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Lesson Overview
Lesson Overview
Guiding question: What is the relationship between plants, animals, and carbon dioxide?
Time Estimate: 50 minutes
Purpose: Gather evidence that burning fossil fuels and cellular respiration increase the amount of CO2 in the atmosphere, while photosynthesis decreases the amount of CO2 in the atmosphere.
Overview: Using CO2 detectors, students will track how levels of CO2 in the air change as they breathe, during the burning of a candle, and during the photosynthesis of spinach leaves.
Design Principles:
Science investigation
Argumentation
Modeling
Background Knowledge: Students might enter with ideas about cellular respiration (breathe in oxygen, breathe out carbon dioxide). They may not call it cellular respiration, but the general concept should not be new from elementary and 6th grade curricula.
Common Misconceptions: Plants only take in carbon dioxide and release oxygen: Students may oversimplify the process of photosynthesis, thinking that plants only absorb carbon dioxide and release oxygen, without understanding the complex biochemical pathways and other substances involved in the process.
Safety: Lighting a candle is restricted to a designated area and can only be performed by the teacher.
Unit Connections: connects to water use in U, Israel, India, and Cote D’lvoire (Ivory Coast)
📂 Materials
📂 Materials
Teacher
1 CO2 detector (make sure it is charged ahead of time)
Gallon bag
Spinach leaves (pre-soaked in water works best)
Lamp (with grow lights) or access to a window with sufficient sunlight
Student
A way to add their CO2 models if they are maintaining personal ones
The Story of Oil card sort (cut and mixed up) 1 per group
Quiz-Quiz-Trade cards (the set has 24 questions, add additional ones if the class is bigger)
Optional
If you want to redo the burning candle demonstration: a candle and matches
Some type of whiteboard or chart paper to track CO2 levels
Instructional Sequence
Instructional Sequence
This lesson’s instructional sequence is broken down into two segments. For the first 10-15 minutes, we are using the CO2 sensor to monitor the carbon dioxide concentration of human respiration. The remaining time is for monitoring what happens with photosynthesis and drawing conclusions from the data collected.
Materials: Slide Deck: 2.1 Oxygen & Carbon Dioxide, CO2 sensor
Part 1: Human Respiration and CO2
Lesson starter (slides 1-3)
Burning fossil fuels uses oxygen and emits carbon dioxide. Pose the question: What else do you know of takes in oxygen and releases carbon dioxide? Students should be able to identify that humans and animals breathe out oxygen and release carbon dioxide.
Respiration emits carbon dioxide
Slides 4-12: Review the components of the CO2 sensor (slides 4-5) and use students’ prior knowledge to ask what will happen when someone breathes on the CO2 sensor.
We recommend having a chart similar to the one on below (slide 6) on a whiteboard or a piece of chart paper that you can refer to and fill in as the class progresses. Record the reading of the sensor for the first time in the table.
Example:
⏰ Depending on timing and classroom structures, this lesson might need to be modified to be split into two days. If that is the case, we recommend using the “what is a value of a tree?” activity from lesson 2.2 to fill in remaining time.
⏰ Make a chart on your whiteboard or chart paper to fill in throughout the class period. Or you can fill it in throughout the day and extend data analysis to analyze the full day.
Inform the class that we will be recording the changes in CO2 concentration in our classroom during this class. Ask the class what they predict will happen as the class goes on.
We expect students to know that the CO2 concentration will increase, so move on to slide 9 to demonstrate why that might be.
Check the CO2 sensor again because, at this point, it has had time to read the correct level. (slide 10)
Materials: Quiz-Quiz-Trade cards
While you wait, do a quick game of Quiz-Quiz-Trade.
Instructions:
Prepare Cards
Have students pair up
Use the stand up/hands up/pair up method for students to find a partner. Partner A asks their question (be sure to have them cover the answer). Partner B answers. Partner A praises if correct or coaches if incorrect. They switch roles and Partner B asks Partner A the next question.
