2-Day Digital Lab Using BTB Indicator, CER Writing, and Equation Modeling.
This two-day digital investigation guides students through experimental analysis to determine when photosynthesis and cellular respiration occur and how the two processes interact.
Students begin by observing bromothymol blue (BTB) indicator changes in the presence of carbon dioxide. They analyze light and dark experimental conditions involving tap water, soda water, elodea, and snails to infer which variables influence each biological process.
Throughout the investigation, students construct Claim–Evidence–Reasoning (CER) explanations based on observed results, building a structured understanding of how light and carbon dioxide drive photosynthesis and how organisms produce carbon dioxide through respiration.
Students:
Interpret BTB color-change data under controlled light conditions
Determine which experimental setup demonstrates photosynthesis
Write CER conclusions explaining the role of light and carbon dioxide
Examine historical evidence that identified chloroplasts as the site of photosynthesis
Model the photosynthesis equation using molecular representations
This portion of the lesson emphasizes evidence-based reasoning and connects experimental results to cellular structure.
Students then analyze a second set of experimental conditions involving snails and elodea. They:
Form hypotheses about expected outcomes
Interpret experimental results
Construct CER explanations describing carbon dioxide production
Examine historical investigations that identified mitochondria as the site of respiration
Model the cellular respiration equation visually
Students also clarify a common misconception: plants perform both photosynthesis and cellular respiration.
The lesson concludes with a direct comparison of the two chemical equations. Students analyze how photosynthesis and cellular respiration function as complementary processes within cells and ecosystems.
By the end of the investigation, students understand:
The conditions required for photosynthesis
How respiration produces carbon dioxide
The role of chloroplasts and mitochondria
How the two processes operate in tandem within biological systems
This lesson supports experimental reasoning, CER writing, and systems-level understanding of cellular energy processes.
To see a preview of this lesson, click here.
NGSS Alignment (High School):
HS-LS1-5; HS-LS1-7; HS-LS2-3
NGSS Alignment (Middle School):
MS-LS1-6; MS-LS2-3
Science & Engineering Practices (SEPs):
Developing and Using Models
Analyzing and Interpreting Data
Constructing Explanations
Engaging in Argument from Evidence
Crosscutting Concepts (CCCs):
Cause and Effect
Systems and System Models
Energy and Matter
Stability and Change
Common Core (Literacy in Science):
CCSS.ELA-LITERACY.WHST.6-8.1 / WHST.9-10.1; CCSS.ELA-LITERACY.RST.6-8.7 / RST.9-10.7
2-Day Digital Lab Using BTB Indicator, CER Writing, and Equation Modeling.
This two-day digital investigation guides students through experimental analysis to determine when photosynthesis and cellular respiration occur and how the two processes interact.
Students begin by observing bromothymol blue (BTB) indicator changes in the presence of carbon dioxide. They analyze light and dark experimental conditions involving tap water, soda water, elodea, and snails to infer which variables influence each biological process.
Throughout the investigation, students construct Claim–Evidence–Reasoning (CER) explanations based on observed results, building a structured understanding of how light and carbon dioxide drive photosynthesis and how organisms produce carbon dioxide through respiration.
Students:
Interpret BTB color-change data under controlled light conditions
Determine which experimental setup demonstrates photosynthesis
Write CER conclusions explaining the role of light and carbon dioxide
Examine historical evidence that identified chloroplasts as the site of photosynthesis
Model the photosynthesis equation using molecular representations
This portion of the lesson emphasizes evidence-based reasoning and connects experimental results to cellular structure.
Students then analyze a second set of experimental conditions involving snails and elodea. They:
Form hypotheses about expected outcomes
Interpret experimental results
Construct CER explanations describing carbon dioxide production
Examine historical investigations that identified mitochondria as the site of respiration
Model the cellular respiration equation visually
Students also clarify a common misconception: plants perform both photosynthesis and cellular respiration.
The lesson concludes with a direct comparison of the two chemical equations. Students analyze how photosynthesis and cellular respiration function as complementary processes within cells and ecosystems.
By the end of the investigation, students understand:
The conditions required for photosynthesis
How respiration produces carbon dioxide
The role of chloroplasts and mitochondria
How the two processes operate in tandem within biological systems
This lesson supports experimental reasoning, CER writing, and systems-level understanding of cellular energy processes.
To see a preview of this lesson, click here.
NGSS Alignment (High School):
HS-LS1-5; HS-LS1-7; HS-LS2-3
NGSS Alignment (Middle School):
MS-LS1-6; MS-LS2-3
Science & Engineering Practices (SEPs):
Developing and Using Models
Analyzing and Interpreting Data
Constructing Explanations
Engaging in Argument from Evidence
Crosscutting Concepts (CCCs):
Cause and Effect
Systems and System Models
Energy and Matter
Stability and Change
Common Core (Literacy in Science):
CCSS.ELA-LITERACY.WHST.6-8.1 / WHST.9-10.1; CCSS.ELA-LITERACY.RST.6-8.7 / RST.9-10.7
