Measuring Student
Understanding of Density,
with Geological Applications
Emily L. Klingler
Master of Science in Teaching
12/16/05
Committee Members:
Dr. Stephen Norton, Department of Earth Sciences
Dr. Peter Koons, Department of Earth Sciences
Dr. John Thompson, Department of Physics and Astronomy
Image from: www.vims.edu/bio/ microbial/NBPice.html
Introduction
• Important physical concept in science
• Density differences drive many Earth
Science processes
• Density “refresher” exercise in ERS 102
laboratory, spring ‘04
Image from: www.vims.edu/bio/ microbial/NBPice.html
Significance of the Study
• Science Education programs and departments of
Physics, Chemistry, and Biochemistry have
undertaken education research studies on density.
• Earth Sciences has few education research studies
on density.
• We have an opportunity to explore the effects of a
revised curriculum.
Background Research
Common student difficulties include:
•Alternate conceptions about volume;
•Confusion between mass and volume;
•Confusion between mass and weight;
•Confusion between mass and density; and
•Alternate conceptions about sorting material by
density.
Image from: www.sdfonline.co.uk/ lotsa/business/weight.htm
Research Question
To what extent does targeted instruction
influence
•
student understanding of density
and
•
the frequency and accuracy with
which students apply their
understanding to explain Earth
Science phenomena?
Methods
Population breakdown (ERS 102):
90% Gen. Ed., 5% future Earth Science majors, 5% other science majors
Title
ERS 102
Semester
Pre-course Post-course
assessment assessment
Function
Group 1 Spring 2004
N = 66
No
Group 2
Yes
Yes
Assessment of change in
understanding from new
laboratory exercise.
Yes
Yes
Assessment of change in
understanding from new
laboratory exercise.
Fall 2004
N = 32
Group 3 Spring 2005
N = 65
YesDevelopment of baseline
questions 1 data and contextual density
to 3
questions.
Methods
The Experiment: Groups 2 and 3
•
Pre-course assessment prior to density laboratory
(10 questions; 3 related to ERS)
•
Specially-designed inquiry-based laboratory
exercise
•
Post-course assessment on last day of laboratory
Image from: http://www.kk.org/cooltools/archives/thinking_putty.png
Sample Density Question
A straight, uniform board is cut into three differently sized pieces. Each
piece has identical width and thickness, but different lengths.
A is shortest, C is longest.
Choices:
Students were asked to identify
the piece with the greatest:
•
•
•
Volume
Density
Mass
And to explain their reasoning.
•
•
•
•
•
Piece A
Piece B
Piece C
They are all the same
Impossible to tell without making
additional measurements
Modified from Yeend, et al., 2002.
Sample Application of Density
What process in Earth’s mantle is thought to cause
plate tectonics? Explain the process fully.
Image from: http://www.dstu.univ-montp2.fr/PERSO/bokelmann/convection.gif
Laboratory Exercise
•
Group discussions of density
•
Creation of a procedure to determine the density
of an irregularly shaped object (e.g., Silly Putty,
bbs, or Silly Putty-bb mixture)
•
Oral presentation of procedure, methods, and
results
•
Revised procedures used with rocks and
constituent minerals
Image from: http://www.newburycomics.com/images/bmh/BU/103-172144NEWBU.jpg
Data Reduction and Analysis
• Reading and classification of responses
• Coding of extended responses for statistical
analysis
Assessment Response Rubric
Level 1: Naïve
•Restating
the question
•Fragmentary sketch
•Incorrect mechanism
Level 2: Intuitive
•Incomplete/incorrect
•Insightful
account
ideas
Level 3: Superficial
•Had
the idea of convection
•Mechanism insufficiently explained
Level 4: In-depth
•Sufficient
explanation of convection (T)
Level 5: Sophisticated
•Unusually
thorough explanation of convection (T,D)
Modified from G. Wiggins and J. McTighe.
Sample Student Response
What process in Earth’s mantle is thought to cause
plate tectonics? Explain the process fully (from Group 3).
Pre-course (level 3)
“The molten rock cools and expands causing pressure within the
Earth’s crust causing the plates to move and separate/overlap.”
