19. CER. A group of students were interested in showing photosynthesis occurring visually. They decided to use bromothymol blue which is an
indicator that turns green when there is a high concentration of carbon
dioxide and blue when there is a low concentration of carbon dioxide in
water. All the tubes started out blue, but students blew carbon dioxide
into two of the test tubes turning them green. They left one test tube of
each color as their control and put a piece of aquatic plant in the other
two tubes. Then, they put all four of these tubes outside (Monday 7 am).
When the students checked their tubes in the afternoon (Monday 1 pm),
they were so excited to see that tube D had turned blue! Carbon dioxide
was going away and being replaced with oxygen. When the students
checked their experiment early the next morning, tube B and D had both
turned green! Did photosynthesis occur during the experiment? Support
your claim with evidence explain your reasoning. *