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

How can the energy change during an endothermic reaction be described?

1. Energy is neither created nor destroyed

2. Energy is absorbed from the surroundings

3. Energy is generated through combustion

4. Energy is released into the atmosphere

The correct answer is: Energy is absorbed from the surroundings

In an endothermic reaction, energy is absorbed from the surroundings, which causes the temperature of the surrounding environment to decrease. This characteristic fundamentally defines endothermic processes. During these reactions, the system takes in heat energy, which is necessary for the breaking of bonds within the reactants. The requirement of energy input distinguishes endothermic reactions from exothermic reactions, where energy is released instead. The concept of energy conservation, where energy is neither created nor destroyed, is a fundamental principle of thermodynamics that applies universally, including in endothermic reactions. However, this principle does not specifically address the absorption aspect that is critical to identifying endothermic reactions. Combustion processes typically relate to exothermic reactions, where energy is released rather than absorbed, making them incompatible with the definition of endothermic reactions. Similarly, stating that energy is released into the atmosphere contradicts the essential characteristic of endothermic reactions which involve absorption of energy, not its release.