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www.njctl.org 5th Grade PSI Energy in Organisms
Photosynthesis & Cellular Respiration Lab
5th Grade PSI
Teacher’s Notes:
Teacher Background:
Cellular respiration occurs in both animals and plants. It’s a common misconception that
only animals have cellular respiration but both plants and animals use this process to
convert sugar into energy for cells. This means that both plants and animals need and
use oxygen (see reaction below). Photosynthesis and cellular respiration are in a
continual cycle. In this lab, we use our breath to model the waste product (CO2) from
cellular respiration in animals, while this occurs naturally amongst animals and plants.
Time:
This lab is designed to be split into two parts. Part 1 will take approximately 30 minutes
and Part 2 will take approximately 35 minutes. Plan to allow at least one hour in
between Part I and Part 2.
Materials:
Whole Class
Dropper
Bromothymol Blue (BTB)
Indicator
Photosynthesis-Cellular Respiration Cycle illustration from notes
Individual
Cellular Respiration Recording Sheet
Science notebook
Procedure:
Part 1
1. Students will be conducting experiments to discover if there is a relationship
between photosynthesis and cellular respiration.
2. Make sure they have all the necessary materials and supplies prior to beginning
the experiments. Instruct them to follow along with your demonstrations of steps
3. Model each step below and have students complete each step before moving on
to the next. Explain that students will complete the Cellular Respiration
Recording Sheets during each step of investigation.
www.njctl.org 5th Grade PSI Energy in Organisms
4. Explain that students will be working with an indicator. Ask if anyone knows what
an indicator is. If not, explain that an indicator is a substance that tells if another
substance is present or what that substance is. The indicator used, BTB, turns
yellow in the presence of carbon dioxide (CO2) and green-blue in the presence of
oxygen (O2).
5. Show students the beaker. Ask them to predict what will happen if they blow into
the beaker. Ask them to record their prediction on their Cellular Respiration
Recording Sheet. Ask several students to share their ideas and explain their
reasoning. (Students may say they are blowing carbon dioxide in and it should
turn yellow.)
6. Model how to put the plastic straw into solution and blow into it. Have students
blow into their beaker until they see a change in color (this may take a couple
minutes). Remind student to be careful not to drink the solution.
7. Instruct students to record their observation on the recording sheet.
8. Model how to set up the experiment:
Put elodea into one of the test tubes and use the funnel to fill the tube with
the BTB solution from the beaker.
Model how to fill the other test tube with only the BTB solution.
Model how to seal the test tubes with caps and carefully turn them upside
down and place them in the empty beaker.
9. Guide students in designing an experiment to observe cellular respiration.
Instruct students to draw and label their set up on their recording sheet along
with their hypothesis on their recording sheet.
10. Ask several groups to share their hypotheses. Discuss their ideas. Instruct
groups to put the beaker containing the two test tubes in the sunlight for at least
an hour or until the next day.
Part 2
1. After at least one hour in the sunlight instruct students to observe the test tubes
and record their observations on the recording sheet. Ask several groups to
share what they observed in both test tubes.
2. Ask the table groups to use what they know about photosynthesis to discuss
how/why the color changed (or not). Have students write their own answers on
their handouts.
a. BTB is an indicator. It changes color when carbon dioxide is present. It will
turn yellow when carbon dioxide is present and green when carbon
dioxide is in the process of being removed.
b. Expected Responses
www.njctl.org 5th Grade PSI Energy in Organisms
Cause Indicator change Explanation
Carbon Dioxide Solution turns yellow Exhale carbon dioxide by blowing into straw
Elodea + Solution + Sunlight
Solution turns from yellow -> green -> blue
Photosynthesis takes place converting the CO2
to O2
Solution + Sunlight Stays yellow This test tube has no
plant, CO2 is not converted.
c. Teacher Note: Through questioning make sure students understand that
photosynthesis took place when the elodea was put into the sunlight,
which allowed the elodea to remove the carbon dioxide from the solution
therefore turning it back to blue.
3. Ask table groups to discuss what they think would happen to the water with the
Elodea if a snail was added into the test tube. If needed, prompt students with
the idea that the snail is an animal—what would it contribute that the plant might
need?
a. Teacher Note: the snail would breathe into the water, causing the water to
turn yellow; but the plant would be photosynthesizing, releasing oxygen,
so the water would actually stay a bluish color
4. Ask students to recall the equation for photosynthesis, first in words, then using
the chemical formulas.
5. Write the word cellular respiration and photosynthesis equations on the board.
6. Ask students which side of the equation would represent the snail? Which would
represent the plant? Through questions, help students to see that cellular
respiration is the opposite reaction to photosynthesis.
