Chem Connections


Why does the Ozone Hole Form?

Ozone Image


zone

Prerequisites: Knowledge of stoichiometry, gases, thermochemistry, bond energies, atomic theory, interaction of light with matter, bonding and structure (Lewis structures, s and p bonding, orbital overlap, and 3D geometry).
Interdisciplinary aspects: As you learn about the chemistry of the ozone hole, you will also learn how it overlaps with other disciplines and areas of your life, including atmospheric chemistry, global climate, environmental and earth systems science, public policy, international treaties, and the media.
Classroom, laboratory, or both: Both
Number of one-hour class periods: 9 - 10
Number of 3-4 hour laboratory periods: 3

Trish Ferrett (Carleton College)
Sharon Anthony (Beloit)
Interdisciplinary consultant and Co-author:
Ron Cohen (U.C. Berkeley)
Susan Strahan (NASA Goddard)
and others at NASA

Description

This module is driven by the question, "Why does the ozone hole form in the Antarctic Spring?" Students will use the world wide web to learn about the structure of the atmosphere and the ozone layer, when the ozone hole is formed, and its current status. The oxygen chemistry which "naturally" makes and destroys ozone will be covered, along with the 2-step Cl-catalyzed cycle proposed in 1974 by Rowland and Molina. The unique Antarctic meteorology and heterogeneous chemistry will complete the story. Emphasis is placed on using chemical kinetics in a real context by using rate concepts and calculations to answer relevant questions about ozone. The skill of learning to support or refute a scientific hypothesis with evidence is strongly emphasized throughout, as well as the interplay of experimental data and theoretical models.

Tool Kit:
Chemical Principles:

  • Chemical Kinetics: Rate law, rate constant, rate calculations; activation energy; Arrhenius equation; reaction coordinate diagrams, isolation and initial rates methods for measuring rates.
  • Reaction mechanisms: elementary steps, collision types (bimolecular, termolecular); radical reaction mechanisms.
  • Interaction of light with matter: UV-Vis spectroscopy; photochemistry (bond breakage).
  • Special topics: satellite and ground-based measurements of ozone, atmospheric structure and dynamics, CFC properties and chemistry, catalytic cycles for ozone destruction, Chapman oxygen chemistry, heterogeneous chemistry on clouds, Antarctic meteorology.

Thinking Like a Scientist:

  • Reading and writing skills: arguing from evidence to support or refute a hypothesis, explaining concepts, summarizing logic and evidence of a scientific argument.
  • Data analysis and interpretation: quantitative and qualitative.
  • The application of models: including an understanding of cause and effect versus correlation, comparisons to data, and evaluation of models and predictions.
  • Science literacy: including an ability to analyze a media presentation.
  • World Wide Web skills

Audience: This module is designed to be covered at the end of the first term or in the second term of general (first-year) chemistry.

Materials to be developed

A roadmap for instructors to follow, historical introduction to the topic with modern developments at NASA, reading materials, strategies for mediating class work style and discussions within this pedagogy, data from the primary literature and Internet, laboratory exercises aimed at analyzing Internet/literature data, list of resources including current investigators in the field and progress reports from NASA.


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Last modified: 10/18/00 at 2:15 PM