University of Wisconsin-Stevens Point
Assessing Critical Thinking from Course to Campus
Assessing Critical Thinking in Fundamental Chemistry: Justifying Conclusions with Observations
Steve Wright, Chemistry Department, UW-SP
Joanne Kurfiss defines critical thinking as “an investigation whose purpose is to explore a
situation, phenomenon, question, or problem to arrive at a hypothesis or conclusion about it that
integrates all available information and that can therefore be convincingly justified.”1 Kurfiss
contends that chemists (natural scientists) draw reasonable inferences from observation and
evaluate findings to generate new questions or experiments. Summarizing, critical thinking in
natural sciences includes:
•
•
Justifying conclusion (hypotheses) with observation, and
Expanding the scope of those hypotheses with further observation.
Learning Outcomes – Chemistry 105
• Use and critique the scientific method as a process to develop theoretical constructs
and/or solve problems.
• Consider reasonable data/observations to draw justifiable conclusions and make informed
decisions.
• Use abstract concepts to develop well-reasoned solutions to problems.
• Communicate convincingly when proposing solutions to problems or explaining
observations.
• Select and apply appropriate theories of chemistry to explain phenomena.
Some Classroom Strategies
• POGIL (Process Oriented Guided-Inquiry Learning)
http://www.pogil.org/
• Case Studies
http://ublib.buffalo.edu/libraries/projects/cases/case.html
• Baffled by the Baby Bottle
• PCB’s in the Last Frontier: A Case Study on the Scientific Method
• Data-Driven Approach
http://www.uwsp.edu/chemistry/chemproj/fipse/index.htm
• Student Survival Guide
• Worksheets for Chemistry 105
• Class research project
Uptake of metals in plants
Assessing Critical Thinking in Fundamental Chemistry
• Worksheets
• Laboratory
• Exam
• Quizzes
• New Thing to Try – (Certain) Case Studies
• http://www.sciencecases.org/last_frontier/last_frontier.asp
1
Kurfiss, Joanne G. Critical Thinking: Theory, Research, Practice, and Possibilities. ASHE-ERIC Higher
Education Report No. 2. Washington, K.C.: The George Washington University, Graduate School of
Education and Human Development.
Assessment Ideas
In Class
Homework
Exams
Papers
Other
Worksheet Example
Chapter Two
Caffeine Data
Consider the data concerning caffeine given to you. Determine the percentage of carbon,
hydrogen, nitrogen, and oxygen in caffeine from each of the beverage sources given on the data
table.
Table 1
Percentage of Carbon, Hydrogen, Nitrogen, and Oxygen Found in Caffeine Taken from
Various Sources
Source
Hot Cocoa
Decaf Coffee
Tea
Coca-Cola
Instant Coffee
Espresso Coffee
Brewed Coffee
% Carbon
% Hydrogen
% Nitrogen
% Oxygen
1. Compare these percentages to those you calculated previously using the distillation data
for Liquids One and Two. How are these percentages different (or similar) from the
percentages calculated for Liquids One and Two?
2. Now, consider all four liquids described on the distillation worksheet. Each of these
liquids is injected into a gas chromatography instrument. How many peaks would you
predict for each chromatogram?
Liquid
Liquid One
Liquid Two
Liquid Three
Liquid Four
Number of Chromatography Peaks
3. What determines the number of chromatography peaks observed?
4. A sample of caffeine is injected into a high performance liquid chromatography
instrument. How many peaks would you expect on the chromatogram? Explain.
When you are finished, your instructor will show you the chromatogram from a caffeine sample
to verify your prediction.
Table 2
Amount of Caffeine in 6 Ounce (about 160 mL) of Various Beverages
Beverage
Hot Cocoa
Decaf Coffee
Tea
Coca-Cola
Instant Coffee
Espresso Coffee
Brewed Coffee
mg of Caffeine
2-20
2-5
20-100
23
60-100
270-330
80-175
Table 3
Amount of Carbon, Hydrogen, Nitrogen, and Oxygen Obtained from Caffeine Taken from
Various Sources
Source
Hot Cocoa
Decaf Coffee
Tea
Coca-Cola
Instant Coffee
Espresso Coffee
Brewed Coffee
mg Carbon
4.95
1.97
24.73
11.37
39.59
148.4
61.84
mg Hydrogen
0.519
0.207
2.597
1.193
4.151
15.56
6.489
mg Nitrogen
2.89
1.15
14.41
6.637
23.07
86.56
36.05
mg Oxygen
1.65
0.657
8.243
3.793
13.17
49.44
20.61
Laboratory Example
The Case of the Corroding Cans
Adapted from a lab developed by J. Steehler et al at Roanoke College
A law-suit is brewing, and we’ve been asked to help. An unsuspecting buyer has purchased some land on
the Chain of Lakes near Eagle River for a family cottage. While walking the property, the buyer
discovered several large, partially full, corroding cans. Not knowing the contents of the cans and fearing
environmental contamination, the buyer did what any red-blooded American would do – he went straight to
his attorney. The buyer is suing the seller for the cost of removing all the barrels and testing the soil for
contamination, a total of $75,000. You have been hired by the court as a legal consultant to determine the
contents of the barrels and to give your opinion concerning their hazard. Your results will determine the
seller’s liability.
