IT-E3 Tools Lesson
Created June 2009
Photosynthesis in Action
 Grade 6, 7 & 8
 Science
 1 Class Period
Authors:
Rachel Poland & Marj Atkisson
I. Standards
CA State Standards
Sixth Grade (Earth Science)
5. a. Students know energy entering ecosystems as sunlight is transferred by
producers into chemical energy through photosynthesis and then from organism
to organism through food webs.
5. b. Students know matter is transferred over time from one organism to others in
the food web and between organisms and the physical environment.
Seventh Grade (Life Science)
1d.Students know that mitochondria liberate energy for the work that cells do and
that chloroplasts capture sunlight energy for photosynthesis.
6f.Students know that mitochondria liberate energy for the work that cells do and
that chloroplasts capture sunlight energy for photosynthesis.
Eighth Grade (Physics)
5c. Students know chemical reactions usually liberate heat or absorb heat.
6c. Students know that living organisms have many different kinds of molecules,
including small ones, such as water and salt, and very large ones, such as
carbohydrates, fats, proteins, and DNA.
Nineth Grade:
1f. Students know usable energy is captured from sunlight by chloroplasts and is
stored through the synthesis of sugar from carbon dioxide.
6d. Students know how water, carbon, and nitrogen cycle between abiotic resources
and organic matter in the ecosystem and how oxygen cycles through photosynthesis
and respiration.
II. Objectives
Students will use the temperature probe and dissolved oxygen probe to understand
that plants use sunlight to do photosynthesis. They will know that:

Carbon dioxide is absorbed by plants and Oxygen is released

Sunlight (energy) is used as part of this process and can be measured as a
Temperature gain in the water.
III. Intro (3 min)
***Ask students to plug in probes***

What do you know about plants?

Brainstorming!

Tell me about photosynthesis.
IV. Vocabulary
Control
Photosynthesis
Chloroplasts
Autotroph
Respiration
CO2
O2
V. Materials/Supplies
LabQuest and Temperature and Dissolved Oxygen sensors
Grow lights (wide spectrum light bulb) or natural light outdoors
Straws
BTB (Bromthymal Blue)
Gallon Bag
Gatorade Bottles
Elodea (in bucket of water) NOTE: TEACHER MUST PURCHASE THIS AT A
LOCAL PET/AQUARIUM STORE; NOT SUPPLIED IN KIT!
Distilled Water
Advanced Prep:
NOTE: COS -rich water can be made by blowing into the water with a straw
Night Before: Place four samples (elodea in CO2 rich water) in a box – depriving it
of light until the experiment.
Day of Experiment:
At least one hour before the experiment place 4 more samples (elodea in CO2 rich
water) in the sunlight (best) or under the grow lights (may need more than one hour).
To keep the temperature more stable we would advise using a cool water bath so that
they do not over heat and cook the plants.
Make a solution of 20 drops BTB and about 100 ml of water – the mixture should be
a medium blue color (think Charger’s electric blue) because most tap water is
oxygenated. If you use distilled water it will be a greenish color to indicate a neutral
mixture.
Also, dissolved oxygen sensors need to be filled with solution.
VI. Procedure (you can use the powerpoint to guide the experiment)
1. Ask – What do we breath into our body?
What do we breath out of our body?
2. Do the Demo: (3 min)
a. Place the prepared BTB solution in the gallon baggie
b. Gather the bag around the end of the straw
c. Take a deep breath and hold for a few seconds
d. Breath out slowly through the straw to empty lungs
e. Use hand to seal the top of the bag and shake vigorously.
f. While shaking explain that BTB is an indicator and it changes color to
show oxygen or carbon dioxide. When it is blue – oxygen is present and
when it is yellow there is carbon dioxide.
3. Remind them that plants, opposite of how we breathe, use Carbon Dioxide to
make energy and release Oxygen as part of that process. We are going to look for
the Oxygen by using the DO sensor and comparing the results to a control (water
sample with no plants) and water sample with plants that have been deprived of
light (no photosynthesizing, only respiration).
4. Explain that they need to prepare their control water sample and make it rich with
Carbon Dioxide by blowing in the container with their straws.
5. Have students collect temperature data for each: control, plants out of light and
plants in light. Temperature should be close to the same. Ask students: why is
temperature important in this experiment? (Answer: cold water can absorb more
oxygen that warm water).
6. Use the probes to make a reading of the control and record it on their data sheet.
7. Pass out the plant samples and let them take readings of the plants from the
sun/grow light and the plants that were in the box.
8. Students should fill in their student data sheets.
EXTENSION – You can have the students use the pH probe in the O2 and CO2 rich
containers and in the different colored indicator solutions as well.
9. REMEMBER – to empty dissolved oxygen sensors and gently blot them dry
after the last use.
VII. Assessment
Ask the student to draw a diagram showing what is going into the plant
(sunlight & CO2) and what is being made (O2 and sugar).
VIII. Data Sheet
See Student Data Sheet that follows. Edit the sheet to include any of the
following questions based on your students and grade level.
Class collection sheet follows as well.
IX. Closure
Have students complete their data sheets.
X. Questions
6th Grade focus:
Based on what you learned why are plants important to the ecosystem?
How does O2 and CO2 cycle through an ecosystem?
How does sunlight initiate the flow of energy through the ecosystem?
7th Grade Focus:
Do plants need O2 and, if so, what do they use it for?
When do plants undergo photosynthesis?
What processes do plants do at night?
What process creates sugar and what process creates energy?
8th Grade Focus:
What chemical reaction is absorbing energy (from the sun) to bind
molecules?
What chemical reaction is liberating energy by breaking molecules?
Balance the chemical reaction for photosynthesis:
CO2 + H2O -> C6H12O6 + O2
9th Grade Focus:
How does oxygen cycle through photosynthesis and respiration?
Explain how a plant (like giant sequoia) is produced from the “air” it
absorbs. Hint: you should be explaining the carbon cycle. (May need to
add an additional slide to address this issue)
XI. Resources
Provided:
A power point – all photos are annotated and used without permission.
Student Data Sheet : Please edit to include your questions of choice.
Photosynthesis in Action
Student Data Sheet
Plant w/light
Dissolved Oxygen
(mg/l)
Sample values:
5.9
9.6
Temperature
(degrees C)
Sample values:
24.4
25.9
Plant in box
6.4
22.4
control
Draw a diagram in the space below that shows a plant doing
photosynthesis. Include the following labels: Carbon Dioxide,
Oxygen, Sunlight, Sugar
Class Data Collection Sheet
Dissolved Oxygen
Control
Group 1
Group 2
Group 3
Group 4
Group 5
Group 6
Group 7
Group 8
Light
Dark