Investigating Photosynthesis

Type Category
Instructional Materials
Activity , Experiment/Lab Activity
This resource, vetted by NSTA curators, is provided to teachers along with suggested modifications to make it more in line with the vision of the NGSS. While not considered to be “fully aligned,” the resources and expert recommendations provide teachers with concrete examples and expert guidance using the EQuIP rubric to adapted existing resources. Read more here.



Students design and conduct simple experiments using elodea (aquatic plant sold in pet stores) and Bromthymol blue to determine whether plants consume or release carbon dioxide in the process of photosynthesis. Students will record their data which will be used to conclude whether carbon dioxide was consumed or released by the elodea. Through class discussion of student data, students will learn that carbon dioxide was consumed during photosynthesis.

Intended Audience

Educator and learner
Educational Level
  • Grade 8
  • Grade 7
  • Grade 6
  • Middle School
Access Restrictions

Free access - The right to view and/or download material without financial, registration, or excessive advertising barriers.

Performance Expectations

MS-LS1-6 Construct a scientific explanation based on evidence for the role of photosynthesis in the cycling of matter and flow of energy into and out of organisms.

Clarification Statement: Emphasis is on tracing movement of matter and flow of energy.

Assessment Boundary: Assessment does not include the biochemical mechanisms of photosynthesis.

This resource appears to be designed to build towards this performance expectation, though the resource developer has not explicitly stated so.

Comments about Including the Performance Expectation
The teacher should allow students to make some close observations of the elodea as it goes through photosynthesis. Ideally, this will be done in small groups. Also, if students have not already learned conservation of energy, it may be difficult for them to trace the flow of energy. That part of the PE could be addressed by using molecular models and discussing the energy that molecules store in their bonds. One caution: Elodea is an invasive species! Do not release it into local waterways.

Science and Engineering Practices

This resource is explicitly designed to build towards this science and engineering practice.

Comments about Including the Science and Engineering Practice
The students will need to consider the role of the indicator in the observations. Many students would not have seen an indicator previously, so they may need some clarification of its role. The ideal setup would allow small groups to set up their own samples, both covered with foil and uncovered. This will allow small groups to have access to the samples as they discuss their explanations. Also, diagramming of the the inputs and outputs of the system within the test tube would make it more concrete to some learners. The best approach to writing a conclusion like this would be to use the Claims, Evidence, Reasoning (CER) format. As an extension, this could be used as a student-centered activity with the students developing their own questions to test and following through with observations and explanations.

Disciplinary Core Ideas

This resource appears to be designed to build towards this disciplinary core idea, though the resource developer has not explicitly stated so.

Comments about Including the Disciplinary Core Idea
If students are not yet familiar with chemical processes, this DCI could be illustrated through the use of molecular models to show the rearrangement of particles to create new substances through chemical reactions. If students have already studied chemical reactions, the teacher could ask them to determine the number of molecules of each substance needed to produce the reaction.

This resource is explicitly designed to build towards this disciplinary core idea.

Comments about Including the Disciplinary Core Idea
By using examples of other plants, the teacher can develop the understanding of sugars being stored for later use (apples store sugar around their seeds so the seeds get energy to eventually start a new plant). Students could also investigate what plants contribute the most to the oxygen in our atmosphere (algae!) so they do not only associate oxygen production with land plant species.

Crosscutting Concepts

This resource appears to be designed to build towards this crosscutting concept, though the resource developer has not explicitly stated so.

Comments about Including the Crosscutting Concept
Although the idea of energy transfer driving the cycling of matter is the central idea to this activity, the students will not see this as the Cross Cutting Concept unless the idea is developed through discussion. After the students have diagrammed the system and the teacher is satisfied with their understanding of what happened, the teacher needs to explicitly question the students, either in small groups or as a class discussion, about the reason for the cycling of matter. This is a point where the teacher needs to work to deepen the students understanding that the sunlight is the trigger for the reaction between the molecules.

Resource Quality

  • Alignment to the Dimensions of the NGSS: This activity can be better aligned to NGSS by making sure the students are actively engaged in observing and creating the explanations of the phenomena and the teacher is leading them to the understanding of the DCIs and the CCC through questions that help them to reason the ideas.

  • Instructional Supports: There is a student handout provided on the website, but it would be recommended to make your own that is more open-ended so that the students are not guided to an answer, but form their own explanations.

  • Monitoring Student Progress: The monitoring of student progress is up to the teacher throughout this activity. As students are making observations and having small group discussions, teachers should be eliciting more information from the students to get an idea of their understanding of the phenomena. Since this activity will take several days, the teacher could use exit tickets, etc. to do a periodic check of each student.

  • Quality of Technological Interactivity: - none -