A plant is a living thing.  Plants have roots, a stem, and leaves.

Things can be solid, liquid, or a gas.  We cannot see a gas.  A gas fills things up like a balloon.  Air is a gas.

Air has oxygen.  Oxygen is part of a gas.  We breathe oxygen.  Plants give off oxygen.

Carbon dioxide is in air.  We breathe out carbon dioxide.  Plants take in carbon dioxide.

We use our lungs to breathe.  We take in air by breathing.  Air has oxygen.  Oxygen helps our bodies.