What are substances in solutions that change color at a specific pH called?

Substances in solutions that change color at a specific pH are known as indicators. They are typically weak acids or bases that exhibit different colors depending on the hydrogen ion concentration in the solution, which corresponds to its pH level. This property makes them essential in various chemical analyses and titrations, as they provide a visual cue for the pH of the solution.

Indicators work by undergoing a chemical change when the pH reaches a certain threshold, causing a shift in color. This change can be observed visually, allowing for easy monitoring of pH levels in various applications, including environmental monitoring, food safety tests, and laboratory experiments.

While solvents are the substances that dissolve other materials, and buffers are solutions that resist changes in pH upon the addition of an acid or a base, neither of these would change color in response to pH. Catalysts, on the other hand, are substances that accelerate a chemical reaction without being consumed in the process and do not pertain to changes in color related to pH. Therefore, indicators are distinctly characterized by their ability to change color based on specific pH levels.