In the Classroom
Thermodynamics in Context A Case Study of Contextualized Teaching for Undergraduates John Holman* and Gwen Pilling Department of Chemistry, University of York, York YO10 5DD, United Kingdom; *
[email protected] Chemical thermodynamics is often considered abstract and conceptually demanding, though in reality it provides profound insights to the workings of the universe. We were interested to know if this fascinating subject could be made more accessible by taking a contextualized approach. Context-led approaches, whereby relevant applications are used as the starting point from which to develop chemical concepts, have become common at high school level. ChemCom (1) is well known in the United States, and Salters Advanced Chemistry (2), a pre-university course, has been widely adopted in the United Kingdom and adapted for use in Germany, Russia, Spain, and Sweden. We have, at different times, directed the project that produced the Salters Advanced Chemistry teaching materials and taught and examined this course at the high school level, so we were interested to know whether the approach could be extended to undergraduate study at the university level. Chemistry in Context (3) provides a context-led approach to chemistry for nonscience majors at the university level, but would the approach work for science majors at the university level? An opportunity to find out arose when one of us joined the Chemistry Department at the University of York in 2000 and discovered he had been allocated first-year thermodynamics teaching. Working with Michael Pilling of the University of Leeds (who also teaches first-year thermodynamics) we set out to design a short course for chemistry majors dealing with gas laws and the first law of thermodynamics. The original course comprised ten, one-hour lectures; one, one-hour tutorial; and one, one-hour workshop. The new course was designed to fit into the same framework. The main problems with the existing course were diagnosed as follows: i. It was dry and theoretical, which makes it hard for students to see its relevance to real life or to their other studies. ii. It was difficult for students who do not have a strong mathematical background. iii. The traditional approach to teaching thermodynamics did not take full account of students’ prior conceptions.
Contexts for the Thermodynamics Course To deal with the first of the problems identified above, we have produced a contextualized approach to thermodynamics. We decided on an ‘infusion’ approach (4), whereby contexts are inserted into the existing course, rather than a more radical context-led approach in which a completely new course would be written with contexts as starting points, in the manner of ChemCom or Salters. We were aware that appropriate contexts are age-dependent (5) and we identified a www.JCE.DivCHED.org
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variety of contexts, including personal (for example, the energy value of foods), social, environmental (environmental impact of fuels), technological (car airbags), and researchlinked (the actin–myosin molecular motor). Research-linked contexts, we felt, were particularly appropriate for a university-level course. We drew on many sources for contexts, including ChemConnections (6, 7). Contexts were applied to the course in the following ways. Lecture snippets: These are short contextual insertions in the lecture course; for example, there is a snippet on whole-body calorimetry. Table 1 summarizes the lecture course and shows these infusions. Contextualized tutorial problems: In British universities, tutorials are intensive small group sessions in which students answer pre-assigned problems. An example of a contextualized tutorial problem is “The energy value of beer.” Workshop problems: Workshops are large group problemsolving sessions. An example of contextualized workshop problem is “Why does it get hot in the stratosphere?” Assessment questions: Contextualized questions were devised to assess students in their end-of-module examination. For example, one question used the context of liquefied natural gas as a replacement for gasoline.
Short demonstrations and video-clips were used in lectures as a different kind of context. The enduring appeal of chemical demonstrations is well known, and the advantage of thermodynamics is that it is relevant to any chemical reaction the instructor cares to demonstrate. A spectacular favorite, the catalytic oxidation of ammonia (8), provides a striking context for discussing enthalpy change and expansion work. To provide support for students with limited mathematical skills, we devised the Energetics Question Bank—a bank of Web-based questions that could be accessed by students from any computer in the university. The questions provide practice and walkthrough answers to straightforward gas and thermodynamics problems, and give particular help with getting the units right. There is no attempt to place these problems in context: they are designed to provide practice in a simple, no-frills way. Many instructors (9) have called for a “constructivist” approach to teaching science. In Ausubel’s words, The most important single factor influencing learning is what the learner already knows. Ascertain this and teach accordingly. (10)
For university instructors, not necessarily familiar with what is taught in high school, this is not always easy to do. In their study of the thermodynamics understanding by first-year un-
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dergraduates, Carson and Watson (11) highlight the problem of a mismatch between students’ prior understanding of energy and the treatment of enthalpy and internal energy that they encounter at university. A particular difficulty exists with the order in which the students are taught. Standard texts (12) deal with internal energy first, then proceed to discuss the heat transferred and work, treating enthalpy change as a particular case of heat change at constant pressure. This fundamental approach is logical to those who are intimate with the subject, but not to students fresh from studying enthalpy change at high school. We decided to reverse the order and deal with enthalpy change and constant pressure calorimetry before proceeding to internal energy change and linking it to bond energies and molecular motion. Results The new approach has now been tested with a group of 95 students at the University of York in October 2001 and with 125 students at the University of Leeds in February
2002. In Leeds, the approach was incorporated into a longer course on thermodynamics, some of which was still taught in a traditional way. This made evaluation difficult for this session, particularly as the instructor had changed from the previous year. To evaluate the new course at York, an end-of-course questionnaire was administered, consisting of questions answered on a 1-to-5 scale. An identical questionnaire had been used with the group of students taught by the same instructor the previous year. This made a comparison between the new and the old approach possible. The results have to be treated with caution because the two groups of students were different, but the average intake grades of the two groups differed by less than 2%, suggesting that they were comparable. Some results from the questionnaire are presented in Table 2. The results suggest that the new approach did a better job in making thermodynamics interesting and the principles clear. There is some suggestion that the students found the pace of the new course more challenging; this may be due to the extra time needed to include the contextual material.
