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 Im 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, lets 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
"I think that the point Im 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
thats something that a lot of students dont
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
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.
to Unit 3.4