Chapter 2 - Variables and Experiments
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Variables are an important part of science projects and experiments.

What is a variable?
Basically, a variable is any factor that can be controlled, changed, or
measured in an experiment. Scientific experiments have several types
of variables. The independent and dependent variables are the ones
usually plotted on a chart or graph.

Types of Variables

Independent Variable
The independent variable is the one condition that you change in an
experiment.

Example: In an experiment measuring the effect of temperature on
solubility, the independent variable is temperature.


Dependent Variable
The dependent variable is the variable that you measure or observe.
The dependent variable gets its name because it is the factor that is
dependent on the state of the independent variable.

Example: In the experiment measuring the effect of temperature on
solubility, solubility would be the dependent variable.

Manipulated Variable
A manipulated variable is a variable that you have said in your
hypothesis makes the difference in the outcome of the experiment.


Controlled Variable
A controlled variable or constant variable is a variable that does not
change during an experiment.

Example: In the experiment measuring the effect of temperature on
solubility, controlled variable could include the source of water used in
the experiment, the size and type of containers used to mix chemicals,
and the amount of mixing time allowed for each solution.\


Extraneous Variables
Extraneous variables are "extra" variables that may influence the
outcome of an experiment, but aren't taken into account during
measurement. Ideally, these variables won't impact the final conclusion
drawn by the experiment, but they may introduce error into scientific
results. If you are aware of any extraneous variables, you should enter
them in your lab notebook. Examples of extraneous variables include
accidents, factors you either can't control or can't measure, or factors
you consider unimportant. Every experiment has extraneous variables.

Example: You are conducting an experiment to see which paper
airplane design flies longest. You may consider the color of the paper
to be an extraneous variable. You note in your lab book that different
colors of papers were used. Ideally, this variable does not affect your
outcome.
Variables