What does the change of bromothymol blue from blue to yellow signify during the experiment?

The change of bromothymol blue from blue to yellow indeed signifies an increase in carbon dioxide levels. Bromothymol blue is a pH indicator that responds to changes in acidity. In a solution, if carbon dioxide levels increase, it leads to the formation of carbonic acid, which releases hydrogen ions (H+) and lowers the pH of the solution. As the pH decreases, the color of bromothymol blue shifts from blue (which indicates a more alkaline or neutral pH) to yellow (indicating an acidic environment). This color change is a visual representation of the chemical reaction occurring due to an increase in carbon dioxide, highlighting the relationship between CO2, acidity, and pH.

This knowledge aligns with processes such as respiration, where organisms exhale carbon dioxide, which in turn reflects the CO2 levels in the environment being tested. Understanding this connection is fundamental in many biological contexts, especially in respiration and photosynthesis studies, where carbon dioxide levels directly impact pH and overall cellular processes.