Answer:
Independent variable is the one which can be changed, and manipulated in an experimental process. Dependent variable is the one which cannot be changed or manipulated, but the effect of changes that occurs in an independent variable is observed on a dependent variable. A dependent variable is an outcome of an experimental procedure. For example, the effect of amount of water on the height of a plant, here the amount of water is the independent variable whereas, the height of plant is the dependent variable. A control variable is a variable, which is used as a standard for an experiment. It remains as constant entity.
In the given situation, the temperature is an independent variable as the level of temperture can be easily manipulated to observe the effect on a boiling substance, which is a dependent variable. A control varaible can be a standard boiling substance, on which no effect of temperature occurs.