Chemistry 211
Fall 2009
Interpretation of Data
SUMMARY OF CLASS DISCUSSION
Data
Table 1: Boiling Points (Bps) of Some Organic Compounds
Bp
Compound
Molecular Structure
(˚C)
MODEL
Interpretations:
1. The data in Table 1 indicate that Bps of all organic compounds increase
as the molecules increase in size.
H
H
1-pentene
C
H
H
C
C
H
H
30
H
C
C
H
H
2. The data in Table 1 indicate that the Bps of organic compounds with
similar structures increase as the molecules increase in size.
H
H
H
1-hexene
C
H
H
C
H
H
C
H
H
63
C
C
H
H
C
H
H
H
H
1-heptene
C
H
H
C
H
H
C
C
H
H
C
H
H
94
H
C
C
H
H
H
H
H
1-octene
C
H
H
C
H
H
H
C
H
121
C
C
H
H
H
C
C
H
H
C
H
H
H
H
H
1-nonene
C
H
H
C
H
H
C
C
H
H
C
H
H
C
C
H
H
H
H
147
H
C
C
H
H
H
H
H
1-decene
C
H
H
C
C
H
H
H
C
C
H
H
H
C
C
H
H
C
H
H
H
C
C
H
H
H
H
171
3. The data in Table 1 indicate that the Bps of organic compounds with
similar structures that differ only in the number carbon and hydrogen
atoms increase as the molecules increase in size. This Bp trend is caused
by increases in intermolecular forces with increased molecular size.
4. The data in Table 1 indicate that the BPs of linear organic compounds
with similar structures that differ only in the number CH2 groups increase
as the molecules increase in size. This dependence is consistent with
changes in intermolecular forces in these compounds. The stronger the
intermolecular forces the more energy (higher Bp) is required to
overcome the forces and separate molecules in the liquid allowing them
to move to the gas phase. The primary intermolecular forces involved
with the non-polar molecules in Table 1 are London Forces, which are
due to the attraction of nuclei in one molecule for electrons on the surface
of another. So London Forces increase with increased surface area of the
molecules. Consequently, the boiling point increase comes from the
increased London Forces due to the additional molecular surface area
produced by each additional new CH2 group in the carbon chain.
H
Exploration:
1. Working as a group, make a list of the structural characteristics that are similar in all molecules in Table 1 of the Model.


Contain only carbon and hydrogen atoms in a continuous chain.
Contain 1 C-C double bond at the end of the chain.
Interpretation of Data
2
2. Working as a group, make a list of the structural characteristics that differ among the molecules in Table 1 of the Model.



Different number of carbon and hydrogen atoms (each successive compound has one additional CH 2 group in its chain).
Molecular weights are different as a result of the change in number of carbons and Hydrogen atoms.
Boiling points of the compounds are different (as the number of atoms increases, the molecular weight increases the Bp increases.
3. Read the 4 interpretations of the data presented in Model 1 and, working as a group, list them in order from strongest to weakest.
Strongest 4 > 3 > 2 > 1 Weakest
4. Working as a group, examine the elements of each interpretation and indicate how differences in these elements led your group to reach your
evaluation of the relative strengths of the interpretations.
Interpretation 1:
 Identifies a trend, but doesn’t provide any explanation for why the trend is attributed to molecular size.
Interpretation 2:
 Similar to Interpretation 1 but limits the application of the trend to “compounds with similar structures”.
Interpretation 3:
 Similar to Interpretation 2 but with additional qualifications “with similar structures that differ only in the number carbon and
hydrogen atoms “
 Some explanation “This Bp trend is caused by increases in intermolecular forces with increased molecular size.”
Interpretation 4:
 More qualification than the others “linear organic compounds with similar structures that differ only in the number CH2 groups”
 Explanation of how intermolecular forces affect Bp “The stronger the intermolecular forces the more energy (higher Bp) is required to
overcome the forces and separate molecules in the liquid allowing them to move to the gas phase.”
 Theory connecting strength of intermolecular forces to differences in the molecules, “The primary intermolecular forces involved
with the non-polar molecules in Table 1 are London Forces, which are due to the attraction of nuclei in one molecule for electrons on the
surface of another. So London Forces increase with increased surface area of the molecules. Consequently, the boiling point increase
comes from the increased London Forces due to the additional molecular surface area produced by each additional new CH2 group in the
carbon chain.
