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THE INTRODUCTION
The introduction should primarily
give a statement of the purpose of the experiment. You
might also say why the experiment is important (5: 55-56). In addition
you might want to explain some of the important concepts relevant to your
experiment. In chemistry you should include the chemical equations for
the chemical reactions involved in the experiment. The
description of the experiment in your lab manual is often a good place
to start in writing your own introductions. Here are some sample statements
of purpose based on experiments in "Basic Laboratory Principles in
General Chemistry with Quantitative Techniques," by Bramwell, Dillard,
and Wieder:
The purpose of this experiment is to study the relationships
between electrical current and chemical reactions using Faraday's
law.
The purpose of this experiment is to give a rough estimate of
Avogadro's number using measurements of the volume and area of a molecular
monolayer in a fatty acid.
The purpose of this experiment is to construct a gavalnic cell
and measure its reduction potential.
However, you might want to explain some of
the important concepts related to the experiment. For example, you might
elaborate each of the above examples as follows:
The purpose of this experiment is to study the relationships
between electrical current and chemical reactions using Faraday's
law. According to Faraday's law, one equivalent of an ion is produced
at each electrode for each 96,487 coulombs of charge passed through
the cell.
The purpose of this experiment is to give a rough estimate of
Avogadro's number using measurements of the volume and area of a molecular
monolayer of a fatty acid. Because the thickness of the film formed
by a fatty acid on the surface of water is usually one molecule thick,
we can calculate roughly the volume of one molecule of the fatty acid
and use this to calculate the number of molecules per mole, which
is Avogadro's number--6.022 X 1023.
The purpose of this experiment is to construct a gavalnic cell
and measure its reduction potential. The reduction potential is a
measure of the tendency of a particular redox couple to gain or lose
electrons.
Each of these examples can, and perhaps should,
be further elaborated to explain the concepts involved. Next is a brief
introduction that might be suitable for our Volta's cell experiment.
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