Shakita wants to know if the pH of an open can of soda changes over time. To test this, she designs an experiment that will involve the following steps.
Open a can of soda and measure the pH.
Allow the open soda can to rest undisturbed on a level countertop at room temperature.
Measure the pH of the open soda can every day at the same time for ten consecutive days.
What is the dependent variable in Shakita's experiment?