What is a control and variable in an experiment?

i am doing and experiment with sodas, glass and nails. which is the variable?|||A control is an experiment that you go off of. Like if you are testing different plant fertilizers, the control would be an unfertilized plant. In your case, the control would be just a nail in a glass, which we all know wouldn't deteriorate and so you don't really need a control. It wouldn't hurt to through it in there though.





The variable would be your different sodas. As long as the nails and glasses all stayed the same, they wouldn't affect the experiment.





So say you have Diet Coke, Coke, Pepsi, Mountain Dew, and other sodas. If you poured the exact same amount into different glasses, all with the same shape and same size of nail, the soda would be the only thing changing from experiment to experiment. Thus they would be the variables.|||Whichever you want to be the variable.





Typically, you try to find a relationship between two measurable quantities.





The one you adjust is called the control, or "independant variable"


This typically affects the other quantity, which is known as the "dependant variable".





Assuming by "soda" you mean carbonated beverage (pop or soft drink); and by "glass" you mean a "tumbler" or other stemware; and by "nail" you mean a metal fastener, then you could do the following experiments:





1) find the ratio of volume of liquid to height of liquid with respect to the diameter of the glass. Diameter is one control. Either volume or height could be another control, and whichever you choose as the control, means the other is the dependant variable.





2) find how long it takes a nail to dissolve in a glass of pop. Controls: mass or length of nail, pH of pop, temperature of pop, volume of pop, nail material (iron, copper, etc). Dependant variables: time to dissolve.





3) determine the "packing fraction" of a glass full of nails. Calculate the volume of the glass from it's measurements. Fill it with nails. Add pop, until full. Empty pop, carefully measuring it's volume. Subtract from volume of glass to get volume of nails. Divide volume of nails by volume of glass to get packing fraction. Choose a different type of nail, and repeat. Nail type = control, or independant variable. Packing fraction = dependant variable.