How can the pH of a solution be altered?

The pH of a solution is a measure of its acidity or alkalinity, determined by the concentration of hydrogen ions (H⁺) present. One of the most direct and effective methods to alter the pH is by adding acids or bases to the solution.

When an acid, which donates H⁺ ions, is added to a solution, it increases the concentration of these ions, leading to a decrease in pH and making the solution more acidic. Conversely, adding a base, which accepts H⁺ ions or donates hydroxide ions (OH⁻), reduces the concentration of H⁺ ions in the solution, thereby increasing the pH and making the solution more alkaline. This ability to manipulate pH through the addition of acids or bases is foundational in many chemical processes, biological systems, and laboratory experiments.

Changing the physical state of a solution, adding or removing water, or heating might influence solubility or the concentration of solutes, but they do not have the same direct impact on pH as the addition of acids or bases does.