Bromothymol blue is placed into water and a student blows bubbles into it to change the color to yellow. A plant is placed in each test tube. One is placed in the light and one is placed in the dark.

What will happen to the colors of the two test tubes and why it will occur?

The color of the bromothymol blue solution in the tube that was placed in a dark place for 24 hours turned from Green to Yellow. The test tube that was in the light area for 24 hours remained blue. In the test tube that was placed in the dark, respiration occurred and produced carbon dioxide. The carbon dioxide formed a weak acid and when mixed with the water it formed a weak acid thus the color of bromothymol changed to Yellow.

In the test tube that was placed in the dark, respiration occurred and produced carbon dioxide.