A Modeling Approach to Science Teaching

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A Modeling Approach to Science Teaching
Nicholas Park Greenhill School
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A Private Universe

• We go through life collecting memories, and
  organizing them into mental models, or schema.
• Our memory depends on connections new inputs
  which do not fit in an existing schema tend to be
  forgotten.
• It takes a very discrepant phenomenon to motivate
  a change in existing schemata.

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Science and Modeling

• Scientists construct and use shared models to
  describe, explain, predict and control physical
  sytems.
• By making this process explicit, we help students
  to
• Revise their mental schemata (models) in the
  light of experimental evidence and collaborative
  discourse
• Understand the scientific process

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What Do We Mean by Model?

• Essential and non-essential elements of a
  physical system or process are identified
• Models are used to represent the structure
  underlying the essential elements

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Why Models?

• Models are basic units of knowledge
• A few basic models are used again and again with
  only minor modifications.
• Students DO work from mental models the
  question is which model it will be
• A shared, rigorous model with explicit
  experimental support?
• An inconsistently applied, private model based on
  miscellaneous experiences.

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What about problem solving?

• The problem with problem-solving
• Students come to see problems and their answers
  as the units of knowledge.
• Students fail to see common elements in novel
  problems.
• But we never did a problem like this!
• Models as basic units of knowledge
• A few basic models are used again and again with
  only minor modifications.
• Students identify or create a model and make
  inferences from the model to produce a solution.

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What doesnt work

• Presentation of facts and skills, with the
  assumption that students will see the underlying
  structure in the content.
• They systematically miss the point of what we
  tell them.
• They do not have the same schema associated
  with key ideas/words that we have.
• Students passively listen while T works

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What works

• Interactive engagement
• Student discourse articulation
• Cognitive scaffolding
• Multiple representational tools
• Consensus-based model building
• Explicit hierarchal organization of ideas and
  concepts into models

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The Modeling Method

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

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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
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The Modeling Cycle
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I - Model Development

• Students in cooperative groups
• design and perform experiments.
• formulate functional relationship between
  variables.
• evaluate fit to data.
• Post-lab analysis
• whiteboard presentation of student findings
• multiple representations
• justification of conclusions

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II - Model Deployment

• In post-lab discussion, the instructor
• brings closure to the experiment.
• fleshes out details of the model, relating common
  features of various representations.
• helps students to abstract the model from the
  context in which it was developed.

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II - Model Deployment

• In deployment activities, students

• learn to apply model to variety of related
  situations.
• identify system composition
• accurately represent its structure

• articulate their understanding in oral
  presentations.

• are guided by instructor's questions
• Why did you do that?
• How do you know that?

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Modeling in a Nutshell

• Through carefully guided discourse, students
  construct shared models, using various
  representations, to describe shared experiences
  with physical systems and processes.
• Let the students do the talking
• Ask, How do you know that?
• Require diagrams and representations whenever
  possible

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Chemistry

• A Closer Look

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Algorithms vs Understanding

• What does it mean when students can solve
  stoichiometry problems, but cannot answer the
  following?

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?
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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.

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Do They Really Have an Atomic View of Matter?

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

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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.
• Why disconnect the Bohr model of the atom from
  the effort to understand the hydrogen line
  spectrum?

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Uncovering Chemistry

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

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Sample Cycle Density

• Prerequisite activities
• Define volume by counting cubes, and validate
  the formulas learned in math.
• Define mass as amount of matter, measured using a
  balance.
• Develop law of conservation of mass through a
  lab with physical and chemical changes

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Sample Cycle Density

• Density Lab and Follow-up
• Question What is the relationship between the
  mass of a solid and its volume?

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• Even if students correctly say mass per unit
  volume rather than mass per volume in
  interpreting M/V, there is no conclusive
  assurance that they really understand the
  meaning. Some do, but others have merely
  memorized the locution. It is important to lead
  all students into giving simple interpretation in
  everyday language before accepting a regular use
  of per. Many students do not know what the
  word ratio means. Those having difficulty with
  reasoning and interpretation should always be
  asked, at an early stage, for the meaning of the
  word if they, the text, or the teacher invoke
  it.
• A Arons, Teaching Introductory Physics, John
  Wiley Sons, 1997.

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• In worksheet 3 students make comparisons of the
  mass, volume and density of pairs of objects
  based on particle representations.
• Worksheet 4 further reinforces the notion that
  the slope of a graph has physical meaning.
• The first quiz requires students to determine the
  slope and perform standard calculations involving
  density.
• In next activity Density of a gas, students
  determine the density of carbon dioxide. The
  fact that the value is 3 orders of magnitude
  smaller than that of liquids and solids sets the
  stage for the discussion of an atomic model of
  matter that accounts for this difference.

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Recap What works

• Interactive engagement
• Student discourse articulation
• Cognitive scaffolding
• Multiple representational tools
• Consensus-based model building
• Explicit hierarchal organization of ideas and
  concepts into models

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For more information

• Local workshops next summer (hopefully!) in
  physics, chemistry, and physical science.
• Modeling curricula do an excellent job sequencing
  the curriculum to provide a good storyline and to
  facilitate model construction and deployment.
• Elements of the modeling approach can be adapted
  to any curriculum.
• I am happy to provide advice, resources, or
  assistance.