5. Working as a group, articulate one or more problems your group found with each interpretation. If possible suggest some additional data (not in
Table 1) that might address each problem your group identified.
Interpretation 1:
 All molecules in Table 1 have similar composition. The interpretation concludes that molecular size is the major factor in
determining bps. It extrapolates results from a limited data set to all organic molecules with no justification.
 Data on bps of molecules with different kinds of atoms but similar sizes to those in Table 1 would clarify if size is the most
important factor.
3
Interpretation of Data
Interpretation 2:
 Limits the application of the trend, but provides no explanation for the effect on Bp. The molecules vary in # of carbon atoms and #
of hydrogen atoms and length of the carbon chair. All three of these variables increase as the Bp increases. What was the logic that
led to choosing molecular size as the important variable?
 Data on bps of a few series of molecules with different kinds of atoms but similar trends in sizes to those in Table 1 would clarify if
size is the most important factor.
Interpretation 4: What is the basis for judging the molecules in Table 1 as non-polar?
Interpretation 3:
 Limits application of trend to a small set of molecules and provides a connection to forces that might determine Bps, but doesn’t
provide any explanation of how structure changes cause changes in intermolecular forces that could explain Bp trends.
 Rather than additional data, this interpretation needs a deeper discussion of the theory explaining how molecular structure affect
intermolecular forces and how the strengths of intermolecular forces affect bps.
Interpretation 4:
 Identifies the specific structural variable among the molecules and provides a theoretical basis for intermolecular forces changes
with structure variation. But provides no explanation as to the bases for judging the molecules in table 1 as non-polar.
 Rather than additional data, this interpretation needs a discussion of how molecular structure is related to molecular polarity.
Interpretation of Data
4
Toulmin Argumentation Model
(http://owlet.letu.edu/contenthtml/research/toulmin.html)
Stephen Toulmin developed a general model for rhetorical arguments*. Although it has been used primarily in law, his model is applicable to all forms of
persuasive rhetoric. Representations of two forms of his model are outlined below with definitions of terms used to identify key elements of arguments.
6. As a group examine the to Toulman models and then supply one example of each term from your analysis of interpretations 1-4 above.
* Here the term argument applies to a presentation of a point of view in an attempt to persuade someone.
Fundamental Elements
Data
(Evidence)
Claim
(Conclusion)
Warrant
(Explanation)
Term
Definition
Example
Claim (Conclusion):
A conclusion or point that is the focus of the
Bps increase with increased molecular size
argument.
Data (Grounds or Evidence):
The material offered to support the Claim.
Data in Table 1
Warrant (explanation)
Explains why or how the data supports the claim.
Bp trend is caused by increases in intermolecular forces
with increased molecular size
5
Interpretation of Data
Additional Elements
Qualifier
Data
(Evidence)
Claim
(Conclusion)
Warrant
(Explanation)
Backing
(Theory)
Term
Qualifier
Definition
Limitations on the Claim
Backing
Theoretical support for the Warrant
Rebuttal (counterpoint)
An exception to the claim.
Example
Linear organic compounds with similar structures that
differ only in the number CH2 groups
The primary intermolecular forces involved with the nonpolar molecules in Table 1 are London Forces, which are
due to the attraction of nuclei in one molecule for
electrons on the surface of another. So London Forces
increase with increased surface area of the molecules.
Consequently, the boiling point increase comes from the
increased London Forces due to the additional molecular
surface area produced by each additional new CH2 group
in the carbon chain.
See responses to 5. below: It extrapolates results from a
limited data set to all organic molecules with no
justification.
7. Circle or highlight and label any Claims, Data, Warrants, Backing, Qualifiers and Rebuttals that may be present in each of the four interpretations in
the Model.
See Highlights in the Model: Claims, Data, Qualifier, Warrant, Backing and Rebuttal
8. Reconsider the order of strengths of the interpretations you proposed in 3. Explain your final order using your Toulmin Analysis in 7.
Should now conclude the order to be 4 > 3 > 2 > 1 based on the elements of the Toulmin Model present in each.
Interpretation of Data
6
Application:
1. As a group, consider each of the following “arguments” using the Toulmin Argumentation Model devised in this activity. Circle and label the
Claims, Data, Warrants, Backing, Qualifiers and Rebuttals that may be present in each “argument” and briefly explain how your group
recognized each element (Provide data and a warrant to support each claim in your explanation.)
