Explain what happens to the pH of an acid as the acid is diluted with water.

The pH scale is a measure of the concentration of hydrogen ions (H⁺) in a solution. A lower pH indicates a higher concentration of H⁺ ions (more acidic), while a higher pH indicates a lower concentration of H⁺ ions (less acidic). When an acid is diluted by adding water, the total number of H⁺ ions remains the same, but the total volume of the solution increases. This causes the concentration of H⁺ ions (moles per unit volume) to decrease. Because the concentration of H⁺ ions has decreased, the solution becomes less acidic, and its pH value increases, moving closer to the neutral pH of 7.