Teacher resources and professional development across the curriculum

Teacher professional development and classroom resources across the curriculum

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Reactions in Chemistry
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Sub Image2:Macro to Micro Structures
1) Atoms and Molecules2) Macro to Micro Structures 3) Energetics and Dynamics
4) Theory and Practice in Chemical Systems5) Chemical Design6) The Chemistry of Life7) Chemistry and the Environment8) Chemistry at the Interface

Unit 3.3 The Dynamics of a Reaction
In this unit we see ways to illustrate the concept of reaction rate, either by simulating the molecular level processes or by relating reaction rates and the factors that affect the rates.
Video program cues: 10:50 — 21:30.

Animating NaCl Crystals

"Take, for example, a very simple reaction: adding water to salt which is dissolving. What you see is macro level: first you see crystals, then you stir it up. After a while the crystals disappear and you only see a clear liquid. What I’m asking you now is to imagine that you go down to the surface of one of these crystals. What would you see, what would you imagine, as the water molecules come down, let’s just talk about what is happening in this dissolving process. What is up here, for example, is a crystal of sodium chloride; the green spheres represent the chloride ions, whereas the bright spheres represent the sodium ions. As I start the animation, they start vibrating and moving. Now the water molecules are surrounding the chloride ions as piranhas eating a piece of meat and pull the chloride ion out, and then they surround S ions and pull them out. You notice that there is a bit of competition."

"I think that the point I’m trying to make is that in an animation like this you can get a number of key features across, one of them being that, now the ions of the sodium chloride are vibrating, moving. Now that’s something that a lot of students don’t really appreciate because they think that if something is a solid that everything inside must be still, but they are actually always moving. The ions are of course always jiggling around, and melting is when you add heat, the ions move and vibrate until suddenly the whole structure just breaks down, and that is actually what melting is."

Dr. Roy Tasker
Associate Professor, Univ. of Western Sydney


  • A computer simulation of dissolving salt similar to the one Dr. Tasker shows in the video
Burke, K. A.; Greenbowe, T. J.; Windschitl, M. A. (1998)' Developing and Using Conceptual Computer Animations for Chemistry Instruction, 'Journal of Chemical Education, Vol. 75, No. 12, pp: 1658.

Sanger, M.J.; Phelps, A.J.; Fienhold, J. (2000)' Using a Computer Animation to Improve Students' Conceptual Understanding of a Can-Crushing Demonstration, 'Journal of Chemical Education, Vol. 77, No. 11, pp: 1517-1520.

Liberko, Charles A.; Terry, Stephanie.(2001)' A Simplified Method for Measuring the Entropy Change of Urea Dissolution. An Experiment for the Introductory Chemistry Lab, 'Journal of Chemical Education, Vol. 78, No. 8, pp: 1087.

Reaction Rates Demonstration and Laboratory

Irene Walsh demonstrates the effect of concentration on reaction rate through clock reactions in the laboratory.



Bowers, P.G.; Rubin, M.B.; Noyes, R.M.; Andueza, D. (1997)' Carbon Dioxide Dissolution as a Relaxation Process: A Kinetics Experiment for Physical Chemistry, 'Journal of Chemical Education, Vol. 74, No. 12, pp: 1455.

Creary, X.; Morris, K. M. (1999)' A New Twist on the Iodine Clock Reaction: Determining the Order of a Reaction, 'Journal of Chemical Education, Vol. 76, No. 4, pp: 530.

Proceed to Unit 3.4 arrow

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