A Level Chemistry OCR Practice Exam

What happens to the energy in an exothermic reaction?

1. It is absorbed from the surroundings

2. It remains constant throughout the reaction

3. It is released into the surroundings

4. It is converted into electrical energy

The correct answer is: It is released into the surroundings

In an exothermic reaction, energy is released into the surroundings as a result of the chemical reaction occurring. This release of energy typically comes in the form of heat, which increases the temperature of the surroundings. The reason for this energy release lies in the breaking and formation of chemical bonds; the total energy of the products is less than that of the reactants, leading to a net release of energy. When reactants transform into products, the bonds formed in the products are stronger than those broken in the reactants, thus releasing energy. This characteristic is what distinguishes exothermic reactions from endothermic ones, where energy is taken in from the surroundings. Understanding this concept is fundamental in thermodynamics and helps explain why certain reactions, such as combustion or respiration, are exothermic, providing warmth and energy to their environment.