International General Certificate of Secondary Education (IGCSE) Chemistry Practice Exam

What happens to the energy during an exothermic reaction?

1. It is stored in the products

2. It is converted into mass

3. It is released into the surroundings

4. It is used to break chemical bonds

The correct answer is: It is released into the surroundings

In an exothermic reaction, the key characteristic is that energy is released into the surroundings. This energy release often occurs in the form of heat, leading to an increase in the surrounding temperature. During the process, the total energy of the products is lower than that of the reactants, as some of the energy stored in the chemical bonds of the reactants is transformed into heat energy. This release of energy is fundamental to the definition of exothermic reactions and is observable in various real-world examples, such as combustion reactions. The resulting temperature rise can be felt, making exothermic reactions easily identifiable based on their heat-generating properties. The other answers do not accurately describe the energy dynamics involved in exothermic reactions; for instance, energy being stored in the products contradicts the notion of energy release, while converting energy into mass or using it solely to break bonds does not capture the essence of how exothermic reactions operate.