Variables in Science
Objectives:
•
-
Students will be able to identify:
The independent variable
The dependent variable
The controlled variable or constants
in an experiment
What are
variables?
Variables are things
that vary and
change.
3 Types of Variables
• In an experiment there are 3 variables:
1. An independent variable
2. A dependent variable
3. Controlled variables that are sometimes
called constants
Let’s look at each type.
Independent Variable
• The independent variable is the part of the
experiment that you decide to change.
Think Independent = I change
For example:
• An experiment testing to see if temperature
of water effects the amount of sugar that will
dissolve
• Ask - what am I changing?
• You would change the temperature of the
water
• Water temperature is the independent
variable
Another example:
• An experiment testing the effect of different
amounts of fertilizer on plant height
• Ask - what am I changing?
• You would change the amount of fertilizer
• The amount of fertilizer is the independent
variable
Dependent Variable
• The dependent variable changes because of
the independent variable.
• The dependent variable is what is measured in
the experiment.
• Think Dependent Variable = Data
• What is the data you are collecting in the
experiment? What is being measured?
For example:
• An experiment testing to see if temperature
of water effects the amount of sugar that will
dissolve
• Ask – what is the data?
• You would collect data on the amount of sugar
that dissolves
• The amount of sugar is the dependent
variable
Another example:
• An experiment testing the effect of different
amounts of fertilizer on plant height
• Ask - what is the data?
• You would collect data about the height of the
plant
• The plant height is the dependent variable
Controlled Variables or Constants
• Controlled variables or constants are the parts
of the experiment that must stay the same.
• The controlled variables make the experiment
a fair test.
• Think of controlled variables as the
unchanging parts of the experiment.
• Think constant = No Change
change
For example:
• An experiment testing to see if temperature
of water effects the amount of sugar that will
dissolve
• Ask – what must stay the same to be fair?
• Same container, same amount of water, same
type of sugar
Another example:
• An experiment testing the effect of different
amounts of fertilizer on plant height
• Ask – what must stay the same to be fair?
• Same fertilizer brand, same type of plant,
same measurement standard, same amount
of water and light
Your turn:
• A test to determine which type of ball (golf,
basketball, ping pong, or tennis) bounces the
highest when dropped
What is the independent variable?
What is the dependent variable?
What are some of the controlled variables or
constants?
Discuss your answer with your shoulder partner.
Answers
• Independent variable = I change
The type of ball
• Dependent variable = data
The height of the bounce
• Controlled variable or constants = no change
for a fair test
All balls must be dropped from the same
height in the same way
Graphing
• When graphing the data, think DRY MIX – the Dependent variable goes on the Y
axis and the Independent variable goes on the
X axis
Dry dependent
Mix - independent
No monkey-ing around!
You are ready to identify variables.