The atmosphere is the air around the Earth.  The atmosphere is made of gas.

Air is a gas.  Air has oxygen.  Air makes up the atmosphere around Earth.  We breathe air.  Air makes wind.

A gas is a kind of matter.  We usually cannot see gas.  Gas can fill things up like a balloon, a tire or a bubble.  Water heated can make a gas called steam.

Air has oxygen.  We breathe oxygen.  We need oxygen to live!

We breathe out carbon dioxide.  Plants take in carbon dioxide.