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Unit 4.7 Using Concrete Examples
Several demonstrations of basic chemical concepts are presented,
from computer animations to nuts-and-bolts type presentations.
Both help students visualize new concepts.
Video program cues: 41:25 — 57:26
Water dissociation
"Let me show you an example of an acid-base
reaction, which occurs just in liquid water…we start
off with two water molecules which just hit one another.
They aren't bonded together but they have a fight, and a
hydrogen atom is involved in a tug of war between the two
oxygens. What is actually moved from one molecule to the
other is the hydrogen atom, not the electrons. It's like
a flea jumping from one dog to the other. You don't see
the flea, but you can see the itching...."
Dr. Roy Tasker
Associate Professor, Univ. of Western Sydney
Electrolytes in solution demonstrations
Irene Walsh teaches about conductivity of strong and weak.
Electrolytes in solution, as well as about the dissociation
of water.
Activity
Reading
Morikawa, T.; Williamson, B. E. (2001)' Model for Teaching
about Electrical Neutrality in Electrolyte Solutions, 'Journal
of Chemical Education, Vol. 78, No. 7, pp: 934-936.
What are real chemicals?
Teachers’ forum
"We have to break this notion
that you are not really doing chemistry unless you are using
'real' chemicals. I mean, what is a real chemical and what
is not?"
Caryn Galatis
Thomas A. Edison High School, Virginia
"We have to start letting everybody know that everything
is a real chemical. Vinegar is a real chemical, lime juice
is a real chemical."
Dr. Michael Clarke
Duke Ellington School for the Arts, Washington, D.C.
"And that anything can be dangerous if it is used in
an incorrect way."
Sharon Walton
Watkins Mill High School, Maryland
"The kids have this misconception, too. If it is around
the house then it is not chemicals."
Caryn Galatis
Thomas A. Edison High School, Virginia
"That’s one that I love to address by giving them
pH strips to take home. Let them find out that the chemicals
that they have at home have a higher concentration than
anything that we are allowed to give them in the lab by
the safety rules. I think that the idea that everything
else is not chemicals, causes them to have this divorced
world of chemical systems, which is not part of real everyday
life."
Tom Pratuch
Annandale High School, Virginia
"Here is a challenge that we have, though: If we are
going to talk about household chemicals as a basis for their
understanding of chemistry, we should also have to teach
students how to apply some of the techniques and tools that
chemists use in the lab to working with these materials.
What we are trying to do is to use these everyday substances,
and give the kids the opportunity to use the tools that
traditionally chemists use."
Dr. Leslie Pierce
Thomas A. Edison High School, Virginia
"It can be a simple lab as the one that we do in the
observation on pH, once we learn what acids and bases can
do. They can try out a lot of acid-base indicators; they
can then extend it to thin layer chromatography, which is
a very common technique, and spectroscopy. Vegetables and
fruits and their colorful components can be used for a lot
of different things."
Caryn Galatis
Thomas A. Edison High School, Virginia
"To get them to accept whatever your data is, and the
conclusion that you then reach, based on the analysis of
whatever you actually measured, and then explain the discrepancy
if in fact it is obviously discrepant from what it should
be. Focusing on such thought skills and affecting their
way of thinking is more than just chemistry."
Tom Pratuch
Annandale High School, Virginia
Links
- From the EPA,
a tour of chemicals in and around the home. Also, click
on the items on the left side of page for more information.
- An extensive list of cited references for teaching
to student
misconceptions in science.
Reading
Sanger, M. J.; Greenbowe, T. J. (1997)' Students' Misconceptions
in Electrochemistry Regarding Current Flow in Electrolyte
Solutions and the Salt Bridge, 'Journal of Chemical Education,
Vol. 74, No. 7, pp: 819-823.
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