This question was asked by Elizabeth from West Sussex, UK.
Chemicals are everywhere. Everything made of matter (anything you can touch, eat, drink or breathe) is made from chemicals. Even people are made from chemicals! But to understand what they are, first we need to talk about atoms and elements. Atoms are the smallest distinct parts of matter, the basic building blocks that make up everything. Elements are what we call different kinds of atoms. Gold and oxygen are just two of the elements – so far scientists have discovered 118 elements and it’s believed that there are even more to be found.
So, back to chemicals. Well, chemicals can be made from any combination of atoms. A chemical could be a pure substance like iron or a mixture like air, which contains many different gaseous elements. A chemical could also be a compound like water, where two different elements join together to form a single unit. When atoms join together we also call them molecules.
One easy way of understanding elements and how they combine is to imagine the alphabet. There are only 26 letters in the English alphabet but they can be put together in millions of combinations. Chemical elements are the same. Here are a few you might encounter; notice how some of them contain the same elements even though they’re very different substances.
Helium = helium
Water = hydrogen and oxygen
Salt = sodium and chlorine
Chalk = calcium and carbon
Air = nitrogen, oxygen, carbon, argon, hydrogen
Sometimes you might hear people complaining about chemicals in food or other things. But now you know that absolutely everything is made from chemicals, whether it’s a tree, a cow, an apple – or you.
If you’re interested in how everyday words can have different meanings when they’re used in science, you might enjoy 12 Science Words That Don’t Mean What You Think They Do.