Color code: Claims, Data, Qualifier, Warrant, Backing and Rebuttal
a. Sarah addressing her parents: “Nearly all of my classmates’ parents are allowing them to go to John’s party on Saturday night. So you should
allow me to go. You know most of the parents, so you should accept their judgments. Besides, John has had three parties in the last year and
there were no problems at any of them.” (Adapted from www.uhseport.net/published/j/gl/jglass/.../upload.c-jglass-6n32.ppt)
b. A fourth-grade class has been asked to find the area of a 4 X 7 rectangle.
During the discussion, Jane states: “The answer is 28. I got it by multiplying the length times the width; that is how you get the area of a
rectangle.” John replies: “I see where you get 28 now, but why do you multiply 4 by 7 to get 28?” Jane replies by drawing a series of 1 X 1
squares to fill the rectangle and saying, “You see, you have 4 rows of 7 squares each with an area of 1. That’s why you can multiply 4 by 7 to
get the area.” (Adapted from “A methodology for documenting collective activity”, Chris Rasmussen and Michelle Stephan)
c. A prosecutor’s closing argument in a court case: “Wilkenson has committed an offense against the Road Traffic Acts. Two policemen have
testified that that they clocked him at 45 mph in a residential area. Since the Road Traffic Acts set the maximum speed in that area as 30
mph, he is guilty of an offense against the those acts. (Adapted from The Uses of Argument, by Stephen Toulmin)
7
Interpretation of Data
2. As a group, reconsider the rebuttals you proposed in item 6. of the Exploration and identify any Claims, Data, Warrants, Backing, Qualifiers and
Rebuttals that may be present in each. Finally strengthen the rebuttals by adding additional elements that are missing. Include your strengthened
rebuttals below.
Interpretation 1:
Original Rebuttal: It extrapolates results from a limited data set to all organic molecules with no justification. Claim only
Add
Data: The molecules in Table 1 contain only carbon and hydrogen atoms. Many organic molecules contain other kinds of atoms and contain
different kinds of bonds.
Warrant: To apply the claim in Interpretation 1 to all organic compounds would require data on boiling point data from molecules with a
variety of kinds of atoms and different bonding structures.
Interpretation 2:
Original Rebuttal: The molecules vary in # of carbon atoms and # of hydrogen atoms and length of the carbon chair. All three of these
variables increase as the Bp increases. What was the logic that led to choosing molecular size as the important
variable? Data and Claim.
Add
Revised Claim: Cannot choose only one variable without justifying the choice.
Warrant: Correlation between two variables does not indicate causality.
Backing: To be sure of a causal relationship one must explore data with only one independent variable (structural) and one dependent
variable (experimental measurement).
Interpretation 3:
Original Rebuttal: It doesn’t provide any explanation of how structure changes cause changes in intermolecular forces that could
explain Bp trends. Data Only
Add
Claim: An effective argument for this structure function relationship must provide a connection between structural changes and changes in
intermolecular forces.
Revised Data: The above connection is missing in Interpretation 3.
Warrant: It is not possible to understand the logic that led to this interpretation without theory to link structure changes to changes in
intermolecular forces.
Backing: Memorizing the relationship between a trend in structural change and an observe characteristic is useful only for the data set under
study. Connecting the observed situation to a general concept allows it to be applied to a variety of different situations.
Interpretation 4:
Original Rebuttal: It provides no explanation as to the bases for judging the molecules in table 1 as non-polar.. . . this interpretation
needs a discussion of how molecular structure is related to molecular polarity.
Add
Warrant: This claim depends on the understanding of how the bonding pattern in the molecules in Table 1 lead to the molecules being nonpolar.
Backing: As with Interpretation 4, Memorizing the relationship between a trend in structural change and an observe characteristic is useful
only for the data set under study. Connecting the observed situation to a general concept allows it to be applied to a variety of different
situations.
Interpretation of Data
8
3. Using the data in Table 2, respond to the following:
Table 2
C6H12O
A
C5H12O
B
What do formulas A & B have in common? Could they represent the same molecule? Explain identifying the elements of the Toulmin Argumentation
Model that are in your response.
Data: From Table 2, A & B are both comprised of carbon, hydrogen and oxygen atoms and have the same number of Hydrogen atoms and the same
number of oxygen atoms. They differ in the number of carbon atoms.
Claim: A & B could not represent the same molecule.
Warrant: The two formulas have different numbers of carbon atoms.
Backing: Molecules have a definite number of atoms of each kind, molecular formula.