In a chemical reaction, the substances that undergo change are called the reactants. The substances that are formed as a result of the reaction are called the products. The reactants and products are separated by an arrow in a chemical equation. For example, in the following equation, methane (CH₄) and oxygen (O₂) are the reactants, and carbon dioxide (CO₂) and water (H₂O) are the products:
CH₄ + 2O₂ → CO₂ + 2H₂O
The coefficients in front of the chemical formulas indicate the relative amounts of each substance that are involved in the reaction. In this case, one molecule of methane reacts with two molecules of oxygen to produce one molecule of carbon dioxide and two molecules of water.
The reactants and products in a chemical reaction are always different substances. This is because a chemical reaction involves a change in the chemical composition of the substances involved. In the above example, the methane and oxygen molecules are converted into carbon dioxide and water molecules. This change is due to the fact that the chemical bonds between the atoms in the reactants are broken and new bonds are formed between the atoms in the products.
Chemical reactions can be classified into several different types, including:
* Combination reactions: Two or more substances combine to form a single product. For example, when hydrogen and oxygen gases combine, they form water vapor.
* Decomposition reactions: A single substance breaks down into two or more products. For example, when water is electrolyzed, it breaks down into hydrogen and oxygen gases.
* Single-replacement reactions: One element replaces another element in a compound. For example, when iron is added to copper sulfate solution, the iron replaces the copper in the compound, forming iron sulfate and copper metal.
* Double-replacement reactions: Two compounds exchange ions to form two new compounds. For example, when sodium chloride and silver nitrate solutions are mixed, the sodium ions from the sodium chloride exchange places with the silver ions from the silver nitrate, forming sodium nitrate and silver chloride.
Chemical reactions are essential for life. They occur in our bodies, in the environment, and in the industries that produce the goods and services we use every day.
