How can you explain even though you continue to add pure water into a substance, even though the resultant pH might differ a little, the acidity or alkalinity of the substance still remains the same to that of substance?

According to the kinetic-molecular theory, what happens to a liquid when it is transferred from one container to another? the volume and the shape stay the same. the volume increases to fill the new container, but the shape stays the same. the volume stays the same, but the shape changes to fit the new container. the volume and the shape change to fill the new container.