Table 1. Gases and the First Law of Thermodynamics: Course Outline 2001 Chemistry
Context
Gases 1. Quantities and units
Design an airbag system
2. Perfect gas equation of state
Airbags: how much?
3. Partial pressures 4. Kinetic theory and the gas law 5. Speeds of molecules 6. Effusion and diffusion 7. Collisions between molecules
Vacuum pumps: do they really suck?
8. van der Waals equation of state 9. Liquefaction
Supercritical carbon dioxide: a better way to get flavor from hops
Energetics: Useful Concepts 10. System and surroundings
Space stations: closed systems
11. State functions Thermochemistry 12. Standard states 13. Enthalpy changes
Does hot water freeze faster than cold?
14. Heat capacity
Whole-body calorimetry
15. Useful enthalpy changes
How to make fuel taxes green
16. Using Hess’s law
Energy from ATP; Is beer fattening?
17. Bond enthalpies and bond dissociation energies
What happens in a flame?
18. Change of ∆H with temperature First Law of Thermodynamics 19. Work and heat
Nitroglycerine: the inside story
20. Reversible and irreversible changes
Airbags: how much heat? How much work?
21. Internal energy changes
Oxidation of glucose in biological systems
22. First law of thermodynamics 23. Enthalpy and internal energy 24. Molar heat capacities: Cp and Cv
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What if the sea were made of ethanol?
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In addition to the questionnaire, a focus group discussion was held with seven students who had just completed the new course. Positive comments from this group can be summarized as: • • •
Table 2. Average Scoresa from Student Questionnaire Resultsb 2000c
Question
2001
In general, students found the course interesting and relevant.
Lecturer stimulated interest?
2.92
3.60
Lecturer made principles clear?
3.92
4.21
Demonstrations were very popular.
Lecturer developed ideas at right pace?
3.80
3.75
Computerized question bank was popular.
Lecturer interacted effectively?
3.84
4.18
Lecturer left enough time for taking notes?
4.18
3.97
Negative comments can be summarized as:
a
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Tutorial questions were considered hard.
•
Treatment of gases assumed too much prior knowledge from high school.
The perceived difficulty of the contextualized tutorial questions is interesting. Experience with Salters Advanced Chemistry at high school suggests that while contextualization makes learning more accessible, it can make problem-solving more difficult. This can be attributed to the well-known difficulty of solving problems in unfamiliar contexts. A final piece of evaluative evidence is provided by the examination performance of the York students. In 2000, the group of 114 students who were taught with the old approach scored an average 48.5% in the thermodynamics part of the end-of-module examination; in 2001, those who followed the new approach scored an average 61.3%. This evidence is of limited value because the examination questions were different, although the department’s examinations committee moderated their standard. Nevertheless, it does suggest that this contextualized approach improves learning at the same time as increasing interest. Summary We are encouraged by the results of the new approach and believe it provides a formula for increasing the interest of a traditionally dry subject without sacrificing rigor or quality of learning. We have now produced a similar contextualized approach to the second law of thermodynamics, which was first taught in 2003. We hope to be able to report further results in the future, including a more rigorous evaluation of the new approach from both universities where the course was used. Meanwhile we would like to hear from others who are interested in bringing the benefits of contextualized teaching to undergraduate chemistry. The lecture handouts, tutorial and workshop problems, examination questions and computerized question bank de-
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Averages of scores on a 1 to 5 scale; 1 worst, 5 best.
b
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In 2000 the traditional approach was used; in 2001 the new approach was used. c
Number of students in 2000 was 114 and in 2001 was 95.
scribed in this article can be found at http://www.physsci. ltsn.ac.uk/devprojs/reports/thermo.htm (accessed Nov 2003). Literature Cited 1. ChemCom: Chemistry in the Community, 4th ed.; Heikinnen, H., Ed.; W. H. Freeman: New York, 2002. 2. Burton, W.; Holman, J.; Pilling, G.; Waddington, D. Salters Advanced Chemistry; Heinemann: Oxford, 1994 and 2000. 3. Stanitski, C. L.; Eubanks, L. P.; Middlecamp, C. H.; Stratton, W. J. Chemistry in Context, 3rd ed.; McGraw Hill: Boston, 2000. 4. Aikenhead, G. What is STS Teaching? In STS Education: International Perspectives on Reform; Solomon, J., Aikenhead, G., Eds.; Teachers College Press: New York, 1994. 5. Bennett, J.; Holman, J. In Chemical Education: Towards Research-based Practice; Gilbert, J., Ed.; Wouters-Kluwer: Dordrecht, The Netherlands, 2002. 6. ChemConnections Home Page, Beloit College, 2003. http:// chemistry.beloit.edu (accessed Nov, 2003). 7. Gutwill-Wise, J. J. Chem. Educ. 2001, 78, 684–690. 8. Volkovich, V. A.; Griffiths, T. R. J. Chem. Educ. 2000, 77, 177. 9. For example, Driver, R. A Constructivist Approach to Curriculum Development. In Development and Dilemmas in Science Education; Fensham, P., Ed.; Falmer Press: London, 1988; pp 133–149. 10. Ausubel, D. P. Educational Psychology. A Cognitive View; Holt, Rinehart & Winston: New York, 1968. 11. Carson, E.; Watson, J. Uni. Chem. Educ. 1999, 3, 46–51. 12. Atkins, P. The Elements of Physical Chemistry, 3rd ed.; Oxford University Press: Oxford, 2001.
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