Where a Plant's Mass Comes From
A 60-minute Grade 5 lesson on supporting the argument that plants get the materials for growth chiefly from air and water.
Where a Plant's Mass Comes From is a free 60-minute Grade 5 science lesson plan for Common Core standard 5-LS1-1 — argue that plants build themselves mostly from air and water. It is timed across 5 sections, gives the exact wording to use where the wording carries the mathematics, names 3 misconceptions with the teaching move that addresses each, and ends with an exit ticket and a printable worksheet with its answer key.
- Grade:
- Grade 5
- Length:
- 60 minutes
- Standard:
- 5-LS1-1
Grade 5 · Life Science
5-LS1-1
Support an argument that plants get the materials they need for growth chiefly from air and water.
Objective
Students will be able to use mass data to argue that a plant's material does not come mostly from soil.
Students are successful when they can
- Compares the plant's gain with the soil's loss.
- Concludes air and water rather than soil.
- Says what the soil does supply.
What you need
- The five-month potted plant record, a balance, dry soil samples
- A class plant to weigh and set up for a long-run measurement
- The printable practice sheet linked at the end of this plan
The lesson
Warm-up
5 min- Ask where the mass of a large tree came from.
- Take 'the soil' and write it up as the hypothesis to test.
Teach — the numbers rule the soil out
15 min- Read the record: plant gained 474 g, dry soil lost 12 g.
- Ask what the soil hypothesis predicts. A soil loss close to 474 g.
- Compare with what happened. The prediction fails.
- Ask what is left: air and water, both freely available to the plant.
- Say what the soil does supply: water and small amounts of minerals.
- Note why the soil was dried before weighing: water in it would swamp the change.
“If it came from the soil, what should the soil have lost?”
Investigate — set up a long run
22 min- Groups weigh a seedling and its dried soil separately and record both.
- They set up the pot, agree a watering measure and a review date.
- They write the prediction each hypothesis makes.
- They say which measurement will distinguish the two.
Independent practice
15 min- Students complete the 'Where a Plant's Mass Comes From' page.
- Check answers use both figures, not one.
Close
3 min- Ask what a hydroponic plant grown with no soil at all would show.
What goes wrong, and why
Each of these is a reasoning error rather than carelessness. The fix addresses the reasoning.
Says plants eat soil.
Why: Roots are in the soil.
Fix: The soil lost 12 g and the plant gained 474 g.
Thinks water alone accounts for the gain.
Why: Plants are watered a lot.
Fix: Much of it evaporates. Carbon dioxide from the air supplies most of the solid material.
Weighs damp soil.
Why: It is the soil in the pot.
Fix: Water in the soil changes the reading without any material being used. Dry it first.
If they are not there yet
- The two figures supplied, with the conclusion to write.
- A prediction frame for each hypothesis.
If they finish early
- Design a test using a plant grown without soil.
- Explain where a tree's carbon comes from.
- Say what measurement would falsify the air-and-water claim.
Exit ticket
A plant gained 474 g while the dry soil lost 12 g. What does that show, and what does the soil supply?
What to look for: The mass came chiefly from air and water, not soil; the soil supplies water and minerals. Using one figure means the comparison needs another run.
Printable practice for 5-LS1-1
Free to print and copy, answer key included. Each sheet can generate a fresh set of problems for a retake.
- Where a Plant's Mass Comes FromRead the record, then answer the questions.
Questions about Where a Plant's Mass Comes From
How long does the Where a Plant's Mass Comes From lesson take?
60 minutes, split across 5 timed sections: warm-up 5 min, teach 15 min, investigate 22 min, independent practice 15 min, close 3 min. The minutes are stated per section and add up to the stated length, so the plan can be cut or extended at a section boundary rather than abandoned halfway.
Which standard does Where a Plant's Mass Comes From teach?
5-LS1-1 — 5-LS1-1, Life Science for Grade 5: “Support an argument that plants get the materials they need for growth chiefly from air and water.” In plain terms, argue that plants build themselves mostly from air and water.
What do I need to teach this lesson?
The five-month potted plant record, a balance, dry soil samples, a class plant to weigh and set up for a long-run measurement and the printable practice sheet linked at the end of this plan. Everything listed is either ordinary classroom equipment or a free printable from this site — there is nothing to buy and nothing to prepare beyond photocopying.
What mistakes should I expect in this lesson?
Three, each a reasoning error rather than carelessness: says plants eat soil; thinks water alone accounts for the gain and weighs damp soil. The plan gives the thinking behind each one and the teaching move that addresses the thinking rather than the symptom.
How do I know whether the lesson worked?
The exit ticket asks: “A plant gained 474 g while the dry soil lost 12 g. What does that show, and what does the soil supply?.” The mass came chiefly from air and water, not soil; the soil supplies water and minerals. Using one figure means the comparison needs another run. That tells you whether the class needs a reteach or a thirty-second conversation before you plan tomorrow.
Is there a worksheet to go with Where a Plant's Mass Comes From?
Yes — 1 printable 5-LS1-1 worksheet, linked at the end of the plan and free like the rest of the site. Each one comes with an answer key and 25 versions, so the practice after the lesson can be a different paper on every desk.
Is Where a Plant's Mass Comes From free to use?
Yes. The plan, its printables and their answer keys are free to read, print and photocopy for your own class, with no account and no email capture. It was last reviewed on 8 September 2026. Please do not resell it or republish it as your own.
Last reviewed 2026-09-08. Aligned to 5-LS1-1 of the Next Generation Science Standards.