What happens to the pH in the presence of an acid?

When an acid is introduced to a solution, it releases hydrogen ions (H+) which increases the concentration of these ions in the solution. As the concentration of hydrogen ions rises, the pH of the solution decreases. The pH scale ranges from 0 to 14, with lower values indicating more acidic conditions. Therefore, the presence of an acid lowers the pH, making the solution more acidic. This understanding of acids and pH is a fundamental concept in biology and chemistry, as it affects various biological processes and reactions.