Air is all around us: we can feel it and see the different effects it has on objects in our environment.
Although air is a gas, it is made up of particles (like atoms and molecules), just like other materials.
Air is a mixture of gases which are vital for photosynthesis (how plants make food) and respiration (how organisms release energy from their food).
Battling against the wind uses lots of energy, so vehicle designers use shapes which reduce wind resistance, like this high-speed train.
Air can also be a very useful material: without a parachute, falling objects would accelerate to the ground and smash!
So, let's have a closer look at the air around us.