7. Facilitate a discussion about the results of the experiment prior to instructing
student to complete questions 7 through 11 on the recording sheet.
www.njctl.org 5th Grade PSI Energy in Organisms
Photosynthesis & Cellular Respiration Lab Name:__________________________
5th Grade PSI
Experimental Question:
What is photosynthesis? What is cellular respiration?
How do plants gather and convert energy into food?
Purpose:
What is the process that plant go through to create energy? How do we consume and
process that energy? Plants use photosynthesis to make food and release oxygen and
plants and animals use cellular respiration to break down food (sugars) and release
carbon dioxide. Photosynthesis and cellular respiration are reverse processes. During
this lab you will investigate the processes of photosynthesis and cellular respiration.
Materials:
Per group or table groups
Safety goggles
2 - 250mL beakers (or clear cups)
Water
Plastic straw
Elodea or similar plant
2 Test tubes with caps
Funnel
Tray
Access Prior Knowledge
Complete the Photosynthesis/Cellular Respiration T chart with everything you know
about each item. Share out your thoughts with the class.
Photosynthesis Cellular Respiration
www.njctl.org 5th Grade PSI Energy in Organisms
Procedure:
Part 1
1. You will be conducting experiments to discover if there is a relationship between
photosynthesis and cellular respiration.
2. Make sure you have all the necessary materials and supplies prior to beginning
the experiments. Follow along with your teachers demonstrations of steps. Do
not move on until instructed to do so.
3. Wear on safety goggles for each step of the experiment. In this experiment you
will be using an indicator called BTB. This indicator turns yellow in the presence
of carbon dioxide (CO2) and green-blue in the presence of oxygen (O2).
4. Predict what will happen when you blow into the beaker. Record your prediction
on the Cellular Respiration Recording Sheet.
5. Pour the directed amount of indicator into a beaker. Place a straw into the
beaker and slowly exhale through the straw into the indicator. Be careful to not
drink or inhale the solution.
6. Record you observation on their Cellular Respiration Recording Sheet.
7. Design an experiment using the supplied materials to test and observe cellular
respiration. Draw and label the set up the Cellular Respiration Recording Sheet.
8. Within your groups discuss what you think will happen in this experiment and
develop your ideas to form a hypothesis. Record your hypothesis on the Cellular
Respiration Recording Sheet.
9. Place your beakers containing the test tubes in the sunlight for at least two hours
or until the next day.
Part 2
1. After at least one hour in the sunlight observe the test tubes and record your
observations on the recording sheet.
2. Discuss what is missing from the test tube that the Elodea needed. Answer
questions 8 on the recording sheet.
3. Review the chart you created at the beginning of the lesson. Using what you
knew and have learned about cellular respiration complete the Venn Diagram on
the recording sheet.
4. Compete review questions 10 & 11 on the recording sheet.
www.njctl.org 5th Grade PSI Energy in Organisms
Cellular Respiration Recording Sheet Name:__________________________
5th Grade PSI
Photosynthesis Cellular Respiration Record Sheet
1. Original color of BTB solution: ________________________________________
2. Prediction: What will happen when carbon dioxide (CO2) is added to the
solution? _________________________________________________________
3. Observation: What happened when carbon dioxide (CO2) was added to the
solution?
________________________________________________________________
________________________________________________________________
________________________________________________________________
4. Draw and label test tubes
Test tube #1 (with elodea) Test tube #2 (without elodea)
5. Hypothesis: If we put the test tubes into the sun __________________________
________________________________________________________________
because_________________________________________________________
________________________________________________________________.
www.njctl.org 5th Grade PSI Energy in Organisms
6. Draw and label test tubes
Test tube #1 (with elodea) Test tube #2 (without elodea)
7. Observation (after one hour in sunlight):
Cause Indicator Change Explanation
Carbon Dioxide
Elodea + solution + Sunlight
Solution + sunlight
www.njctl.org 5th Grade PSI Energy in Organisms
8. What would happen to the water with the Elodea if a snail was added into the test
tube? What would it contribute that the plant might need?
________________________________________________________________
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9. Label the let Photosynthesis and the right Cellular Respiration, in the middle write
Same, then complete the Venn Diagram:
www.njctl.org 5th Grade PSI Energy in Organisms
10. Conclusion: What do you think caused the changes in color? Keep in mind that
BTB indicator reacts with carbon dioxide.
________________________________________________________________
________________________________________________________________
________________________________________________________________
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11. What would happen if the elodea test tube was put in a dark closet instead of
sunlight? What color would the solution be and why?
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