What's the experiment?
Dry ice is solid carbon dioxde. Sometimes people put dry ice into a pan of water and are amazed at the thick clouds that are produced, but that is an experiment, that's just a gimmick, a demonstration, if you will.
The dry ice in water quickly undergoes sublimation at -77C and then cools the air above the water and the water vapor in the air condenses to water droplets which make up the cloud.
Chemistry experiments rarely involve a "control." Teacher who talk about "controls" are seldom trained in chemistry and frequently come from a biology background, or very little since background at all. They just assume, because they read about "controls" in their general science book that it should apply to chemistry as well. A fundamental principle in science is to manipulate one variable at a time. The closest thing to a "control" is to keep other variables constant.