Several of the cans contain a deeply colored liquid. With some Internet searching, you’ve learned
that the seller (who was the previous owner of the property) manufactured and sold inks to three
different pen-manufacturing companies – Papermate, Pinpoint, and Vis-a-vis. Ink is a reasonable
first guess for these cans’ contents. The previous owner denies any knowledge of the cans, so
you will need to find some way to compare the inks found in Papermate, Pinpoint, and Vis-a-vis
pens to the colored liquids found in the corroding cans. This will help you determine whether the
cans’ contents are inks used by these companies.
Several other cans contain clear, colorless liquids. Although the cans are corroded, you can make
out the letters “HOL” on one can. Perhaps this is the end of the word “alcohol”. Unfortunately,
there are many types of alcohol, some considered toxic, some not as toxic. Methanol, ethanol,
and 2-propanol (also known as methyl alcohol, ethyl alcohol, and isopropyl alcohol) are the most
commonly used alcohols. These alcohols may have been used in the preparation of inks. You
will compare the colorless liquids in the cans to liquid samples of common alcohols in order to
identify the cans’ contents.
To identify these liquids, you will use chromatography, a technique that is often used to do
qualitative analysis on unknown samples. Qualitative analysis is any method used to determine
the identity of a substance. Your lab instructor will discuss this method with you. You will also
discuss chromatography as a method for separating mixtures.
After collecting your chromatographic data, you will write a report for the court. Your report
must follow the following format: purpose, brief procedure, data/observations, and conclusion.
Look in the previous paragraphs for hints on the purpose of the lab exercise. Briefly outline the
procedures you used - first paper chromatography, then gas chromatography. Carefully organize
and present your data so that the court is convinced of your first conclusion, the identity of the
liquids. Be sure to attach your chromatograms to your report.
Your conclusion must also include your recommendation concerning the property (Is the seller
liable for the clean-up?) and how you came to that recommendation. Consider some of the
following questions when making your recommendation2. Are the colored liquids found on the
property the inks sold to the pen-manufacturers? Are the colored liquids hazardous, making the
property unsafe? Does the buyer assume all responsibility, once the property is sold? To help
2
These questions are meant to help you discuss your recommendation. While some may be
appropriate to include in your conclusion, you do not have to address each question individually.
you with these questions, I’ve given you a list of LD50’s and PEL’s for the inks and some other
common substances. Use the “common” substances as reference points to determine the relative
hazard of the inks. I’ve given you definitions for some terms at the bottom of the page. Please
note that I made up the values for the inks. You will also be provided with Material Safety Data
Sheets for the alcohols. Use the MSDS’s to determine the potential hazards of the alcohols – and
make your recommendation based on that information. You may see abbreviations like UEL,
LEL, flash point, and/or autoignition temperature on the MSDS’s. These terms are also defined
below. Be sure to consider the hazards associated with the alcohols. Does the presence of the
alcohols make the property unacceptably risky? Who should be responsible for the clean up?
Lastly, remember that you are the court’s expert witness. Speculation and innuendo should not
be a part of your report. Base you recommendations only on data and observations.
Table of Toxicity Data
Substance
Sodium chloride (table salt)
Sucrose (table sugar)
Caffeine (in coffee)
Sodium cyanide (nasty poison)
Strychnine (nastier poison)
Papermate Ink5
Pinpoint Ink3
Vis-à-vis Ink3
LD503
3.75 g/kg (rats)
29.7 g/kg (rats)
0.13 g/kg (mice)
6 mg/kg (rats)
0.5 mg/kg
4.75 g/kg (mice)
80 mg/kg (rats)
2 mg/kg (rats)
PEL4
15 mg/m3 (nuisance particulate)
15 mg/m3 (nuisance particulate)
N/A
5 mg/m3
0.15 mg/m3
12 mg/m3
9 mg/m3
0.10 mg/m3
Some Useful Definitions for Reading MSDS’s
•
•
•
•
3
Flash Point – Lowest temperature at which a flammable liquid gives off sufficient vapor to
form an ignitable mixture with air near its surface.
Autoignition Temperature – Minimum temperature at which a substance ignites without
application of a flame or spark.
LEL – Lower Explosive Limit – The lowest concentration of a material in air (% by volume
in air) that produces an explosion when it contacts an ignition source.
