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Why Don't Things Go Wrong More Often? Activation Energies: Maxwell's Angels, Obstacles to Murphy's Law

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Frank L. Lambert

2834 Lewis Dr., La Verne, CA 91750

J. Chem. Educ., 1997, 74 (8), p 947

DOI: 10.1021/ed074p947

Publication Date (Web): August 1, 1997

Abstract

Students often invoke Murphy's Law when inanimate "things go wrong", when skis break or fires occur or instruments fail due to corrosion or tires unexpectedly wear out. But why don't similar upsetting events happen to everyone every minute? Unwanted combustion and corrosion of common materials, although energetically favored, are not kinetically instantaneous. (The second law of thermodynamics is time's arrow but chemical kinetics is time's clock.) Chemistry students learn that chemical changes are usually obstructed by activation energy barriers whose origins lie in the energy required for bond breaking as new bonds are formed. Thus, activation energies act as obstacles to Murphy's Law in being deterrents to undesirable reactions and, lightly, as our "Maxwell's Angels". The fracture of solids - whether surfboards or car fenders - also involves breaking chemical bonds. However, such incidents are classed as physical changes because the free energy of the fragments is not notably different from the unbroken whole. The micro-complexity of fracturing utilitarian or beautiful objects prevents assigning a characteristic activation energy even to chemically identical artifacts. Nevertheless, a qualitative EACT SOLID can be developed. Its surmounting is correlated with the radical drop in human valuation of an object when it is broken.

Keywords (Audience):

High School / Introductory Chemistry

Keywords (Domain):

Physical Chemistry

Keywords (Pedagogy):

Analogies / Transfer

Keywords (Subject):

Kinetics

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This article has been cited by 1 ACS Journal articles (1 most recent appear below).

Entropy Is Simple, Qualitatively
Frank L. Lambert
Journal of Chemical Education2002 79 (10), 1241
- Entropy Is Simple, Qualitatively
  Frank L. Lambert
  Journal of Chemical Education2002 79 (10), 1241
  Qualitatively, entropy is simple. What it is, why it is useful in understanding the behavior of macro systems or of molecular systems is easy to state: Entropy increase from a macro viewpoint is a measure of the dispersal of energy from localized to ...
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