In an exothermic reaction, there is a transfer of energy to the surroundings in the form of heat energy. The surroundings of the reaction will experience an increase in temperature. Many types of chemical reactions are exothermic, including combustion reactions, respiration and neutralization reactions of bases and acids.
One example of a combustion reaction is the burning of fuel. In this type of combustion reaction, a fuel like gasoline requires oxygen and produces the release of energy in the form of heat, carbon dioxide and water. All types of fire are further examples of combustion reactions.
Respiration is another example of the exothermic process. During respiration, glucose combines with the oxygen inhaled to produce water, carbon dioxide and energy. The food a person eats provides the carbohydrate or glucose needed for the reaction, and the air breathed in is the source of oxygen.
An acid/base neutralization process also is an exothermic reaction. For example, a strong acid like hydrochloric acid and a strong base like sodium hydroxide combine to produce water and sodium chloride, which is a type of salt.
However, an exothermic reaction is not the only type of chemical reaction. An endothermic reaction also is possible. An endothermic reaction occurs when energy is absorbed from the surroundings, causing a decrease in temperature.