What changes that occur when a chemical solution goes from pH 5 to pH 8?

The pH is a scale used to measure the acidity or basicity of a solution in which water is the solvent. The scale goes from 0 (most acidic) to 14 (most basic), with 7 being neutral. If the pH goes from 5 to 8, then you can see from the scale that substance goes from acidic to basic.

As reference, one of the most acidic substances is battery acid while one of the most basic is drain cleaner. An example of a neutral substance is blood, which has a pH of 7.4.