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Variables - Independent - Dependent.
The variable which is chosen for
an investigation
by the person doing the experiments is called the independent variable.
The thing being affected is called the dependent variable.
For example, the rate of the reaction
between hydrochloric acid
and
calcium carbonate can be measured by looking at
the rate of production of carbon dioxide
gas.
If we look at how the temperature of the hydrochloric acid
affects the rate of carbon dioxide production,
then temperature is the independent variable
and the rate of carbon
dioxide production is the
dependent variable.
If we look at how the concentration of the hydrochloric acid
affects the rate of carbon dioxide production,
then concentration is the independent variable
and the rate of carbon
dioxide production is the
dependent variable.
It is important to choose values
of the variables which are appropriate
for the experiment. The first experiment will be a trial run
which will tell you the quantities
which you need
(for example the amount of hydrochloric acid and calcium
carbonate)
and the appropriate conditions
(for example the temperature range or concentration
range).
A plot (graph) of the results will often
show a more interesting region
where a pattern is changing quickly. It will be necessary
to repeat the experiment with measurements closer together to
show
more detail in a region where a pattern is changing
quickly.
The independent variable is plotted on the X axis of a graph.
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