Learning By Seeing: Molecular Modeling In High School Science

 

Rosa Hemphill, Oregon Episcopal School, Portland, OR. hemphill@teleport.com

Lori Lancaster, Centennial High School, Portland, OR. llancast@teleport.com

Mike Ellison, Skyview High School, Vancouver, WA. mkellison@worldaccessnet.com

 

 

A “New” Science Teaching Paradigm

Musing on Teaching Introductory Chemical Bonding

 

I. The Scientific Process

A. Observation

B. Seeking Patterns in Observations

C. Explaining the Patterns (Model Building)

D. Making Predictions Based on the Model

E. Testing Predictions by Observations and the Cycle Repeats

 

II. The Teaching Process (Mike’s Utopian Dream version)

A. Observation (Labs)

B. Seeking Patterns in Observations

C. Explaining the Patterns (Model Building)

1. Students Construct Their Own Meaning

D. Making Predictions Based on the Model

1. If I am right, what should happen when...

E. Testing Predictions by Observations and the Cycle Repeats

 

III. Application of “New” Paradigm to Teaching Introductory Chemical Bonding

A. Observations/Patterns

1. Basic Atomic Structure

a. Thomson’s experiment - discovery of electron

b. Rutherford’s Experiment

2. Periodic Trends

a. Stability of Noble Gases

b. Periodicity of most common oxidation states

i. Pattern - Match the number of electrons in a Noble Gas

ii. Can be deduced from data on % composition of representative compounds.

c. Atomic sizes - provide data

d. Ionic sizes - provide data

e. Ionization Energy - provide data

3. Conductivity Observations/ Patterns
(Labs with Vernier probes)

a. Both Ionic and Molecular Substances exist

b. Metal + Nonmetal = ionic

c. Nonmetal + Nonmetal = molecular

 

4. Polar/Nonpolar Solvents - Lab

a. Differences in solubility exist in a continuum

5. Quantum Mechanics

a. Can observe spectra

b. Concept of orbitals and probability plots

B. Hypothesizing (Students)

1. Why are some substances ionic and some molecular?

2. Why are some substances polar and others nonpolar

C. Explanations (Models)

1. Electron Density Visualizations - Spartan or ChemViz

a. Students design experiment

b. Halides and hydrides of 2nd row elements

i. Slices through electron density volumes - see Rosa’s Web page http://www.canby.com/~hemphill/chmimg.html

2. Electron Density Isosurfaces

a. Students design experiment

b. Halides and hydrides of 2nd row elements - see Rosa’s Web page http://www.canby.com/~hemphill/chmimg.html

3. Electrostatic Potential on Mapped Onto Isosurfaces

a. Illustrates polarity of molecules

b. Show dipoles