Hands Up
After thanking each other and switching cards, Partners A and B raise their hands to find a new partner and repeat the process for an allotted amount of time.
This activity provides a chance for multiple people to be talking at once and gets students up and moving. It will help the CO2 sensor go up faster. The questions are a review of lesson set 1.
Check the CO2 sensor for a third time (slide 12): After the rock, paper, scissors activity, check the CO2 sensor a final time. Ask students about what conclusions we can draw from the data.
Students should be able to say that the CO2 concentration went up, especially when we were moving around.
This means that humans contribute to the concentration of CO2 in the atmosphere by breathing.
Adding to our models:
Using the data and conclusion you just reached from the CO2 sensor, ask students how they can represent this new piece in their models.
Students will then draw an arrow from the cows to the CO2 circle (slide 14)
Design Principle: Modeling
Part 2: Plants & Carbon Dioxide
Slide 15 helps you transition to the next part of the lesson: Do we know any processes that absorb CO2?
Next, we are going to collect data on what happens when we place spinach leaves in a gallon bag with the CO2 sensor and access to sunlight.
Procedures
Soak the spinach leaves in water for several minutes before the lab (do it before class).
Dab the spinach leaves with paper towels to gently absorb excess moisture from the leaves and put a handful of them into the gallon bag. Make sure the adaxial surface (the upper side) is facing up.
Turn on the sensor and wait till the number is NOT 500. (500 is the default number when it turns on). Then place the sensor in the gallon bag with the leaves. Seal the bag.
When the reading of the sensor gets stable, place the bag under the light. Then record the number.
Add a row to your previous chart, example below (slide 17), and record your initial CO2 concentration.
Have students predict what they think will happen to the CO2 concentration. (slide 18)
⏰ This activity provides a chance for multiple people to be talking at once and gets students up and moving. It will help the CO2 sensor go up faster. The questions are a review of lesson set 1.
✅ DP: Modeling
⏰ It might be helpful to already have this ready if you’re feeling short on time.
Check the CO2 again (slide 19)
It might be helpful to already have this ready if you’re feeling short on time.
Materials: The Story of Oil (one per group)
While waiting before the final CO2 check, students can use this time (~10 minutes) to tell the story of oil. The cards are in the correct order in the slides, so be sure to mix them up before giving them to students.
The activity on slide 20 is a time filler while we wait for the spinach to do photosynthesis. Feel free to change this activity to fit your needs.
This can also be a good time to complete unfinished assignments, and those who do not have missing work can do the story.
Check the CO2 sensor a final time
Ask students if their predictions were correct (slide 22). We expect them to be correct, so use students’ prior knowledge that led them to make a correct prediction to ask what it is that plants are doing that caused the CO2 concentration to decrease (slide 23).
Ask the students, “what did we put in to the system and what did we get out?” (slide 24)
We expect students to come up with the following:
Carbon Dioxide went in
Sunlight went in
Oxygen came out
Then ask students what else we know that plants need to really grow (slide 25). And add water to the picture (slide 26).
Lastly, tell students that photosynthesis also produces carbon compounds, which the plants use to grow in size (slide 27).
⏰ The activity on slide 20 is a time filler while we wait for the spinach to do photosynthesis. Feel free to change this activity to fit your needs.
This can also be a good time to complete unfinished assignments, and those who do not have missing work can do the story.
⏰ Students can do this in groups or you can facilitate a whole class discussion.
📒 Instructional support
📒 Instructional support
Students can do this in groups or you can facilitate a whole class discussion.
Closing
Slide 28: Have students summarize the relationship between the two processes explored today.
Example sentences:
Animals and plants have opposite processes that affect the CO2 concentration differently. Humans and animals breathe in oxygen and out carbon dioxide, which contributes to the CO2 concentration in the atmosphere. Plants take in carbon dioxide and release oxygen, which reduces the CO2 concentration in the atmosphere.
Summarize that the processes are opposite, and have students add photosynthesis to their models.
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