UEL – Upper Explosive Limit – The highest concentration of a material in air (% by volume
in air) that produces an explosion when it contacts an ignition source.
LD50 is the lethal dose for half (50%) of a large population of animals. These values were taken
from The Extraordinary Chemistry of Ordinary Things and MSDS’s.
4
PEL is the Permissible Exposure Level for a substance. These are often given as 8-hour, time
weighted averages (TWA). These values have been taken from MSDS’s.
5
Remember, I’ve just made up the numbers for these “inks”.
Exam Questions (Examples)
Spring 2008; Chemistry 105 First Exam – 15% incorrect
A sample of matter is composed of different types of atoms held together by chemical bonds.
This sample is an example of
A. an element
B. a compound
C. an atom
D. a mixture
E. none of the above
Spring 2008; Chemistry 105 First Exam – 14% incorrect
A sample of matter cannot be decomposed chemically or separated by ordinary techniques. This
sample is most likely a(n)
A. element
B. compound
C. homogeneous mixture
D. heterogeneous mixture
E. none of the above.
Spring 2008; Chemistry 105 First Exam – 10% incorrect
The difference between separation and decomposition is
A. separation involves mixtures, while decomposition involves compounds.
B. separation involves the "breaking" of intermolecular forces (IMF's), while
decomposition involves the "breaking" of chemical bonds.
C. separation is relatively easy (low energy), while decomposition is relatively hard
(higher energy).
D. all of the above.
E. none of the above.
Spring 2008; Chemistry 105 First Exam – 30% incorrect
The compound chloroform, CHCl3, is injected into a gas chromatograph. The output of the GC
will show
A. three peaks, all of the same height.
B. three peaks, two of the same height, one of different height.
C. one peak.
D. five peaks, with three different heights.
E. the output of the GC cannot be determined from the information given.
Spring 2008; Chemistry 105 First Exam – Average on First Exam, 81%
You’ve found two bottles in the stockroom, each with its label missing. The sample from Bottle 1 boils at
100.1oC; the sample from Bottle 2 boils at 100.2oC. Careful analysis reveals the same two components in
each bottle – component A and component B. The mass of each component found in a sample taken from
each of the two bottles is given in the Table below. Determine whether the liquids in these bottles can be
combined into the same bottle? In other words, do these bottles contain the same pure substance? Briefly
explain. What further test might you run in order to verify your conclusion? (ten points)
Sample from Bottle 1
Sample from Bottle 2
Total Sample Mass (mg)
38.52 mg
47.64 mg
Mass Component A
0.3476 mg
0.7146 mg
Mass Component B
38.17 mg
46.93 mg
Spring 2008; Chemistry 105 First Exam – Average on First Exam, 81%
On the Table below you will find data from the distillation of a liquid sample. How many components are
in this sample? What are the weight/weight percents for each component? Show work. (ten points)
Distillation Data
Distilling a Total of 125.8 grams of Sample
Mass of the Distillate Collected (in grams)
Boiling Temperature (in degrees Celsius)
25.0 grams
56oC
30.0 grams
56oC
35.0 grams
56oC
40.0 grams
78oC
45.0 grams
78oC
50.0 grams
78oC
55.0 grams
78oC
60.0 grams
78oC
65.0 grams
78oC
70.0 grams
110oC
75.0 grams
110oC
Assume the rest of the sample boiled at essentially this same temperature: 110oC
Spring 2008; Chemistry 105 First Exam – Average on First Exam, 81%
Imagine that the box below is a syringe, loaded with a mixture of two compounds about to be injected into
a gas chromatograph. Using dots (•), circles (o), triangles (Δ), and diamonds (♦) as atoms and connecting
lines as chemical bonds, draw a molecular picture of this sample. Predict the output (number of peaks) of
the GC experiment and draw molecular pictures illustrating what the sample would look like after the GC
had been performed. Put your after GC picture(s) in a box(es). (Bear in mind what chromatography does.)
(ten points)
Spring 2008; Chemistry 105 Second Exam – 31% incorrect
Hypothetically speaking, can any amount of water be poured from one container to another?
A. Certainly, all you need is a very small (infinitely small) "eyedropper" to transfer extremely small
quantities of water.
B. Certainly, all you need is a very large (infinitely large) container to hold any amount of water.
C. Both A and B are correct, that is, you need both a very small (infinitely small) "eyedropper" and a
very large (infinitely large) container.
D. Of course not, you can only transfer water in multiples of 18 amu.
E. None of these make any sense.
Spring 2008; Chemistry 105 Final Exam – 31% incorrect
The compound dimethyl ether (C2H6O) is injected into a gas chromatograph. The output of the GC will
show
A. three peaks all of the same height.
B. three peaks, all of different height.
C. one peak.
D. nine peaks, with three different heights.
E. none of the above.