1Two invisible deliveries reach a leaf
A leaf breathes in air and sips up water
Two things sneak into every leaf, and you can't see either one. Watch them arrive:
Carbon gas, from the air
The air is full of an invisible gas called CO₂ — carbon dioxide. A leaf breathes it in through tiny holes. The carbon inside it is the secret stuff trees are built from.
Water, from the soil
Roots sip up water and pump it all the way up to the leaves. The water brings the other half a leaf needs to build.
2Two ideas about where wood comes from
Does a tree eat the dirt, or drink the air?
Here are the two guesses people make. They can't both be right — watch how each one says the ground should change:
The "eats the dirt" idea
The tree sucks soil up its roots and turns it into wood — so the ground should sink lower as the tree grows.
The "drinks the air" idea
The tree builds its body from carbon caught in the air — so the ground should barely change as the tree grows.
3Your turn — feed the leaf
Snap the ingredients into sugar
Inside a leaf, carbon and water get snapped together into sugar — the building block of wood. But it needs light for the energy. Slide all three up and watch the sugar bricks come together.
The leaf is making sugar — wood on the way!
4The big experiment — take one thing away
Weigh the plant and the soil, before and after 🌱
We start with plant mass 1 and soil mass 50 in equal model units. Light, water, and carbon dioxide are available. Predict how their mass changes compare over a season, then weigh them. These numbers illustrate a mass comparison, not a measured tree.
Guess before you find out
In this new season, the plant has light, water, and air. Will the plant gain more mass than the soil loses?