The most important state in determining the state of a substance is
temperature. This is because the kinetic energy of a substance's
molecules depend on its temperature. For example, an increase in
temperature speeds up the movement of molecules. A decrease in
temperature slows down the movement of molecules.
This is
important because by increasing or decreasing a substance's temperature,
you are also adding or removing energy from it. And when a substantial
amount of energy has been added or removed, a substance can change its
state from solid > liquid > gas or the other way around.
