Molecules are two or more atoms stuck together. A molecule of water is two atoms of hydrogen bound to one atom of oxygen. Molecules are so tiny that we can t see them even with a powerful magnifying glass.
Chemists study molecules to see how they change, how they form, and how they move.
You are very familiar with the liquid, water. That s right. It is steam, like from a teakettle. It freezes, or gets colder. It gets hotter.