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Models and Modeling in the High School Chemistry Classroom


Models and Modeling in the High School Chemistry Classroom Larry Dukerich Modeling Instruction Arizona State University First some background on what is the problem ... – PowerPoint PPT presentation

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Title: Models and Modeling in the High School Chemistry Classroom

Models and Modelingin the High SchoolChemistry

Larry Dukerich Modeling Instruction Arizona State
Traditional Instruction
  • Presumes two kinds of knowledge
  • Facts and ideas - things packaged into words and
    distributed to students.
  • Know-how - skills packaged as rules or
  • Assumes students will see the underlying
    structure in the content.

Teaching by Telling is Ineffective
  • Students
  • Systematically miss the point of what we tell
  • do not have the same schema associated with key
    ideas/words that we have.
  • do not improve their problem-solving skills by
    watching the teacher solve problems

Algorithms vs Understanding
  • What does it mean when students can solve
    quantitative problems, but cannot answer the

Nitrogen gas and hydrogen gas react to form
ammonia gas by the reaction N2 3 H2 ? 2
NH3The box at right shows a mixture of nitrogen
and hydrogen molecules before the reaction
begins. Which of the boxes below correctly shows
what the reaction mixture would look like after
the reaction was complete?
How Do You Know?
  • All students know the formula for water is H2O.
  • Very few are able to cite any evidence for why we
    believe this to be the case.

Do They Really Have an Atomic View of Matter?
  • Before we investigate the inner workings of the
    atom, lets first make sure they really believe
    in atoms.
  • Students can state the Law of Conservation of
    Mass, but then will claim that mass is lost in
    some reactions.
  • When asked to represent matter at sub-microscopic
    level, many sketch matter using a continuous

Representation of Matter
  • Question Whats happening at the simplest level
    of matter?

More Storyboards Gas Diffusion Wheres The
Air? Aqueous Diffusion The Continuous Model
of Matter
Wheres the Evidence?
  • Why teach a model of the inner workings of the
    atom without examining any of the evidence?
  • Students know the atom has a nucleus surrounded
    by electrons, but cannot use this model to
    account for electrical interactions.
  • Whats gained by telling a Cliffs Notes version
    of the story of how our current model of the atom

Seeing is Believing?
  • Because students have trouble relating
    microscopic and macroscopic views, we start our
    discussion with the atom and bypass the
    traditional historical approach taken by many
    texts. (This is not to say that we do not value
    the study of the history of chemistry in fact,
    we believe that history helps the material come
    alive.) Pictures from scanning tunneling
    microscopes can now show us atoms. Therefore,
    we begin with We believe in atoms because we can
    see them.

Teaching Tip from World of Chemistry, Zumdahl,
Zumdahl, DeCoste, McDougall Littell, 2007
I See It Because I Believe It

Instructional Objectives
  • Construct and use scientific models to describe,
    to explain, to predict and to control physical
  • Model physical objects and processes using
    diagrammatic, graphical and algebraic
  • Recognize a small set of particle models as the
    content core of chemistry.
  • Evaluate scientific models through comparison
    with empirical data.
  • View modeling as the procedural core of
    scientific knowledge

What Do We Mean by Model?
  • Models are representations of structure in a
    physical system or process

Why Models?
  • Models are basic units of knowledge
  • A few basic models are used again and again with
    only minor modifications.
  • Models help students connect
  • Macroscopic observations
  • Sub-microscopic representations
  • Symbolic representations

Why Modeling?!
  • To help students see science as a way of viewing
    the world rather than as a collection of facts.
  • To make the coherence of scientific knowledge
    more evident to students by making it more
  • Models and modeling figure prominently in the

Uncovering Chemistry
  • Examine matter from outside-in instead of from
  • Observable Phenomena ? Model
  • Students learn to trust scientific thinking, not
    just teacher/textbook authority
  • Organize content around a meaningful Story of

Particle Models of Increasing Complexity
  • Begin with phenomena that can be accounted for by
    simple BBs
  • Conservation of mass
  • Behavior of gases - KMT
  • Recognize that particles DO attract one another
  • Sticky BBs account for behavior of condensed

Models Evolve as Need Arises
  • Develop model of atom that can acquire charge
    after you examine behavior of charged objects
  • Atom with core and mobile electrons should
  • Conductivity of solutions
  • Properties of ionic solids

Energy - Early and Often
  • Make energy an integral part of the story line
  • Help students develop a coherent picture of the
    role of energy in changes in matter
  • Energy storage modes within system
  • Transfer mechanisms between system and

Reconnect Eth and Ech
  • Particles in system exchange Eth for Ech to
    rearrange atoms
  • 181 kJ N2 O2 gt 2 NO
  • Representation consistent with fact that an
    endothermic reaction absorbs energy, yet the
    system cools

How to Teach it?
constructivist vs
transmissionist cooperative inquiry vs
lecture/demonstration student-centered vs
teacher-centered active engagement vs
passive reception student activity
vs teacher demonstration student articulation
vs teacher presentation
lab-based vs textbook-based
Be the Guide on the Side
  • Dont be the dispenser of knowledge
  • Help students develop tools to explain behavior
    of matter in a coherent way
  • Let the students do the talking
  • Ask, How do you know that?
  • Require particle diagrams when applicable

Preparing the Whiteboard
Making the Presentation