Science Buddies: "Ask an Expert"

I am doing a simple version of the Blood Spatter project measuring the diameter of the drops correlated with which height they are dropped from. Problem is, I think I am supposed to have a Control Variable in my experiment and I cannot figure out what it would be here? Help.

There are many controlled variables that you can mention here. A controlled variable is simply a variable that you try to keep the same throughout your experimental trials. The purpose of this is to make sure that only the manipulated variable is responsible for the differences in your results.

For your experiment, examples of controlled variables are: the type of liquid you use to simulate the blood, the surface that you are dropping the liquid on, and the amount of liquid in a drop. I'm sure you can think of many more.

Best of luck with your project!

-Karen

We are taught that the things like that (the surface, the fake blood, the dropper, etc.) are the "Constants". The Control Variable would be something you compare the Dependent Variable to - to show how much the dependent variable changes from the control during the experiment. I'm just stumped unless I drop water and measure that too?

Hi artsychikk,

It sounds like what you are describing is a "control group". For example, if you were measuring how adding fertilizer changes how tall a plant grows, then you would grow a set of plants without fertilizer as a control group. In your project, however, you do not have a control group in the same way that this plant project would.

In your project, you are measuring how height (your independent variable) affects the diameter of the drops (dependent variable). Your controlled variables (which your teacher called constants) are things such as the ones Karen described. If you are still confused, I would suggest talking to your teacher so that you can make sure you are defining your variables in the way that she or he wants you to.