Models and Modeling in the High School Chemistry Classroom

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Models and ModelingModels and Modelingin the High Schoolin the High School

Chemistry Chemistry ClassroomClassroom

Larry DukerichDobson HSMesa, AZCRESMETArizona State University

Brenda RoyceUniversity HSFresno, CA

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The Problem with The Problem with Traditional InstructionTraditional Instruction Presumes two kinds of knowledge:Presumes two kinds of knowledge:

Facts and ideasFacts and ideas - - thingsthings packaged packaged into words and distributed to students.into words and distributed to students.

Know-howKnow-how - skills packaged as rules - skills packaged as rules or procedures.or procedures.

Assumes students will see the Assumes students will see the underlying structure in the content.underlying structure in the content.

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““Teaching by Telling” is Teaching by Telling” is IneffectiveIneffective

Students…Students… Systematically miss the point of what we Systematically miss the point of what we

tell them.tell them. do not have the same “schema” associated do not have the same “schema” associated

with key ideas/words that we have.with key ideas/words that we have. do not improve do not improve their their problem-solving skills problem-solving skills

by watching the by watching the teacherteacher solve problems solve problems

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Algorithms vs Algorithms vs UnderstandingUnderstandingAlgorithms vs Algorithms vs UnderstandingUnderstanding

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

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

= H

= N

Nitrogen gas and hydrogen gas react to form ammonia gas by the reaction

N2 + 3 H2 2 NH3

The 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?

A B C D

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How Do You Know?How Do You Know?

All students know the All students know the formula for water is Hformula for water is H22O.O.

Very few are able to cite Very few are able to cite any evidence for why we any evidence for why we believe this to be the case.believe this to be the case.

All students know the All students know the formula for water is Hformula for water is H22O.O.

Very few are able to cite Very few are able to cite any evidence for why we any evidence for why we believe this to be the case.believe this to be the case.

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Do They Really Have an Do They Really Have an Atomic View of Matter?Atomic View of Matter? Do They Really Have an Do They Really Have an Atomic View of Matter?Atomic View of Matter?

Before we investigate the inner workings of the atom, let’s 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 model.

Before we investigate the inner workings of the atom, let’s 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 model.

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Representation of MatterRepresentation of Matter

Question: “What’s happening at the simplest level of matter?”

Question: “What’s happening at the simplest level of matter?”

More More StoryboardsStoryboards

Gas Diffusion: Gas Diffusion: Where’s The Air?Where’s The Air?

Aqueous Diffusion: Aqueous Diffusion:

The Continuous The Continuous Model of MatterModel of Matter

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Where’s the Evidence?Where’s 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.

What’s gained by telling a Cliff’s Notes version of the story of how our current model of the atom evolved?

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.

What’s gained by telling a Cliff’s Notes version of the story of how our current model of the atom evolved?

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Construct and useConstruct and use scientific models to describe, scientific models to describe, to explain, to predict and to control physical to explain, to predict and to control physical phenomena.phenomena.

Model physical objects and processes using Model physical objects and processes using diagrammatic, graphical and algebraic diagrammatic, graphical and algebraic representations.representations.

Recognize a small set of particle models as the Recognize a small set of particle models as the content corecontent core of chemistry. of chemistry.

Evaluate scientific models through comparison Evaluate scientific models through comparison with empirical data.with empirical data.

View modeling as the View modeling as the procedural coreprocedural core of scientific of scientific knowledgeknowledge

InstructionalInstructional ObjectivesObjectives

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What Do We Mean by What Do We Mean by Model?Model?

Models are representations of structure in a physical Models are representations of structure in a physical system or processsystem or process

Symbolic Representations

PhysicalSystem

MentalModel

Verbal

Algebraic

Diagrammatic

Graphical

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Why Models?Why Models?Why Models?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 Microscopic representations Symbolic representations

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 Microscopic representations Symbolic representations

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Why modeling?!Why modeling?! To help students see science as a way of To help students see science as a way of

viewing the world rather than as a collection of viewing the world rather than as a collection of facts. facts.

To make the To make the coherencecoherence of scientific knowledge of scientific knowledge more evident to students by making it more more evident to students by making it more explicit.explicit.

Models and SystemsModels and Systems are explicitly recognized are explicitly recognized as major unifying ideas for all the sciences by as major unifying ideas for all the sciences by the the AAAS Project 2061AAAS Project 2061 for the reform of US for the reform of US science education.science education.

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Uncovering ChemistryUncovering 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’

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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Particle Models of Gradually Increasing Complexity

Particle Models of Gradually Increasing Complexity Begin with phenomena that can be

accounted for by simple BB’s Conservation of mass Behavior of gases - KMT

Recognize that particles DO attract one another “Sticky BB’s” account for behavior of

condensed phases

Begin with phenomena that can be accounted for by simple BB’s Conservation of mass Behavior of gases - KMT

Recognize that particles DO attract one another “Sticky BB’s” account for behavior of

condensed phases

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Models Evolve as Need ArisesModels 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 explain Conductivity of solutions Properties of ionic solids

Develop model of atom that can acquire charge after you examine behavior of charged objects

Atom with + core and mobile electrons should explain Conductivity of solutions Properties of ionic solids

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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

surroundings

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

surroundings

Energy - Early and OftenEnergy - Early and Often

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Reconnect Eth and EchReconnect Eth and Ech

Particles in system exchange Ek for Ech to rearrange atoms

181 kJ + N2 + O2 ––> 2 NO

Representation consistent with fact that an endothermic reaction absorbs energy, yet the system cools

Particles in system exchange Ek for Ech to rearrange atoms

181 kJ + N2 + O2 ––> 2 NO

Representation consistent with fact that an endothermic reaction absorbs energy, yet the system cools

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How to Teach it?How to Teach it?

constructivist vs transmissionistconstructivist vs transmissionist

cooperative inquiry vs lecture/demonstrationcooperative inquiry vs lecture/demonstration

student-centered vs teacher-centeredstudent-centered vs teacher-centered

active engagement vs passive reception active engagement vs passive reception

student activity vs teacher demonstrationstudent activity vs teacher demonstration

student articulation vs teacher presentationstudent articulation vs teacher presentation

lab-based vs textbook-basedlab-based vs textbook-based

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Be the “Guide on the Side”Be the “Guide on the Side”

Don’t 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

Don’t 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

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Preparing the WhiteboardPreparing the Whiteboard

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Making PresentationMaking Presentation