Class (Grade Level):
10th
Photosynthesis Lab—Sara Eick
Time Length:
60 minutes
“BIG IDEA” for LEARNERS
“How do humans gain energy from food? “ Organisms obtain and store energy for biological
processes (photosynthesis and cellular respiration)
LESSON OVERVIEW
The lesson starts with engaging in something they are all familiar with, candy. This is a
way to contextualize the lesson for the students by linking photosynthesis with something
familiar. Students will then be take part in a lab that will show them the process of
photosynthesis by using leaf disks and baking soda as a carbon source. Also, by having
students work in groups it will help them in the scientific discourse. The main focus of this
lesson is scientific sense making with the students. It gives students an opportunity to practice
speaking and using the academic language of biology. They can use the terms in regards to a
scientific discourse activity. Furthermore, it helps support their literacy and language
acquisitions by having them hear, read, write and speak.
After a short class discussion and review of photosynthesis, students will do the leaf
disk activity. The leaf disks will be placed in a bicarbonate solution (carbon source) and be
exposed to a light source (the sun). Students will monitor time for 15 minutes and record how
many disks are floating at each interval. Following the lab there will be a class discussion on
what happened during the lab. Students will change groups and think pair share about the lab
procedure and share their observations. During the group activity, students will be given a
poster board where they will create a compare/contrast graph or illustration of their
observations and the variables that were tested. These groups will then be asked quickly
present their information. A whole class discussion will be held about what evidence they saw
that supports the idea that photosynthesis occurred. The teacher will then have students finish
their lap write ups in the next class period.
STANDARDS
Next Generation Science Standards (NGSS)
HS LS1 5 Use a model to illustrate how photosynthesis transforms light energy into stored
chemical energy.
Arizona Science Standards
S4-C5-PO1 Compare the processes of photosynthesis and cellular respiration in terms of energy
flow, reactants, and products.
Arizona College and Career Readiness Standards (Literacy in Social Sciences, Sciences,
and Technical Subjects)
9-10.RST.4. Determine the meaning of symbols, key terms, and other domain-specific
words and phrases as they are used in a specific scientific or technical context relevant to
grades 9–10 texts and topics.
9-10.WHST.1. Write arguments focused on discipline-specific content.
LESSON LEARNING OBJECTIVE AND ASSESSMENT
Students will be able to explain photosynthesis via evidence based inquiry by preforming “leaf
disk” experiment.
Students will demonstrate their understanding of photosynthesis by conducting “Leaf Disk
Lab” with different variables to infer based on evidence the process of photosynthesis. They
will then do a lab write up the will be critiqued based upon rubric.
SCIENTIFIC PRACTICES AND ASSOCIATED LANGUAGE FUNCTIONS
SCIENTIFIC
PRACTICE(S)
Planning and carrying out investigations
Analyzing and Interpreting Data
Obtaining, Evaluating and Communicating Data
Scientific Explanation
RECEPTIVE
LANGUAGE
FUNCTIONS
Comprehend descriptions of variables and resources
Read and follow investigative plan
Interpret questions from others about the data
Read or listen to obtain scientific information from diverse sources
including lab or equipment manuals, oral and written presentations of
other students, Internet materials, textbooks, science oriented trade books
and science press articles
PRODUCTIVE
LANGUAGE
FUNCTIONS
Make predictions
Describe observations
Respond to question by amplifying explanations
Communicate (orally and in writing) ideas, concepts, and information
related to scientific information.
KEY VOCABULARY
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[List both key content and inquiry vocabulary]
Photosynthesis
Energy
Carbon Dioxide
Glucose/Sugar
Light Dependent
Light Independent
ATP
NADHP
Chloroplast
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Hypothesis
Independent/Dependent Variables
MATERIALS
 Copies of lab packet that include: lab procedure, questions, data tables, writing prompts and blank
graphing paper
Baking Soda
 Leaf Samples
50 ml beakers
Light Sources
Clamps
Timers
20 cc syringes
Hole punchers
Markers
Pipets
RESOURCES
http://www.elbiology.com/labtools/Leafdisk.html
http://www.bozemanscience.com/science-videos/2011/11/30/photosynthesis-labwalkthrough.html
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PREREQUISITE KNOWLEDGE
Students will have learned about the different organelles of plant and animal cells.
Students have been introduced to the process of cellular respiration.
Students will recall their lesson on the process of photosynthesis.
Lab procedures and safety.
TEACHING PROCEDURES AND ANNOTATED SSTELLA PRACTICES
Engagement
As students walk into the room they will be given
a piece of candy. There will be a warm up
question on the board: What is your favorite kind
SSTELLA Practices
The teacher helps the students by relating
the process of photosynthesis to a piece of
candy that contains sugar
of candy? What happens to you after you eat it?
Why do you think so? The students will have 1 to
2 minutes to think or write down their answers.
The teacher ask students to share out their
responses. The teacher will remind students of
the Big Idea of “How do we get energy from
food?” The students will be then asked simply
“How does our food make its own food?” (How
do autotrophs make their own energy?) Another
brief class discussion will follow. The previous
day’s homework, was for students to bring a type
of leaf from home that will be used in the lab for
the day and ask them to get out their samples.