Post-course (level 4)
“The convection of magma underneath the crust. It churns and
moves and the layer touching the lithosphere cools down and
attaches itself to it. As the attached magma continues to “churn,”
it pulls along with it the lithosphere causing movement of the plates.”
Results for Plate Tectonics Question
Group 2, N = 32
Group 3, N = 65
•Five more students attempted to
respond to this question on the posttest.
• 13% (4 students) improved from
level 3 to level 4, pre- to post-test.
•No students cited density (level 5).
•23% (5 students) who first scored
at level 3 improved to levels 4 and
5, post-test (one student scored a 5).
Statistically significant improvement
in understanding of mantle
convection/plate tectonics, but no
improvement in understanding the
role of density in that process.
Statistically significant
improvement in understanding of
mantle convection/plate tectonics,
but no major improvement in
understanding the role of density in
that process.
Sample Response to Density Question
A straight, uniform board is cut into three differently sized pieces. Each
piece has identical width and thickness, but different lengths.
A is shortest, C is longest.
Students were asked to identify
the piece with the greatest:
•
•
•
Volume
Density
Mass
And to explain their reasoning.
Choices:
•
•
•
•
•
Piece A
Piece B
Piece C
They are all the same
Impossible to tell without making
additional measurements
Modified from Yeend, et al., 2002.
Sample Response to Density Question
Volume
One student’s improvement, from pre- to postcourse (from Group 3):
Level 4: “The large one [box C] has greater volume
and mass.”
Level 5: “V=LxWxH and the box C has the largest
[volume] because the length is the greatest.”
Sample Response to Density Question
Density
A typical student response at the Sophisticated level
(from Group 2):
Level 5: “D=m/v; lwh=V. Since C had the largest l,
it had the largest V. In order to keep density the
same, its m must also be greater.”
Sample Response to Density Question
Mass
A typical student response at the In-depth level
(from Group 2):
Level 4: “I chose C…because C is the largest
therefore it will weigh the most.”
Results for Basic Density Questions
Question
Group 2, N = 32
Group 3, N = 65
Pre-/ Post-course
Pre-/Post-course
(4) Volume
comparison
Differences in performances Improvement in
not statistically significant.
understanding.
(5) Density
comparison
Differences in
No change in understanding. performances not
statistically significant.
(6) Mass
comparison
No change in understanding, Improvement in
understanding.
but high pre- and postcourse scores.
Sample Multiple-Choice Results
• On questions 4, 5, and 6, most students
chose the correct response on both pre- and
post-course assessments.
(66% to 88%, both groups)
• Few students had the correct response and a
sophisticated (level 5) explanation.
(12% to 41%, both groups)
Conclusions
Earth Science Questions
Group 2
N = 32
Group 3
N = 65
•Significant improvement
on question #1
Basic Density Questions
•Significant improvement
on questions #7 and 9
•Significant consistency on •Significant consistency on
questions #5, 6, and 8
question #3
•Significant improvement
on question #1
•Significant improvement
on questions #4, 6, 7, and 8
•Significant decline in
performance on question
#3
•Significant consistency on
question #9
Conclusions
•Overall
favorable results, but no control groups and
small populations make all conclusions tentative.
•Lack
of pre-course data from Group 1 did not allow for
firm conclusions about the efficacy of the intervention.
•In
the pre-course assessment, students commonly recognized
the correct multiple choice response but showed incomplete
understanding in their explanations.
•In
the post-course assessment, students overall had an
improved level of understanding of density.
Conclusions
Suggestions for future work
•Revise
the assessment and laboratory exercise so that they are
more closely coupled.
•Examine
students’ understanding of volume and mass more
carefully (there was only one question on each subject on
our assessment).
•Revise
other Earth Science laboratory exercises so that they are
more inquiry-based.
Acknowledgments
Committee Members
Dr. Stephen Norton, Department of Earth Sciences
Dr. Peter Koons, Department of Earth Sciences
Dr. John Thompson, Department of Physics and Astronomy
and much advice and help from
Jeff Owen (first M.S.T. grad!)
and
Dr. Phillip A. Pratt, College of Education and Human Development