Identifying Variables in Science

Types of Variables Scientists use controlled experiments to figure out how the natural world works. A controlled experiment is a test where a scientist only changes one variable at a time.Independent Variable: ischanged on purpose by the scientist.Dependent Variable:changes in response to the independent variable.Control or Constant:factor the scientist wants to stay the same throughout the experiment.Directions: Read the following questions and identify the variables. "How does the size of a dog affect how much food it eats?"What is the dependent variable? The size of the dog Amount of food Brand of food "Does the temperature of a classroom affect student performance?"What is the independentvariable? Subject Student performance Temperature “Does running in the morning increase my heart rate more than running in the evening?”What is the dependent variable? Heart rate Running Time of day "How does a person's age affect their reaction time?"What is the independent variable? Age Reaction Time Time of year "Does worker happiness increase the amount of work they can do?"What is the dependent variable? The worker Worker happiness Amount of work done "The height of bean plants depends on the amount of water they receive."What is the independentvariable? height of plant type of bean plant amount of water "An investigation found that more bushels of potatoes were produced when the soil was fertilized more."What is the dependentvariable? type of potatoes amount of fertilizer number of bushels of potatoes "The higher the temperature of the air in the oven, the faster a cake will bake."What is the independent variable? cake bake speed size of cake temperature of oven "A student tested how adding paper clips to a paper airplane affected the distance it would fly."What is thedependent variable? number of paper clips shape of paper airplane distance flown "The amount of sunlight affects the size of the plant."What is the independent variable? amount of water amount of sunlight size of plant Can you tell the differences between variables? Match the type of variable with its definition. Independent variable the variable changed by the scientist Dependent variable the variable that responds Constant factor that stays the same Sort the variables into 2 groups: a group that stays the same and a group that does not stay the same. Stays the Same Constant Control group Changes Independent variable Dependent variable