Communication pubs.acs.org/jchemeduc
Mole Pi: Using New Technology To Teach the Magnitude of a Mole Michael J. Geyer* Sycamore High School, Cincinnati, Ohio 45242, United States S Supporting Information *
ABSTRACT: A modified technique for demonstrating the magnitude of Avogadro’s number using a new Raspberry Pi computer and the Python language is described. The technique also provides students the opportunity to review dimensional analysis. KEYWORDS: High School/Introductory Chemistry, Stoichiometry, Analogies/Transfer are approaching and reached. Within the first month I formally perform the calculation that shows my students that this number will not be reached for trillions of years (at least with the computers I’ve always used). I always get reactions of astonishment and disbelief. On one occasion I had a student come back to my classroom later in the day and interrupt my class to tell me that even if the computer had begun counting on the day the universe came into existence, it still would not have reached a mole by that day! By revisiting the computer’s progress and asking the students to perform the same detailed calculation later in the year we have also found that it does not count at the same rate continuously, but rather tends to slow down as the year progresses. The interest generated by our computer throughout the entire year even extends beyond the chemistry classroom. Occasionally I have found students who, having heard about it, after school have time before some extracurricular activity, and check in on its progress. Tweets sent out over breaks also generate interest, and help renew curiosity on the first day back to school. As of this past school year, the highest I have ever been able to get our computer to count is 5.2 billion, not even the population of the earth. (A photo of the setup of our computer from the 2013−2014 school year is available in the Supporting Information.)
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arious methods for demonstrating the magnitude of a mole either by performing calculations and possibly comparing sizes of real-world objects imaginatively or by displaying the number in its integer form on the classroom wall using a banner are available for use in the classroom and have been reported at various times in this Journal.1−4 But making the size of this number tangible for students seems to be difficult even with these ideas. One method with which I have found some additional success is through the use of a computer program that counts by ones as fast as it can.5,6 I have used an old computer that has been repurposed and can run the program from its OS command line. When I first began using this method,6 I created my own program in Quick Basic, compiled it into an executable file (avogadro.exe), and saved it on a 3.5 in. diskette.
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USING THE COMPUTER PROGRAM IN A LESSON During the lesson in which I teach about the mole, I take a few minutes to use this method to attempt to convey its magnitude. Once the program is initiated I read to the class the rapid progression of the count over a 1 min time frame, attempting to emphasize just how fast the computer is counting. I then offer a challenge to my students, awarding a large amount of bonus points to the person who can guess the date on which the computer will reach a mole. Nearly all of my students turn in their guesses, and those are always within the current school year, mostly being a date less than a month away. Occasionally I get a student who has truly internalized the process of dimensional analysis and will tell me that it will not happen in our lifetime, with the math to prove it. I try to quiet those students quickly so as to maintain the educational impact of this exercise. The program then runs for the duration of the class time and gets stopped so I can repeat this process for each class of the day. When I get to my last class for the day, we position the computer in a highly visible area of our room (or department, depending on the school in which I am teaching), record the actual start time, and let it run. I will let it run for the duration of the entire school year, with the only thing stopping it being an unfortunate power outage or custodial electrical work. By letting the computer run continuously I can come back to it as time permits. The students routinely check on our computer (we name it and make reference to it in class), and I even send out tweets on my school Twitter account as major milestones © XXXX American Chemical Society and Division of Chemical Education, Inc.
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AVAILABLE NEW TECHNOLOGY I have always used donated computers (until they stopped working). However, because I was at the mercy of donations and old technology (computers with the appropriate drives and ports), there were a few years that I was unable to use this lesson. This past year, after having to quickly remove a leaking laptop battery from our current repurposed computer to prevent a serious problem, I was reminded of a gift I had received. I had heard of the Raspberry Pi computer7 created by the Raspberry Pi Foundation and had one I was tinkering with at home. This “low cost, credit-card sized computer” is “capable of doing everything you’d expect a desktop computer to do.” The cost for the model A is $25 and the B or B+ is $35, each well within the budget of a zealous chemistry teacher. With this very affordable computer I am no longer at the mercy of a generous donor or our school’s technology department. Nor do
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dx.doi.org/10.1021/ed500469w | J. Chem. Educ. XXXX, XXX, XXX−XXX
Journal of Chemical Education
Communication
I have to scramble to try to get my old Quick Basic program on to the computer using several different software transfers from one storage device to another. The Raspberry Pi is capable of accessing a LAN using an Ethernet cable (model B or B+) or Wi-Fi (all three models with a Wi-Fi dongle).
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UPDATED COMPUTER PROGRAM Having a background that included computer programming, I have used my Raspberry Pi to create a new version of the counting program in the Python programming language (Avogadro_3.py, available in the Supporting Information) which has a few new features for the classroom teacher and can run very easily on a Raspberry Pi. Like its predecessor, it counts by ones. Moreover, when finished it will display the start date and time as well as the ending date and time. In addition I have added the actual count time between these two points. I have also added an input so that the teacher can include the final count value, which will make it very useful on the first day of the lesson. This year I will be able to input one or more values during that first class and allow the Pi to successfully reach that count (e.g., 50,000 or 602,000). We can record the actual time needed to count to these values and refer back to them when I perform a detailed calculation showing just how long it will take. I can then restart Avogadro_3.py, input 6.02e23, and let it begin. In my initial trials I have also noticed that the Raspberry Pi has shaved about 1000 years off of the time I have previously needed with my old computers. I can bring this up to my class with a straight face and see what kind of response I’ll get. Humor never hurts.
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ASSOCIATED CONTENT
S Supporting Information *
Avogadro_3py.txt (Python 3 code in text format for modifying); photograph of 2013−2014 computer setup. This material is available via the Internet at http://pubs.acs.org.
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AUTHOR INFORMATION
Corresponding Author
*E-mail:
[email protected]. Notes
The authors declare no competing financial interest.
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REFERENCES
(1) Poskozim, P. S.; Wazorick, J. W.; Tiempetpaisal, P.; Joyce, A. P. Analogies for Avogadro’s Number. J. Chem. Educ. 1986, 63, 125. (2) Godshall, C. J.; Herrick, J.; vander Water, K.; Bogner, D. (1987). “Million” Ideas. J. Chem. Educ. . 1987, 64, 956. (3) Tannenbaum, I. R. How Large Is a Mole? J. Chem. Educ. 1990, 67, 481. (4) Uthe, R. E. For Mole Problems, Call Avogadro: 602-1023. J. Chem. Educ. 2002, 79, 1213. (5) Koven, B. A. A “Real Time” Footnote to “Million Ideas”. J. Chem. Educ. 1989, 66, 829. (6) Toloudis, M. The Size of a Mole. J. Chem. Educ. 1996, 73, 348. (7) Raspberry Pi Foundation. http://www.raspberrypi.org/ (accessed Sep 2014).
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