Plants Grow from Air & Water
Support an argument that plants get the materials they need for growth chiefly from air and water, not from the soil
What a learner can do afterwards
- Explain that plants take in carbon dioxide from air and water from soil to make food (photosynthesis)
- Argue that most of a plant's mass comes from air (CO₂) and water, not soil minerals
- Describe a simple investigation showing soil mass barely changes while a plant grows significantly
The lesson
It looks like a plant grows by eating soil, the same way you grow by eating food. That is not quite right. A plant makes almost all of its own body out of air and water.
A scientist planted a small tree in a pot and weighed the soil first. He watered the tree for five years and let it grow. The tree became much bigger and heavier. But when he weighed the soil again, it had lost only a little weight, not nearly enough to explain the tree's new size.
Photosynthesis is the word for how a plant makes its own food. It takes in carbon dioxide from the air and water from its roots, then uses sunlight to turn them into sugar. That sugar becomes new leaves, stems, and roots.
A plant's body is mostly built from air and water, not from soil.
Watch it
Where it sits
This opens up
Where this leads
Jobs that lean on this skill. Follow one to see everything it is built on.
8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.