Dear members of the Teacher Connection,
I, along with my co-educator Todd McMenamy, would like to present to a clear and simple solution to the difficulties surrounding the teaching of chemical solubility guidelines to general and honors chemistry classes. This innovative technique clarifies the solubility guidelines and precipitates understanding among students who often become frustrated by the multitude of solubility rules and exceptions that often seem contradictory and confusing. We have designed the SOLUBILITY PYRAMID as an innovative teaching technique that removes most of the angst from learning the various rules and guidelines associated with the solubility guidelines.
The solubility pyramid basically consists of a top down tiered approach to discerning if a compound is soluble (aqueous) or insoluble (solid precipitate). The solubility pyramid can be posted in the chemistry lab, in the class room or copied onto a periodic table and is often memorized easily by most students in minutes.
The pyramid is broken down into three tiers to discern
if a compound is soluble:
Step
1 Refer to the pyramid’s top or first tier. If the
compound contains NO3 - or NH4+
then the compound is soluble and there are no exceptions.
Step 2 If the compound does not contain items in the
first tier move to the second tier. If the compound contains
either Group 7 or SO4-2 then the compound
is soluble and there are 4 exceptions Ag, Hg, Ba and Pb.
Step 3 If the compound does not contain items in the
first two tiers move to tier three. If the compound contains
CO3-2, OH- or PO4-3
then the compound is an insoluble solid precipitate.
As veteran teachers of chemistry we have found the solubility pyramid to be an excellent tool that can be used to determine if a compound is soluble.
Please consider both Dr. Howard Wright and Mr. Todd McMenamy for the Hach Scientific Foundation Outreach Program grant for presenting this innovative approach to teaching solubility to general and honors chemistry students.
Dr. Howard Wright
Mr. Todd McMenamy
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