Teacher resources and professional development across the curriculum

Teacher professional development and classroom resources across the curriculum

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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 Systems 5) Chemical Design 6) The Chemistry of Life 7) Chemistry and the Environment 8) Chemistry at the Interface
From: Hauser, Michael (MHauser@stlcc.edu)
Date: Wed Feb 26 2003 - 12:44:33 EST

I had the opportunity this week to use the nuts and bolts analogy to
illustrate strong and weak acids and bases. After a bit of time, the
students figured it out. The real bonus came shortly thereafter when I
started explaining the structural characteristics that make acids strong or
weak. I showed a long bolt with the nut barely on AND a similar sized bolt
where the nut was wound way down onto the bolt.When I asked which bolt could
more easily "dissociate" the nut, they all answered correctly. NOW I was
ready to discuss dissociation as it relates to the electronegativity, size,
etc of the "non H" atom. Acids that hold on tightly to their H are weak
 A short while later we started pH. I used a measuring tape where I marked
off the log scale as shown on the video. I think I had been taking it for
granted that students understand what "logs" are besides a button they push
on the calculator.
It worked and I advise the use of one of the cloth measuring tapes that
winds up into a reel in a case. We marked the 1cm, 10 cm, 100cm and 1000 cm
areas with large paper clips as we unwound it. I was standing in the hallway
when we got to the 10 to the 3 power! Discussion of the Richter scale
difference between a "5" and a "6" really amazed them.

Michael Hauser


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