BTB (bromothymol blue) is an indicator that changes to yellow in the presence of carbon dioxide (CO 2 ). In neutral solution, BTB is green-blue.

A student was investigating photosynthesis and respiration. She filled four test tubes with water and BTB. She placed water plants in one test tube, water insects in another test tube, and both water insects and plants in another test tube. When she checked the color of the liquid in the test tubes after four hours, she observed the following.

Question

BTB (bromothymol blue) is an indicator that changes to yellow in the presence of carbon dioxide (CO  2  ). In neutral solution, BTB is green-blue.   



A student was investigating photosynthesis and respiration. She filled four test tubes with water and BTB. She placed water plants in one test tube, water insects in another test tube, and both water insects and plants in another test tube. When she checked the color of the liquid in the test tubes after four hours, she observed the following.

anonymous · Answer

What was  most likely  present in test tube 2?   

 


 
     A     water and BTB only    
     B     water, BTB, and insects    
     C     water, BTB, and plants    
     D     water, BTB, insects, and plants

anonymous · Answer

|dw:1394054856140:dw|

anonymous · Answer

help pls

abb0t · Answer

Where are you lost? This looks fairly straight forward.

anonymous · Answer

I don't know the answer for this question?... can u help me pls

abb0t · Answer

You wrote up there, "$changes~to~ yellow~ in ~the~ \color{red}{presence ~of~ carbon ~dioxide}$" <--- what does that indicate to you?

abb0t · Answer

Well, let's think about this, if you get a yellow color, that means CO$_2$ is present. Now, think about this, do plants make CO$_2$??

abb0t · Answer

Do insects make CO$_2$? How is it used?