Variables Notes

VariablesVariables are parts of an experiment that can be changed or controlled.

Independent variableThe variable that is manipulated, chosen to

be observed, or purposefully changed.

Dependent Variable The variable that is measured. This is the

resulting data due to the influence of the independent variable.

Control VariableAs many parts of the experiment that can be

kept constant. The more kept constant the better your experiment.

Control GroupThis is a group of subjects or items that is not

exposed to the independent variable. We know what will happen to this group and helps us understand if our experiment worked.

Experimental GroupThis group is exposed to the independent

variable. We don’t know what will happen to these items or subjects. The things we are testing.

Testable QuestionDo diet cans and regular cans of coke float

the same when placed in water?

HypothesisIf Independent variable, then dependent

variable.Specific predictionEX: If a can of diet coke and a can of regular

coke are placed in a tank of water, then the diet can of coke will float and the regular can of coke will sink because diet soda has less sugar making it less dense.

Experiment 1: Mold GrowthQuestion: Does humidity affect mold growth?Observations: Mary noticed that bread in her

cupboard seemed to get moldy really fast in July when it was really hot and humid. In September, when the air was dry and cooler, her bread stayed fresh longer. She wants to know if there is a relationship between humidity and mold growth.

Hypothesis: If I put a slice of bread in a container with water vapor and high humidity, and a piece of bread in a container that has dry air, then the piece of bread in the humid container will grow mold faster than the bread in the dry container because bread gets moldy faster with humidity.

Experiment 1Independent Variable: Air type

Dependent variable: mold growth

Control: piece of bread in the cupboard with dry air

Experiment 2: Ice meltingQuestion: Does ice melt faster by adding salt?Observations: After a snow and ice storm

Henry noticed big trucks dumping salt on the roads. When he asked why, his mother said, “The ice melts faster when they put salt on it.” He wanted to test this idea.

Hypothesis: If I have two containers of ice and add salt to one, then I will find that all of the ice in the container with salt will melt faster because salt speeds up the rate of ice melting.

Experiment 2Independent variable: salt vs. no salt

Dependent variable: rate of melting

Control: container with no salt