Answer:
The pH of a solution is a measure of the molar concentration of hydrogen ions in the solution and as such is a measure of the acidity or basicity of the solution.
Lol now way he answers this
A method of procedure that has characterized natural sciences the 17th century, consisting in systematic observation, measurement, and experiments, and the formulation, testing, and modification of hypotheses.
I believe it is phase change because of how that can also happen in a physical change.
