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

An endothermic reaction is defined as a chemical process that absorbs heat energy from its surroundings. This means that during the reaction, the reactants take in thermal energy, which typically results in a decrease in the temperature of the environment around the reaction. This is in contrast to exothermic reactions, which release heat energy.

In the context of the choices, the option that states a reaction in which heat energy is taken in accurately describes an endothermic reaction. By drawing thermal energy into the reaction, the products often have higher energy than the reactants, a fundamental aspect of endothermic processes. This concept is extensively observed in reactions such as photosynthesis, where plants absorb sunlight (heat energy) to convert carbon dioxide and water into glucose and oxygen.

Other options might describe different types of reactions or characteristics but do not capture the specific definition of an endothermic process, which revolves solely around the absorption of heat energy.