# Chemical Reactions

## Chemical reactions

Chemical reactions occur when two or more atoms bond together to form molecules or when bonded atoms are broken apart. The substances that "go into" a chemical reaction are called the reactants (by convention, these are usually listed on the left side of a chemical equation), and the substances that are found to "come out" of the reaction are known as the products (by convention, these are usually found on the right side of a chemical equation). An arrow linking the reactants and products is typically drawn between them to indicate the direction of the chemical reaction. By convention, for one-way reactions, reactants are listed on the left and products on the right of the single-headed arrow. However, you should be able to identify reactants and products of one-way reactions that are written in any orientation (e.g., right-to-left, top-to-bottom, diagonal right-to-left, around a circular arrow, etc.)

$\underbrace{2H_2O_2}_{\text{hydrogen peroxide}} → \underbrace{2H_2O}_{\text{water}} + \underbrace{O_2}_{\text{oxygen}}$

Note: practice

Identify the reactants and products of the reaction involving hydrogen peroxide above.

Note: possible discussion

When we write $$H_2O_2$$ to represent the molecule hydrogen peroxide, it is a model representing an actual molecule. What information about the molecule is immediately communicated by this molecular formula? That is, what do you know about the molecule just by looking at the term $$H_2O_2$$?

$HCO_3^−+ H^+ \rightleftharpoons H_2CO_3 \label{2}$