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Use the Tools

Do you recognize the laboratory tool above? It’s a type of sterile Petri dish called an agar plate, and it’s
used to culture bacteria (or fungi). Here’s another quick review of some basic lab equipment.

• Microscope
• Graduated cylinder
• Balances
• Bunsen burner
• Calorimeter
• Colorimeter

Knowing your way around the metric system is another skill you should have. You should remember the
basics: the base units employed by the metric system include meter (length), gram (weight), and liter
(capacity). Each of these base-unit terms uses similar prefixes, such as kilo- (one thousand times the
base unit) and milli- (one-thousandth of the base unit).

Scientific Experiments

Conducting scientific experiments is an important part of formulating and testing hypotheses in the
scientific method. The experiment will test predictions made by the hypothesis or model, so a scientist
must be able to plan and conduct valid experiments.

In the ideal case, an experiment will change only one variable at a time. There will also be a control
experiment . For example, there is a myth that it is possible to balance an egg on its end on and only on
the equinox. A television news show might perpetuate this myth by showing an egg balanced on end
during the equinox. However, such an experiment is not properly designed and therefore proves
absolutely nothing.

To properly test the hypothesis that there is something special about the equinox that allows an egg to
balance on end only on that day, we need a control experiment. The experiment should be repeated on a
day that is not the equinox. If the egg balances on that day, then there is nothing special about the
equinox, and the experiment proves the hypothesis wrong. It is also important that only one variable be
changed at a time. If, for example, you perform this experiment on a sidewalk on the equinox and on the
countertop the other day, you are changing two variables. You might reach the incorrect conclusion that
there is something special about the equinox when in fact the result stems from the different surfaces.

Complex Sets of Data

In areas of science, such as medical research, where the systems being studied are too complex to
change only one variable at a time, the experiment must be repeated on a large number of subjects. A