Serendip is an independent site partnering with faculty at multiple colleges and universities around the world. Happy exploring!

Where does a tree's mass come from?

4 hypotheses where plant's mass comes from

Students analyze evidence to evaluate four hypotheses about where a tree’s mass comes from. For example, students analyze Helmont’s classic experiment and evaluate whether his interpretation was supported by his evidence.

Thus, students engage in scientific practices as they learn that trees consist mainly of water and organic molecules and most of the mass of the organic molecules consists of carbon and oxygen atoms that came from carbon dioxide molecules in the air. (NGSS)

The Student Handout is available in the first two attached files and as a Google doc designed for use in distance learning and online instruction. (For additional instructions, see, especially item 7.) The Teacher Notes, available in the last two attached files, provide instructional suggestions and background information and explain how this activity is aligned with the Next Generation Science Standards.

PlantMassFromSHO.docx2.11 MB
PlantMassFromSHO.pdf464.65 KB
PlantMassFromTN.docx1.86 MB
PlantMassFromTN.pdf781.31 KB


Golda's picture

How long did this take

How long did this take people's classes?

iwaldron's picture

Guesstimate of how long it takes

How long this activity will take depends on your students, their prior learning, and whether you give them time to work through the questions (in pairs) before a whole class discussion of the questions (see Teacher Notes). I would guess that this activity will take approximately 30-50 minutes.


iwaldron's picture

2022 revision

I have improved the logical flow of the Student Handout, clarified many of the questions, and added two new figures.

iwaldron's picture

September 2017 revision

The Student Handout has been revised to incorporate more analysis of experimental evidence and to improve logical flow and clarity.


iwaldron's picture

2017 revision

Additional figures and substantially revised questions in the Student Handout will help students better understand the reasoning and the important concepts (including the relevant NGSS Disciplinary Core Ideas and Crosscutting Concepts).

iwaldron's picture

2016 revision

These revisions have improved clarity and accuracy.

iwaldron's picture

2014 revision

The questions in the Student Handout have been clarified so students can more readily think through the logical flow of the argument. The revised Teacher Notes have improved suggestions for teaching this activity and enhanced background information and also clarify the alignment of this activity with Next Generation Science Standards.

Logan mannix's picture


Thanks for the help

iwaldron's picture

Revised Version of Student Handout

This revised student handout provides a more complete set of questions to help students evaluate each of the hypotheses concerning where a plant's organic mass comes from.  In addition, the wording and logic of the questions has been clarified.

Post new comment

The content of this field is kept private and will not be shown publicly.
To prevent automated spam submissions leave this field empty.
7 + 5 =
Solve this simple math problem and enter the result. E.g. for 1+3, enter 4.