Why air matters
Air is part of non-living nature and is everywhere: outdoors, indoors, in water and soil. All living things need air. It is transparent and colourless, so we cannot see it; it has no smell. Although light, air presses on everything on Earth: this is atmospheric pressure. Air carries sound, which is why we hear. It expands when warmed and contracts when cooled: this is how wind arises. Smoke from factories and vehicles pollutes air and makes breathing harder. We must keep the air clean.
Experiment “Dry paper”: fill a large clear basin with water. Press a crumpled paper ball into the bottom of a glass. Turn the glass upside down and push it straight down into the water. Lift it out and check the paper: it is dry! Why? The air in the glass keeps the water out. Safety: use an unbreakable cup and do not spill the water.