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Using
an Overhead Projector to Conduct Lab Experiments
The
overhead projector is a great tool for conducting class experiments.
It can work very well for younger students, quick demos to highlight
a lecture point, or when the chemicals involved are too expensive
or reactive to use in classroom quantities.
For
example, crystals that are much too small to be visible past the
first row of students can easily produce large and impressive
images. Another
useful application for the overhead projector is viewing chemical
reactions. This is easily accomplished because beakers have a
transparent bottom and when placed side-by-side on the overhead,
gives the illusion that every student in the classroom is standing
over the beakers with a perfect view of the results. A great classroom
exercise using this approach compares the reactivity of metals
with dilute hydrochloric acid. Let's say you want your students
to test the reactivity of calcium, magnesium and aluminum with
this acid. Place a few milliliters of the dilute HCl in each of
three 100 ml beakers and align them in a row on the projector
platform. Place a blank transparency sheet beneath the beakers
so you can label each container. Drop a small piece of Ca metal
into the first beaker. Discuss the results of the reaction with
your students and have them record their observations. Repeat
this process with a small piece of Mg and then Al. Ask students
to provide a balanced chemical equation for each reaction. The
Quantum Chemical Reactions Tutor and Balancing Chemical Equations
Tutor will be very useful here. These Tutors can complete and
balance the chemical equations as well as answer any question
students may have about each reaction. View a demo at www.quantumsimulations.com/demo.html.
The
results from this investigation will enable your students to easily
list the metals in order of reactivity. On a broader scale, the
results provide significant insight into the trends on the periodic
chart. This classroom experiment can be done quickly, easily,
and with little cleanup.
CAUTION:
You may wish to place a blank transparency under the crystals
or beakers to protect the overhead projector and facilitate easy
clean-up. Take all recommended precautions when handling strong
acids and active metals. Refer to your lab manuals and MSDS sheets
regarding the proper handling of chemicals.
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