A chemical is a substance made up of atoms that are bonded together. Atoms are the elements on the periodic table, for example carbon, hydrogen, oxygen, nitrogen, and iron. There are 118 elements currently known. When elements bond, they join together and make a molecule. Chemicals are groups of molecules, and can be solid, liquids, or gases. Everything around you is made up of chemicals. Some chemicals you are pretty familiar with--water is chemical! One molecule of water is made of two hydrogen atoms and one oxygen atom, so we give it the chemical formula H₂O. The air you breathe is made up a chemicals like nitrogen, N₂, and oxygen, O₂. You need that oxygen in the air to survive!

Chemicals form both naturally and man-made. If you eat a plant like wheat or spinach, you're eating a whole bunch of complicated chemicals like carbohydrates and proteins that the plant made from sunlight, and other chemicals like carbon dioxide from the air. Your body uses the chemicals in food as fuel! Lots of man-made things are made from chemicals too, like plastic and clothes. While some chemicals can be bad for you, chemicals are all around you and are a part of your daily life, even if you don't realize it.