Atoms and molecules — Chemistry, 7–10 years
Everything around us is made from tiny building blocks. Atoms and molecules are too small to see, but they help us explain what materials are made of and why they behave differently.
The tiny building blocks
Imagine cutting a drop of water into smaller and smaller pieces. At some point, the pieces are made from water molecules, and each molecule contains even tinier atoms. We cannot see them with our eyes, but their arrangement helps make water, air, wood and plastic different.
Why imagine the invisible?
People needed an explanation for why a tiny amount of perfume can spread through a whole room, or why sugar seems to vanish in tea. The idea of tiny particles gave them one: matter is made of moving pieces too small to see. It is a model, not a photograph of the particles.
A water molecule
Start with the formula H₂O. The H means hydrogen and the small 2 means two hydrogen atoms. The O means one oxygen atom, so one water molecule contains two hydrogen atoms joined with one oxygen atom. Billions of these molecules make the water in a glass.
The visible drop
It is reasonable to think that one visible drop is one giant water particle, because the drop looks like one thing. In fact, it contains an enormous number of separate molecules, moving and bumping into one another. A model picture may show only a few molecules so we can count them.
Reading the world
Scientists use atoms and molecules to explain smells, medicines, cooking and materials such as strong fibres. For example, a smell reaches your nose when some molecules travel through the air. The particle model helps predict what may happen, but it does not replace testing the real material.
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