Exploring how water, air and light behave around us
Air is all around us even though we cannot see it. It takes up space, which is why a balloon grows when we blow into it, and moving air, called wind, can turn a pinwheel or push a sailboat. Air also pushes on things; this push is called air pressure. Water flows from higher places to lower places, which is why rivers run downhill and water comes out of a tap fixed low on a tank.
Some things float on water and others sink. A wooden block, a plastic bottle and a leaf float, while a stone and an iron nail sink. Light travels in straight lines and can pass through clear water and glass. When light passes from air into water it bends a little, so a straw in a glass of water looks broken at the surface. Sunlight passing through raindrops splits into seven colours to make a rainbow.
Why it matters
Knowing how air and water behave helps you understand kites, windmills, boats and why we store water in overhead tanks. Seeing how light bends explains rainbows and why a pond looks shallower than it really is. These simple ideas grow into topics like pressure, floatation and refraction of light in later classes.
Key terms
- Air pressure
- The push that air applies on everything around it.
- Float
- To stay on the surface of water without sinking.
- Rainbow
- A curved band of seven colours formed when sunlight passes through raindrops.