Student sheet
name_________________________
Title: Watching Photosynthesis
Introduction: Plants take in and give off gases as they use photosynthesis to make
food. What gas do they give off? What do they take in? In this activity, you will test
photosynthesis with an indicator chemical that turns yellow in CO2. It is called
Bromthymol Blue and is blue in a solution that does not contain CO2.
Materials: pond plant, 2 test tubes, light source, large beaker, 2 stoppers, straw,
Bromthymol Blue
Procedure:
1. Get a beaker with 50 ml of Bromthymol blue solution. Blow bubbles in it with the
straw until it changes to a green color. Pour this solution into 2 test tubes, filling them
to the top.
2. Put a stopper on one tube and add a piece of pond plant to the other. Put a stopper
on it also. Which is the control?
3. Set test tubes in the beaker. Find a place next to the light source to set it. Describe
here where you put yours:________________________________
Wait 25 minutes.
5. Remove the tubes from the light. Take the pond plant out of the test tube and
compare the water in the tube to the control. Draw your results and show the colors.
6. Share your results with the class. Do not throw away the Bromthymol blue solutions
Prediction: Which light source will allow the most photosynthesis?
Data:
With pond plant
Without plant
Analysis:
1. What gas in your breath made the Bromothymol Blue turn green?
2. Why does your body produce this gas?
3. Which light source helped the plant turn the color back to blue best?
4. Why?
5. Why does the plant turn the Bromothymol blue back to blue?
6. What is the formula for photosynthesis?
7. Which part of it did you test today?
Conclusion: