Chemical Reactions

A chemical reaction is a process where atoms in one or more substances, known as reactants, rearrange their structure by breaking the chemical bonds between their atoms and forming new bonds to create the products.

Consider the combustion of organic fuels. The molecules in the fuel, such as methane, react with oxygen to produce carbon dioxide and water. 

For all chemical reactions, the number of atoms of each element of reactants is balanced with the products they generate.

For example, one molecule of nitrogen gas reacts with three molecules of hydrogen gas to yield two molecules of ammonia, incorporating the two nitrogen and six hydrogens in the product.

Under certain theoretical conditions, all chemical reactions can be reversible. In this case, ammonia can decompose to form the reactants, as indicated by two opposite-headed arrows.

These forward and reverse reactions can occur simultaneously and, if not disturbed, eventually achieve an equilibrium state with no net change in the amounts of reactants and products.