A Level Chemistry OCR Practice Exam 2025 – All-in-One Guide to Master Your Chemistry Exam!

In an endothermic reaction, energy is absorbed from the surroundings, typically in the form of heat. This absorption of heat causes the temperature of the surroundings to decrease. As a result, the enthalpy of the products becomes higher than that of the reactants, leading to an increase in the internal energy of the system. This characteristic distinguishes endothermic reactions from exothermic ones, where heat is released.

The other statements do not accurately describe the nature of endothermic reactions. For instance, suggesting that the enthalpy of the products is lower than that of the reactants contradicts the fundamental principle of an endothermic process. Similarly, the assertion that heat is released is characteristic of exothermic reactions, and the idea that the reaction occurs spontaneously without energy input does not generally apply to endothermic reactions, as they typically require energy input to proceed.