How does nature know which way is forward?
Initial Publication Date: August 19, 2008
Summary
Examination of Second of Thermodynamics (endo/exothermic and entropy) using a thought story, rubber band inquiry, discrepant event and lecture.
CollapseLearning Goals
Through critical thinking, students realize that spontaneous events happen in a certain order.
Synthesizing ideas allows students to recognize "something else" (other than heat) determines the directions of a reaction.
Synthesizing ideas allows students to recognize "something else" (other than heat) determines the directions of a reaction.
Vocabulary:
-Enthalpy
-Entropy
-Spontaneity
-Free Energy
Context for Use
This lesson would be most appropriate for honors level chemistry courses.
Prior to the activity, students must be familar with endo and exothermic reactions (enthalpy). In addition, a discussion of the first law of thermodynamics would be helpful.
The activity is used as an introduction to the second law of thermodynamics.
Prior to the activity, students must be familar with endo and exothermic reactions (enthalpy). In addition, a discussion of the first law of thermodynamics would be helpful.
The activity is used as an introduction to the second law of thermodynamics.
Description and Teaching Materials
First, students are asked to silently read and reflect on the Alien Story.
Teacher reads some of the creative answers to spark a discussion around what "drives" nature.
Then, the rubber band activity is presented.
Here, students observe spontaneous and nonspontaneous processes, collecting data on the heat exchange. The conclusion is drawn that all spontaneous reactions are NOT exothermic.
Following this, a lecture on second law ensues on SMARTBoard.
On a following day, the second law is "violated" using the anti-entropy device....laminar flow using corn syrup and dye. In one direction the dye appears to spread, twisting the device backwards the dye gets ordered. Students are questioned on how it is possible for the dye to "spontaneously" organize. (Answer: Instuctor's body is doing work on the system, thereby creating disorder from burning food; in this case, the disorder in the work performed offsets the order restored in the dye).
More lecture to lead into derivation of Gibb's Free Energy equation. Alien Story (Microsoft Word 40kB Aug19 08) Rubber Band Activity (Microsoft Word 26kB Aug19 08) Lecture Notes - PDF (Acrobat (PDF) 538kB Aug19 08)
Teacher reads some of the creative answers to spark a discussion around what "drives" nature.
Then, the rubber band activity is presented.
Here, students observe spontaneous and nonspontaneous processes, collecting data on the heat exchange. The conclusion is drawn that all spontaneous reactions are NOT exothermic.
Following this, a lecture on second law ensues on SMARTBoard.
On a following day, the second law is "violated" using the anti-entropy device....laminar flow using corn syrup and dye. In one direction the dye appears to spread, twisting the device backwards the dye gets ordered. Students are questioned on how it is possible for the dye to "spontaneously" organize. (Answer: Instuctor's body is doing work on the system, thereby creating disorder from burning food; in this case, the disorder in the work performed offsets the order restored in the dye).
More lecture to lead into derivation of Gibb's Free Energy equation. Alien Story (Microsoft Word 40kB Aug19 08) Rubber Band Activity (Microsoft Word 26kB Aug19 08) Lecture Notes - PDF (Acrobat (PDF) 538kB Aug19 08)
Teaching Notes and Tips
This lesson is written for second year chemistry students. Or, gifted first year students.
Here's a site on how the anti-entropy device is construted:
http://www.fas.harvard.edu/~scidemos/NewtonianMechanics/ReversibleFluidMixing/ReversibleFluidMixing.html
Here's a site on how the anti-entropy device is construted:
http://www.fas.harvard.edu/~scidemos/NewtonianMechanics/ReversibleFluidMixing/ReversibleFluidMixing.html
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Assessment
End of unit exam.
A favorited essay question for the exam...
True or False. According to the second law of thermodynamics, a crystal will never form spontaneously because it is more ordered than the particles it is made from. Explain.
A favorited essay question for the exam...
True or False. According to the second law of thermodynamics, a crystal will never form spontaneously because it is more ordered than the particles it is made from. Explain.
Standards
To my knowledge, the state standards do not speak to the second law of thermodynamics.