Chemical Reactions
When a chemical change occurs, we say a chemical reaction has taken place. A chemical reaction is the process in which one or more substances are changed into other substances. Chemical reactions are represented by chemical equations, which use numbers and formulas to keep track of the reactants and products. The reactants, or substances you start with, are written on the left side of the equation. The products, or substances you end up with, are written on the right side:
reactants → products
For example, coal is made mostly of carbon atoms. If coal is burned in air, the carbon atoms (reactants) combine with oxygen atoms (another reactant) from the air to produce carbon dioxide gas (the product). The equation for this chemical reaction is written:
carbon + oxygen → carbon dioxide
In the equation above, which substances are examples of elements and which is an example of a compound?