Using Body Geometry for Teaching Molecular Geometry
Lizabeth T. Ronquillo and James E. Becvar
Department of Chemistry, University of Texas at El Paso, 500 W. University Ave. El Paso, Texas 79968
Abstract
Th
e “Plus-Two” Peer-Led Team Learning (PLTL) Workshop
Program in Chemistry at the University of Texas at El Paso (UTEP)
received the Texas Higher Education Coordinating Board STAR Award in
2006. All students enrolled in general chemistry at UTEP participate in
this innovative intervention in learning. Over the past nine years, the
passing rate has dramatically increased (from about 53% to over 65%)
because of the establishment of PLTL and the enhanced learning
opportunity the PLTL process affords to the normal college chemistry
course experience. Workshop at UTEP is a weekly two-hour, hands-on,
mind-engaged, small-group, student-centered, active learning session
which replaces one hour of lecture per week. Each Workshop session is
overseen entirely by a ‘more-able peer’, an undergraduate student (the
peer leader) who has previously done well in the course. One common
problem for students in general and organic chemistry is the
understanding and use of geometries of bonded molecules. Body
Geometry was created to encourage students to get in teams, pool their
knowledge, and figure out how to form the electronic and/or molecular
arrangement around a given atom in a molecule using their feet, hands,
navels, and heads to show the atomic and lone pair arrangement in
space. This activity has also proven to spur student interest in
understanding the concepts of hybridization, bond angles, isomers, and
diasteriomers. Body Geometry creates an exciting learning experience
for the peer leader and students.
Results
Body Geometry works as a primary tool for teaching the
basis of molecular shape as well as a “refresher” and
supplement in organic chemistry toward the study of
chemical reactivity and reaction mechanisms. The greatest
advantage of using this technique is providing students a fun
and interactive learning environment. Body Geometry is
designed to reinvent learning from stationary passive
absorbance to interactive and exciting concept application.
Stick figures and modeling kits are less memorable than
simplified physical manifestations at test time and for future
chemical exploration. Several learning advantages have come
by integration of the “Plus-Two” PLTL model including
increasing the passing rate, increasing enrollment in STEM
majors, and provided a platform for future success for both
peer leaders and enrolled students.
Cyclopropane
CHEM 1305 Pass Rate (A+B+C) on First Attempt
90
Chemistry Majors at UTEP
84.2%
Methods:
•Begin by forming teams of about 3 to 5 people, based
on workshop numbers.
•Provide an easier molecule (i.e. H2O, NH3, CH4) and
have the team draw the Lewis structure. Check that
they are all correct.
•Now give them a chance to try both drawing and
modeling the possible geometries within these
molecules.
•Geometries up to five bonded atoms with the navel as
the central atom can be formed by one person.
Octahedral centers or multiple atom geometries
require people working together.
•Once teams have established how the shapes look
they can be challenged to demonstrate shapes of more
complicated atom bonding as well as other entire
molecules.
•Students can be provided problems that prompt
questions related to the difference between electronic
and molecular geometry, bond angles, sigma and pi
character of the bond, hybridization, enantiomers, and
diasteriomers.
Percentage (A+B+C)
(Annual total enrollment in parentheses)
Tetrahedral geometry
two enantiomers
Benzene
74.5%
(443)
70
72.2%
237
250
(614)
80
73.4%
(628)
205
74.6%
200
(677)
155
(571)
60.7%
150
111
60
56.8% 56.5%
(435)
(407)
50
55.9%
(389)
51.4% (347)
85
100
52.6%
(627)
(405)
41
50
43.4%
46
53
2001
2002
(371)
40
0
94-95 95-96 96-97 97-98 98-99 99-00 00-01 01-02 02-03 03-04 04-05 05-06
2000
Academic Year
2003
2004
2005
2006
2007
Degrees Awarded By x Years After Enrollment in General Chemistry
70%
60%
55%
50%
40%
49%
44%
45%
38%
30%
20%
44%
36%
42%
58%
52%
41%
33%
25%
27%
4 yrs
4 1/2 yrs
5 yrs
26%
10%
0%
1997-98 (n=347) 1998-99 (n=399) 1999-00 (n=541) 2001-02 (n=495) 2002-03 (n=553)**
Trigonal
Bipyramidal
Geometry
Acknowledgements:
Tetrahedral
Geometry
Ethyne
•NSF STEP Grant ‘Project I-STAR’, DUE 0653270
•UTEP College of Science
• UTEP Chemistry Department
• UTEP Honors Program
• Rio Grande Valley Section of ACS
• And the wonderful students and peer leaders who
provide the basis for improving the educational tool s
we have for the future through this innovative program.
Contacts: Lizabeth Ronquillo, [email protected] or
James Becvar, [email protected]