Science Buddies: "Ask an Expert"

What are the variables in this project?
I am always confused with the constant and the variables, the control, independent, dependent...
thank you

The independent variable is the ONE thing you change. The dependent variable is what happens as a result of changing the one thing. The constants are everything else - you want to keep as much as possible *exactly* the same so you don't mess up your results.

So let's say I wanted to know the effects of putting air in a balloon. I'll measure the size of the balloon without air then attach it to a pump. If I pump it once and measure, then again and measure... I'll see that as I put more and more pumps in, the balloon get bigger around. I also want to repeat this several times to make sure I have good data, so I'll use balloons of the same kind and color (preferably from the same bag).

In this experiment, the number of air pumps is the independent variable. Since the size (diameter) of the balloon gets bigger with each pump, the size is the dependent variable. I'm using the same pump, pumping exactly the same way, using balloons from the same bag - all of these are constants.

Take a look at https://www.sciencebuddies.org/science- ... bles.shtml and think about your experiment. What do you think the variables are?

It's also useful to know that the independent variable is sometimes called the manipulated variable, which, as HowardE stated, is the only thing you change in an experiment.

The dependent variable is also called the responding variable. An easy way to figure out the dependent variable is to look at what results you're recording from your experiment. The thing that you're measuring (in this case balloon size) is the dependent variable.

Hi eyelinacha,
I saw that you mentioned the "constant" and the "controlled variables" as if they were different from one another. Just to clarify, the constants and the controlled variables are one and the same.
Controlled Variables:
So, the controlled variables in the experiment HowardE explained would be the constants he referred to e.g. "the same pump, pumping exactly the same way, using balloons from the same bag". We usually keep certain things constant when doing an experiment to make sure that the manipulated variable(s) is/are the only thing(s) effecting the dependent variable(s). Balloons from different bags may vary in volume, type of material etc..which might affect the dependent variable of this experiment, giving us false data because we just want to see the effect of filling a balloon with air, not the effect of anything else on the balloon. It's very important to have controlled variables because without them your data may be faulty and your experiment inconclusive.
Control Groups:
You also mentioned having controls in an experiment. Controls or control groups are similar to controlled variables because they are used to make sure an experiment is conclusive, and is actually doing what it seems like it's doing. They also stay the same throughout that experiment. Control groups are basically another setup for your experiment without the manipulated variable. We compare control groups to our actual experiments to observe the difference between what normally happens and what happens when you effect your experimental setup with your manipulated variable. For example, if I were testing the effects of submerging gummy bears in water on the size of the gummy bears, I would have a control group of dry (outside of water) gummy bears so that when I have to collect the data for my experiment, I can compare the gummy bears from the water to the gummy bears I left outside of the water-now I can tell if there was a difference between the two.
I hope this helped and good luck!