Tim makes a volcano demonstration for a class. He crafts the volcano out of clay, and then pours vinegar into the baking soda that is inside the volcano. What would be the best way for Tim to turn this demonstration into an experiment? He could pour the same amount of vinegar into several different volcanoes containing baking soda, repeating the demonstration. He would be answering the question “What happens when I pour vinegar into baking soda?” He could time how long the volcano bubbles after he pours the vinegar into the baking soda. He would be answering the question “How long will my volcano bubble?” He could measure how far the bubbles travel across the laboratory table after he pours the vinegar into the baking soda. He would be answering the question “How far will bubbles travel across a flat surface?” He could add different amounts of vinegar to the same amount of baking soda and time how long it bubbles each time. He would be answering the question “How does increasing the amount of vinegar affect the amount of bubbles that form?”

An experiment has to take into consideration the variability of the process because each time it is run you will get a slightly different result. The more repetitions you have, the closer you will get to a better understanding of the mechanism you are studying. So the best way for Tim to turn his demonstration into an experiment would be the first choice, by using three volcanos, or preferably more.