Forging Chemical Connections among the Symbolic,

Macroscopic, and Microscopic Realms: Getting Students to

Visualize and Understand Using TechnologyScott A. Sinex

Barbara A. GagePrince George’s Community

CollegePresented at the Middle Atlantic Regional Meeting of the American Chemical

Society held at Princeton University, Princeton, NJ, 9-11 June 2003

NH3N2 & H2

A World of Symbolism

N2(g) + 3H2(g) 2NH3(g)

What is the difference between the contents of the two

boxes?What happens if the substances in the first box react?What if one substance occurs in excess?

As chemists, we employ models

• Physical models – wooden ball & stick or the syringe

• Conceptual models – “molecules in the box”

• Mathematical models – Boyle’s Law or Beer’s Law

P

V

PV = k

Calibration CurveA = mc

0.00

0.20

0.40

0.60

0.80

1.00

0.00 0.10 0.20 0.30 0.40 0.50 0.60

Concentration (M)

Ab

sorb

ance

Beer’s Law – How do they grasp?

Beer’s Law Simulator

N2 (g) + O2 (g) 2NO (g)

What happens if

you get this?

Microscopic – the particulate

nature of matter

Macroscopic - observations or results of an

experiment

Symbolic – mathematical equation or chemical equation

  The Three Realms of The Three Realms of ChemistryChemistry

The atomic level(abstract)

How we represent it

The visible world orHow we SEE it

What is the mental model that our students

have?

Building an understanding…

• Conceptual – static dynamic

• Mathematical (using algebra)– discover relationships from data

• Connecting the realms– macroscopic, microscopic, symbolic

…and following national standards!

The chemist’s toolbox…• Graphing calculator/Excel – data handling,

analysis, and modeling

• Chime – interactive molecular models in web-based activities

• Spartan – model building, animations

• Stella/Interactive Excel – mathematical simulations

• Netlogo/Java applets – particle/reaction simulations

• PowerPoint – animated discussion/elaboration and interactive tutorials

Support documents for students…

• Chime - HTML interactive online• TI-83 Graphing Calculator – pdf file• Excel – pdf file• PowerPoint – pdf file• Stella – for using simulations – pdf file• Spartan – on organic lab manual CD

http://academic/pgcc.edu/psc

A journey into molecular geometry…

Styrofoam balls and toothpicks

Ball & stick models

Chime molecules

Lone pair distortion

Molecular polarity

Ideal geometries

Construct and discover

Ideal geometries

Boiling Points of Homologous Series

-200

-150

-100

-50

0

50

100

150

200

250

0 2 4 6 8 10

Number of Carbon in Chain

Boi

ling

Poin

t (o

C)

alkane alcohol thiol

0

50

100

150

200

0 2 4 6 8 10Number of Carbon in Chain

Mol

ar M

ass

alkane alcohol thiol

CH4

CH3OHCH3SH

Boiling Point Trends

Molecular polarity activity

Advantages of Chime

• Freeware – plug-in for Internet Explorer or Netscape

• Use freestanding in web browser software or web pages

• Interactive – positioning and measurements (distances, angles)

• Multiple representations of molecules• Electrostatic potentials maps - polarity• Animations – reaction mechanisms or

vibrations

The wooden ball and

stick model

Computer-generated model

(Spartan 02)

Compare and contrast the internal rotation of the O-O bond

indi-t-butyl peroxide

Dance of the Molecule

What does technology provide…

• Interactive and dynamic visualization• Mathematical modeling and simulations• Measurements – bond distances and angles• Multiple representations• Animations of vibrations • Illustration of reaction

mechanisms• Examination of more

complicated molecules Avoiding this mental model

The classroom…• Becomes more learner-centered• Models discovery learning and science

process• Involves investigative learning activities that

strengthen problem solving skills through data-driven modeling and use of the WWW

• Promotes more discussion and elaboration and utilizes less lecture

• Provides more connections to biological molecules

Contact information

Scott Sinexssinex@pgcc.eduhttp://academic.pgcc.edu/~ssinex

Barbara Gagebgage@pgcc.eduhttp://academic.pgcc.edu/~bgage

College Pathways to the ScienceEducation Standards (NSTA, 2001)