The rate of reaction is the speed at which reactants are converted to products in a chemical reaction. It is an important topic in chemistry, as it can offer many important insights into the nature of various substances. This measurement is also important in industries that must produce some chemicals on a large scale, as the reactions that produce such chemicals must progress at a high enough rate. Some reactions may occur almost instantaneously while others may take hours, days, or even years to progress to completion. In academics, reaction rates are a subset of the topic of chemical kinetics, which is included under the title of physical chemistry.
There are many different factors that can affect the rate of a given reaction, with the nature of the reactants being only one. Temperature, for example, is important, as higher temperatures usually cause reactions to progress more quickly by providing more energy for the chemical system. The concentration of the reactants is also an important determining factor for reaction rate. Higher concentrations of reactants cause the reactants to collide with each other more frequently, thereby increasing the rate at which they react with each other.
One of the most important factors in the determination of the rate of reaction, particularly in biological systems, is the presence of a catalyst. Catalysts are molecules that increase the rate without being consumed by the reaction. They do so by lowering the activation energy that a reaction must overcome in order to progress. A certain amount of energy is required before a reaction can progress to completion, and catalysts decrease this amount of energy. Enzymes are biological proteins that are absolutely essential to most life, as many important chemical reactions that occur in animals would progress much too slowly without them.
Many mathematical methods have been developed to predict and to model the rate of a chemical reaction. These calculations are generally based on the concentration of the various reactants, the presence and precise nature of a catalyst, and the temperature, though other factors may also be considered. Some experimental data is generally needed to accurately determine an equation that can be used to predict the rate at any point. Generally speaking, chemical kinetics, rate of reaction, and the mathematics associated with them are taught in high school and college chemistry.