What can we do? Can we change the subscripts in the formula for water so that it has two oxygen atoms in it? No you cannot change the formulas of individual substances because the chemical formula for a given substance is characteristic of that substance. But if we count the number of oxygen atoms in the reactants and products, we find that there are two oxygen atoms in the reactants but only one oxygen atom in the products. If we count the number of hydrogen atoms in the reactants and products, we find two hydrogen atoms. In chemical equations, the number of atoms of each element in the reactants must be the same as the number of atoms of each element in the products. The law of conservation of matter says that matter cannot be created or destroyed. Unfortunately, it is also an incomplete chemical equation. The initial substances are called reactants An initial substance in a chemical equation., and the final substances are called products A final substance in a chemical equation.
This is an example of a chemical equation A concise way of representing a chemical reaction., which is a concise way of representing a chemical reaction. Remembering that hydrogen and oxygen both exist as diatomic molecules, we can rewrite our chemical change as H 2 + O 2 → H 2O But substances can also be represented by chemical formulas. Where the + sign means that the two substances interact chemically with each other and the → symbol implies that a chemical reaction takes place. We can represent this chemical change more succinctly as hydrogen + oxygen → water We can write that as follows: hydrogen reacts with oxygen to make water For example, one chemical property of hydrogen is that it will react with oxygen to make water. Identify the parts of a chemical equation.Ī chemical reaction expresses a chemical change.