This was a way to make photosynthesis more
relatable to the students by showing them that the
process occurs all around them, even in their own
backyards. If there are students that did not bring
any in, the teacher will provide it for the lab. The
teacher will do a brief overview of photosynthesis
chemical reaction. The teacher will then have
students watch a brief video of photosynthesis to
review before lab. Also, ask them to keep in
mind the idea of energy. As a transition, the
students will be asked if they have enough energy
from the candy to do a lab.
(contextualization). The teacher asks
students to participate in class by engaging
with them in a guided discussion. If
needed the teacher will adapt the questions
in response to how the students answer.
6CO2 + 6H2O + energy --> 6O2 + C6H12O6
http://www.youtube.com/watch?v=C1_uez5WX1o
The teacher will then scaffold the lab
procedures with the students by having modeling
and going over the instructions. Also, ask for
“Thumbs up/down” on their understanding of
instructions. There will be a handout with simple
step by step instructions with illustrations.
Students will be placed in groups and given tasks
to perform.
Exploration
Students will have been briefed on the lab at the
end of last class period. The previous days task
given at the end of class was for students to bring
in a “sample” leaf from home or surrounding
The teacher is having students investigate
the process of photosynthesis by observing
the leaf disks in baking soda solution
(sense making).
area. Students will be told to get into their lab
groups. Students will be given tasks: time keeper,
data recorder, mixer and solution preparer. The
teacher will then go through and model the lab
with the students. First students will see the
varying type of leaf disks, containers with water
and baking soda solution, syringes and timers on
their tables. Hole punchers will be provided to
cut out the leaf disks for the samples brought
from home. Students will remove plunger from
syringes and place 20 leaf disks into syringe.
Replace the plunger and fill with baking soda
solution. Teacher will tell students not to fill all
the way. The disks should be floating at this time.
Hold syringe tip up and expel the air. Cover the
end of the syringe with fingertip and pull plunger
and hold for 15 seconds. This will remove the air
from the leaf disks. Do this procedure until all
leaf disks sink. Expel excess fluid from syringe.
Place 10 disks in each container. Place both cups
under the light source and turn it on. As soon as
light is on, timers start. Students will observe at
one minute increments for 15 min how many
disks will float. Big question we are trying to
answer “Can plants make food from baking
soda?” Remember reaction. They are using a
carbon source to produce oxygen. When the O2 is
produced the disks will float.
Explanation
After lab is completed the teacher will lead a
class discussion on what they observed and why
they think the disks floated. The teacher will
again ask students to keep in mind the reaction
that is written on the white board. Answers will
be recorded on the board. Based on students’
answers, the teacher will adapt the questions to
elicit the answer. The explanation is when the
baking soda (carbon source) placed into the leaves
it changed the density and when they were
places in the solution the light caused the oxygen
to be released making the disks to rise. There are
other variables that will be added to the lab to see
what can change the rate of the floating leaf disks.
This will allow students to share with their
peers how this activity applied to
photosynthesis based on their observations
(science discourse) and defend why they
have this point of view.
By the teacher giving students this lab
they can relate what they learned about
photosynthesis to a visual representation of
how the process works (contextualized
science activity).
In the after lab discussion the teacher will
facilitate by scaffolding the discussion. The
teacher will lead questioning and have students
participate in instructional conversation. Did the
thickness of the leaves have any effect on the rate?
If needed the teacher will paraphrase what the
students are responding with. Also, ask them to
elaborate/add to their answers. If needed give
students wait time to help them process the
question that is being asked. There will be
various leaf materials and different concentrations
of sodium bicarbonate. The teacher will then
have students switch to other groups to think pair
share what evidence they saw that supports the
hypothesis of the oxygen being released. The
teacher will give the students about 5 minutes to
share with the group. During the think pair share
students will be given a graphic organizer (poster
board) where they will be able to write their
observations down comparing and contrasting
the different variables. Students will then be
asked to come to the front of the class and share
out their poster boards what they saw and the
differences between the variables.
Extension
Students will then return to their lab groups.
The teacher will engage students in a discussion
looking at the different poster boards. Was there
evidence of photosynthesis? If there was what
was it? (Floating disks). In the chemical reaction,
there needed to be a carbon source. What is it?
Did the different concentrations have an effect on
the number of disks? If there was weird data,
what could account for it? Could it have been
laboratory error? Being able to show that science
isn’t a pretty process and there you will get data
that doesn’t make sense, is a way to contextualize
the scientific process to the students.
By letting student add and discuss how the
experiment could be changed, it helps
them understand that there are other
factors that can change experimental
results (science discourse). They can also
see what the other students observed with
the compare/contrasting poster boards.
Evaluation
Students will be assessed throughout the activity.
There will be class discussions to assess their
This is where students will be able to put
into writing what they have learned about
photosynthesis and the lab (language and
understanding of the material. Also, students will
be informally assessed by their share outs of the
compare/contrast of their observations. The
teacher will also walk around and monitor during
the activity and ask each group if they have any
questions or need clarification.
For the formative assessment students will turn in
their lab write up and be graded by a rubric that
they all have copies of.
literacy).
Appendix A
1. What causes the disks to float?
2. What is the dependent variable
3. What is the independent variable?
4. After graphing the time and number of disks, where did the most disks float?
5. What is the purpose of the baking soda?