Tiny seedlings grow and transform into trees with a great quantity of matter.
Conduct an investigation to produce data to explain that carbon dioxide gas is involved when plants matter (live and grow).
The amount of carbon dioxide in the water surrounding aquatic plants increases and decreases depending on the amount of light.
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In this lesson, students will build on the learnings from the previous lesson that plants need sunlight to add mass, but soil and water are not part of the additional mass. In this lesson, students investigate the gases that are exchanged within the plant. They will continue to use models to explain their thinking about the phenomenon, extending their models to include components too small to be seen (invisible). Students will plan and conduct another investigation by building on their understanding of variables and tools from the previous lesson to plan and conduct the investigation. Students will apply the concept of stability and change to think about how changing the inputs in one part of the system (amount of light, amount of CO2), affect other parts of the system as they analyze evidence collected from their investigations.
Throughout the lesson, a flag () denotes formative assessment opportunities where you may change instruction in response to students’ level of understanding and making sense of phenomena.
Part I | 60 minutes | Explore |
Part II | 60 minutes | Explain |
Conduct an investigation to collect data on observable and unobservable variables to explain how trees rearrange carbon dioxide and water into complex molecules to support growths.
This is another opportunity to assess what students understand about the crosscutting concept of Energy and Matter, similar to the assessment in Lesson 7.3: Historical Investigations. New aspects to consider in this lesson include: Does the model include a representation that matter is made of particles? Are students thinking about the amount of matter before, during, and after the process? Do they include energy in different forms? If they do not, you may want to consider pausing the sequence here and returning to previous lessons on matter taught prior to this sequence. Students may need an opportunity to reconnect with these concepts via a brief review of their science notebook, additional reading or video, or brief small group discussion.
You will want to review safety procedures with the class prior to starting the investigation. Important safety issues to reinforce basic safety rules include do not put any materials in your mouth, wear goggles when working with liquids, and use care when using glassware. You should have a special container to collect any broken glass so it is not placed in the classroom trash can. Bromothymol blue is a relatively safe chemical, but you should review the material safety data sheet prior to using it: http://www.labchem.com/tools/msds/msds/75033.pdf.
BTB is an indirect indicator that CO2 is present. BTB is normally blue (as the name indicates), but when CO2 is added, it will cause the BTB to change to green, and with increasing amounts of CO2, to yellow. When CO2 is taken out of a BTB solution, the color change reverses back toward blue. For English Learners, it is useful to have a visual reminder of terms such as CO2 on a yellow card, some CO2 on a green card, and no CO2 on a blue card.
This is an opportunity to differentiate for students progressing more rapidly or slowly with the SEP through the complexity of the investigation design. Since students will conduct this investigation, the sophistication of data collected, and the complexity of the design can be adjusted. For example, some groups may want to collect data of multiple variables (multiple set-ups) or run part of the investigation outside of the classroom.
Analyze and interpret data to provide evidence for how trees rearrange carbon dioxide and water into complex molecules to support growth.
The intent is not to “correct” students’ models but to provide guidance that will help students reflect on their model and provide suggestions for things they may have not considered. When you return the feedback to students, tell them to read the feedback and consider what they could use to improve their models. Tell them if something in the feedback is unclear, they should ask you for clarification. Remind students that the feedback is intended to be useful and is not an indication of a good or bad model.
California Department of Education. (2014). Science Safety Handbook for California Public Schools. Retrieved from https://www.cde.ca.gov/pd/ca/sc/documents/scisafebook2014.pdf
FOSS, & The Regents of the University of California. (n.d.). Science-Centered Language Development. Retrieved from https://www.fossweb.com/delegate/ssi-wdf-ucm-webContent?dDocName=D56715
LabChem.com (n.d.). Material Safety Data Sheet. Retrieved from http://www.labchem.com/tools/msds/msds/75033.pdf