Some chemical formulas, like H2O (a.k.a. water), are almost as familiar to us as the words themselves. But why do we write them the way we do? The answer goes back to ...

Melting and freezing are both physical changes, which are often easy to reverse. To reverse this process, the water would need to be cooled enough until it freezes back into ice. This works because ...

Symbol equations are a quick way of representing chemical reactions. They show us what atoms are involved and how they are bonded together. Symbol equations always take the form, reactants → products.