For an experiment to give answers you can trust, it must have a control. A control is an additional experimental trial. It is a separate experiment, done exactly like the others. The only difference is that no experimental variables are changed. A control is a neutral reference point for comparison.
Dependable controls can be the hardest part of a project.
Materials and Equipment Make a list of the things you will need to do the experiment. If you need special equipment, a local high school, college or business may be able to loan it to you. Do the Experiments and Record the Data Experiments are often done in series. A series of experiments can be done by changing one variable a different amount each time. A series of experiments is made up of separate experimental trials.