Constant or Controlled Variables 8 th Grade Science
Mar 27, 2015
Constant or Controlled Variables
8th Grade Science
What is a Constant Variable?
• A constant variable is also called a Controlled variable. (or Extraneous variable)
• It is the parts of the experiment that have to be kept the same so the experiment is a fair test of the IV.
List the MOST important ones.
• There can be several variables that need to be controlled or kept the same in the experiment.
• To save time and space, just focus on the 3 variables that would have THE MOST INFLUENCE on the outcome of the experiment.
Where do you find it?
• Listing constant variables requires you to use your prior knowledge about the subject.
Target Practice
• Think of the constant variables in #1 on your worksheet:
• Does how fast a rose bush grows depend on the amount of sunlight it receives?
MOST influential variable
• Eliminate the IV (sunlight)!!!
• Look for OTHER things BESIDES the Independent variable that would influence the outcome (DV) of the experiment.
• Use your PRIOR knowledge about what a plant needs to grow.
Think…What causes bacteria to thrive?
• #2 Do bacteria reproduce at a faster rate if the temperature is warmer?
Got Bacteria??List the Constant Variables:
•Amount of moisture
•Amount of light
•nutrients
Try #3 on Your own
• What are all of the variables you have listed?– Amount of food ─environment– Type of chicken ─nesting materials– Size of chicken– Age of chicken– Amount of water– Temperature
Try #3 on Your own
• What are the most important?– Amount of food– Type of chicken – Size of chicken --Temperature
--Age of chicken ─environment– Amount of water --nesting materials– Health of chicken