There are two types of two-body elementary reactions: breaking and making a bond. The rule for breaking a bond is simple: a bond is broken only when enough energy is given to a bonded party for escaping the potential well formed by its binding partner.

Diatomic molecules that disassociate create free radicals. Free radicals react easily with molecules and other radicals.

Additional Related Concepts

Physics/Chemistry

  • Association
  • Breaking bonds
  • Range of reactions
  • Reaction rate

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Textbook References

  • Biology: Concepts and Connections (Pearson) 5th Edition - Chapter 5: The Working Cell
  • BSCS Blue (8th Edition) - Chapter 12: Reproduction
  • BSCS Blue (8th Edition) - Chapter 2: Energy, Life and the Biosphere
  • BSCS Human - Chapter 9: The Cycling of Matter and the Flow of Energy in Communities
  • Cell Biology (Pollard and Earnshaw) Saunders 2002 - Chapter Three: Basic Biophysical Concepts
  • Web of Life - Chapter 4: Photosynthesis and Cellular Respiration

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Activity Credits

Created by CC Project: CCATOMS using Molecular Workbench

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Requirements

  • Java 1.5+ - Java 1.5+ is available for Windows, Linux, and Mac OS X 10.4 and greater. If you are using Mac OS X 10.3, you can download MW Version 1.3 and explore within it instead.

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NSF Logo
These materials are based upon work supported
by the National Science Foundation under grant numbers
9980620, ESI-0242701, EIA-0219345, DUE-0402553, and 0628181.

Any opinions, findings, and conclusions or recommendations expressed in this
material are those of the author(s) and do not necessarily reflect
the views of the National Science Foundation.