* Matter has mass and takes up space. Leaves have mass (they weigh something) and they occupy a volume (they have a size).

* Matter is made of atoms. Leaves are composed of cells, which are made of molecules, which are made of atoms.

* Matter can change states. Leaves can be solid (when they're attached to a tree), liquid (when they decompose), or even gas (when they are burned).

So, leaves are a great example of matter!