Variables Notes

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

Independent variable The 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 Variable As many parts of the experiment that can be kept constant. The more kept constant the better your experiment.

Control Group This 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 Group This 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 Question Do diet cans and regular cans of coke float the same when placed in water?

Hypothesis If Independent variable, then dependent variable. Specific prediction EX: 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 Growth Question: 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 1 Independent Variable: Air type Dependent variable: mold growth Control: piece of bread in the cupboard with dry air

Experiment 2: Ice melting Question: 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 2 Independent variable: salt vs. no salt Dependent variable: rate of melting Control: container with no salt